Add <macro> tag to aapt2

AAPT2 Macros are compile-time resources definitions that are expanded
when referenced during the link phase.

A macro must be defined in the res/values.xml directory. A macro
definition for a macro named "foo" looks like the following:
 <macro name="foo">contents</macro>

When "@macro/foo" is used in the res/values directory or in a compiled
XML file, the contents of the macro replace the macro reference and
then the substituted contents are compiled and linked. If the macro
contents reference xml namespaces from its original definition, the
namespaces of the original macro definition will be used to determine
which package is being referenced.

Macros can be used anywhere resources can be referenced using the
@package:type/entry syntax.

Macros are not included in the final resource table or the R.java since
they are not actual resources.

Bug: 175616308
Test: aapt2_tests
Change-Id: I48b29ab6564357b32b4b4e32bff7ef06036382bc

33 files changed, 880 insertions, 260 deletions

diff --git a/tools/aapt2/Resource.cpp b/tools/aapt2/Resource.cpp
index b78f48ce7f17..6364ccdd09e5 100644
--- a/tools/aapt2/Resource.cpp
+++ b/tools/aapt2/Resource.cpp
@@ -78,6 +78,8 @@ StringPiece to_string(ResourceType type) {
       return "interpolator";
     case ResourceType::kLayout:
       return "layout";
+    case ResourceType::kMacro:
+      return "macro";
     case ResourceType::kMenu:
       return "menu";
     case ResourceType::kMipmap:
@@ -119,6 +121,7 @@ static const std::map<StringPiece, ResourceType> sResourceTypeMap{
     {"integer", ResourceType::kInteger},
     {"interpolator", ResourceType::kInterpolator},
     {"layout", ResourceType::kLayout},
+    {"macro", ResourceType::kMacro},
     {"menu", ResourceType::kMenu},
     {"mipmap", ResourceType::kMipmap},
     {"navigation", ResourceType::kNavigation},
diff --git a/tools/aapt2/Resource.h b/tools/aapt2/Resource.h
index cf938703e1e9..307c21d9dc96 100644
--- a/tools/aapt2/Resource.h
+++ b/tools/aapt2/Resource.h
@@ -57,6 +57,7 @@ enum class ResourceType {
   kInteger,
   kInterpolator,
   kLayout,
+  kMacro,
   kMenu,
   kMipmap,
   kNavigation,
diff --git a/tools/aapt2/ResourceParser.cpp b/tools/aapt2/ResourceParser.cpp
index 24c60b740bc3..1efabbb46fd5 100644
--- a/tools/aapt2/ResourceParser.cpp
+++ b/tools/aapt2/ResourceParser.cpp
@@ -627,6 +627,16 @@ bool ResourceParser::ParseResource(xml::XmlPullParser* parser,
     }
 
     return true;
+  } else if (resource_type == "macro") {
+    if (!maybe_name) {
+      diag_->Error(DiagMessage(out_resource->source)
+                   << "<" << parser->element_name() << "> missing 'name' attribute");
+      return false;
+    }
+
+    out_resource->name.type = ResourceType::kMacro;
+    out_resource->name.entry = maybe_name.value().to_string();
+    return ParseMacro(parser, out_resource);
   }
 
   if (can_be_item) {
@@ -726,6 +736,24 @@ bool ResourceParser::ParseItem(xml::XmlPullParser* parser,
   return true;
 }
 
+std::optional<FlattenedXmlSubTree> ResourceParser::CreateFlattenSubTree(
+    xml::XmlPullParser* parser) {
+  const size_t begin_xml_line = parser->line_number();
+
+  std::string raw_value;
+  StyleString style_string;
+  std::vector<UntranslatableSection> untranslatable_sections;
+  if (!FlattenXmlSubtree(parser, &raw_value, &style_string, &untranslatable_sections)) {
+    return {};
+  }
+
+  return FlattenedXmlSubTree{.raw_value = raw_value,
+                             .style_string = style_string,
+                             .untranslatable_sections = untranslatable_sections,
+                             .namespace_resolver = parser,
+                             .source = source_.WithLine(begin_xml_line)};
+}
+
 /**
  * Reads the entire XML subtree and attempts to parse it as some Item,
  * with typeMask denoting which items it can be. If allowRawValue is
@@ -733,42 +761,46 @@ bool ResourceParser::ParseItem(xml::XmlPullParser* parser,
  * an Item. If allowRawValue is false, nullptr is returned in this
  * case.
  */
-std::unique_ptr<Item> ResourceParser::ParseXml(xml::XmlPullParser* parser,
-                                               const uint32_t type_mask,
+std::unique_ptr<Item> ResourceParser::ParseXml(xml::XmlPullParser* parser, const uint32_t type_mask,
                                                const bool allow_raw_value) {
-  const size_t begin_xml_line = parser->line_number();
-
-  std::string raw_value;
-  StyleString style_string;
-  std::vector<UntranslatableSection> untranslatable_sections;
-  if (!FlattenXmlSubtree(parser, &raw_value, &style_string, &untranslatable_sections)) {
+  auto sub_tree = CreateFlattenSubTree(parser);
+  if (!sub_tree.has_value()) {
     return {};
   }
+  return ParseXml(sub_tree.value(), type_mask, allow_raw_value, *table_, config_, *diag_);
+}
 
-  if (!style_string.spans.empty()) {
+std::unique_ptr<Item> ResourceParser::ParseXml(const FlattenedXmlSubTree& xmlsub_tree,
+                                               const uint32_t type_mask, const bool allow_raw_value,
+                                               ResourceTable& table,
+                                               const android::ConfigDescription& config,
+                                               IDiagnostics& diag) {
+  if (!xmlsub_tree.style_string.spans.empty()) {
     // This can only be a StyledString.
     std::unique_ptr<StyledString> styled_string =
-        util::make_unique<StyledString>(table_->string_pool.MakeRef(
-            style_string, StringPool::Context(StringPool::Context::kNormalPriority, config_)));
-    styled_string->untranslatable_sections = std::move(untranslatable_sections);
+        util::make_unique<StyledString>(table.string_pool.MakeRef(
+            xmlsub_tree.style_string,
+            StringPool::Context(StringPool::Context::kNormalPriority, config)));
+    styled_string->untranslatable_sections = xmlsub_tree.untranslatable_sections;
     return std::move(styled_string);
   }
 
   auto on_create_reference = [&](const ResourceName& name) {
     // name.package can be empty here, as it will assume the package name of the
     // table.
-    std::unique_ptr<Id> id = util::make_unique<Id>();
-    id->SetSource(source_.WithLine(begin_xml_line));
-    table_->AddResource(NewResourceBuilder(name).SetValue(std::move(id)).Build(), diag_);
+    auto id = util::make_unique<Id>();
+    id->SetSource(xmlsub_tree.source);
+    return table.AddResource(NewResourceBuilder(name).SetValue(std::move(id)).Build(), &diag);
   };
 
   // Process the raw value.
-  std::unique_ptr<Item> processed_item =
-      ResourceUtils::TryParseItemForAttribute(raw_value, type_mask, on_create_reference);
+  std::unique_ptr<Item> processed_item = ResourceUtils::TryParseItemForAttribute(
+      xmlsub_tree.raw_value, type_mask, on_create_reference);
   if (processed_item) {
     // Fix up the reference.
-    if (Reference* ref = ValueCast<Reference>(processed_item.get())) {
-      ResolvePackage(parser, ref);
+    if (auto ref = ValueCast<Reference>(processed_item.get())) {
+      ref->allow_raw = allow_raw_value;
+      ResolvePackage(xmlsub_tree.namespace_resolver, ref);
     }
     return processed_item;
   }
@@ -777,17 +809,16 @@ std::unique_ptr<Item> ResourceParser::ParseXml(xml::XmlPullParser* parser,
   if (type_mask & android::ResTable_map::TYPE_STRING) {
     // Use the trimmed, escaped string.
     std::unique_ptr<String> string = util::make_unique<String>(
-        table_->string_pool.MakeRef(style_string.str, StringPool::Context(config_)));
-    string->untranslatable_sections = std::move(untranslatable_sections);
+        table.string_pool.MakeRef(xmlsub_tree.style_string.str, StringPool::Context(config)));
+    string->untranslatable_sections = xmlsub_tree.untranslatable_sections;
     return std::move(string);
   }
 
   if (allow_raw_value) {
     // We can't parse this so return a RawString if we are allowed.
-    return util::make_unique<RawString>(
-        table_->string_pool.MakeRef(util::TrimWhitespace(raw_value),
-                                    StringPool::Context(config_)));
-  } else if (util::TrimWhitespace(raw_value).empty()) {
+    return util::make_unique<RawString>(table.string_pool.MakeRef(
+        util::TrimWhitespace(xmlsub_tree.raw_value), StringPool::Context(config)));
+  } else if (util::TrimWhitespace(xmlsub_tree.raw_value).empty()) {
     // If the text is empty, and the value is not allowed to be a string, encode it as a @null.
     return ResourceUtils::MakeNull();
   }
@@ -850,6 +881,35 @@ bool ResourceParser::ParseString(xml::XmlPullParser* parser,
   return true;
 }
 
+bool ResourceParser::ParseMacro(xml::XmlPullParser* parser, ParsedResource* out_resource) {
+  auto sub_tree = CreateFlattenSubTree(parser);
+  if (!sub_tree) {
+    return false;
+  }
+
+  if (out_resource->config != ConfigDescription::DefaultConfig()) {
+    diag_->Error(DiagMessage(out_resource->source)
+                 << "<macro> tags cannot be declared in configurations other than the default "
+                    "configuration'");
+    return false;
+  }
+
+  auto macro = std::make_unique<Macro>();
+  macro->raw_value = std::move(sub_tree->raw_value);
+  macro->style_string = std::move(sub_tree->style_string);
+  macro->untranslatable_sections = std::move(sub_tree->untranslatable_sections);
+
+  for (const auto& decl : parser->package_decls()) {
+    macro->alias_namespaces.emplace_back(
+        Macro::Namespace{.alias = decl.prefix,
+                         .package_name = decl.package.package,
+                         .is_private = decl.package.private_namespace});
+  }
+
+  out_resource->value = std::move(macro);
+  return true;
+}
+
 bool ResourceParser::ParsePublic(xml::XmlPullParser* parser, ParsedResource* out_resource) {
   if (options_.visibility) {
     diag_->Error(DiagMessage(out_resource->source)
diff --git a/tools/aapt2/ResourceParser.h b/tools/aapt2/ResourceParser.h
index af0db8c0ba2c..5c92def50616 100644
--- a/tools/aapt2/ResourceParser.h
+++ b/tools/aapt2/ResourceParser.h
@@ -57,6 +57,14 @@ struct ResourceParserOptions {
   Maybe<Visibility::Level> visibility;
 };
 
+struct FlattenedXmlSubTree {
+  std::string raw_value;
+  StyleString style_string;
+  std::vector<UntranslatableSection> untranslatable_sections;
+  xml::IPackageDeclStack* namespace_resolver;
+  Source source;
+};
+
 /*
  * Parses an XML file for resources and adds them to a ResourceTable.
  */
@@ -67,9 +75,16 @@ class ResourceParser {
                  const ResourceParserOptions& options = {});
   bool Parse(xml::XmlPullParser* parser);
 
+  static std::unique_ptr<Item> ParseXml(const FlattenedXmlSubTree& xmlsub_tree, uint32_t type_mask,
+                                        bool allow_raw_value, ResourceTable& table,
+                                        const android::ConfigDescription& config,
+                                        IDiagnostics& diag);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(ResourceParser);
 
+  std::optional<FlattenedXmlSubTree> CreateFlattenSubTree(xml::XmlPullParser* parser);
+
   // Parses the XML subtree as a StyleString (flattened XML representation for strings with
   // formatting). If parsing fails, false is returned and the out parameters are left in an
   // unspecified state. Otherwise,
@@ -96,7 +111,7 @@ class ResourceParser {
 
   bool ParseItem(xml::XmlPullParser* parser, ParsedResource* out_resource, uint32_t format);
   bool ParseString(xml::XmlPullParser* parser, ParsedResource* out_resource);
-
+  bool ParseMacro(xml::XmlPullParser* parser, ParsedResource* out_resource);
   bool ParsePublic(xml::XmlPullParser* parser, ParsedResource* out_resource);
   bool ParsePublicGroup(xml::XmlPullParser* parser, ParsedResource* out_resource);
   bool ParseStagingPublicGroup(xml::XmlPullParser* parser, ParsedResource* out_resource);
@@ -108,8 +123,7 @@ class ResourceParser {
   bool ParseAttrImpl(xml::XmlPullParser* parser, ParsedResource* out_resource, bool weak);
   Maybe<Attribute::Symbol> ParseEnumOrFlagItem(xml::XmlPullParser* parser,
                                                const android::StringPiece& tag);
-  bool ParseStyle(const ResourceType type, xml::XmlPullParser* parser,
-                  ParsedResource* out_resource);
+  bool ParseStyle(ResourceType type, xml::XmlPullParser* parser, ParsedResource* out_resource);
   bool ParseStyleItem(xml::XmlPullParser* parser, Style* style);
   bool ParseDeclareStyleable(xml::XmlPullParser* parser, ParsedResource* out_resource);
   bool ParseArray(xml::XmlPullParser* parser, ParsedResource* out_resource);
diff --git a/tools/aapt2/ResourceParser_test.cpp b/tools/aapt2/ResourceParser_test.cpp
index 4a509be56776..279ebcba2f71 100644
--- a/tools/aapt2/ResourceParser_test.cpp
+++ b/tools/aapt2/ResourceParser_test.cpp
@@ -336,6 +336,90 @@ TEST_F(ResourceParserTest, ParseAttr) {
   EXPECT_THAT(attr->type_mask, Eq(ResTable_map::TYPE_ANY));
 }
 
+TEST_F(ResourceParserTest, ParseMacro) {
+  std::string input = R"(<macro name="foo">12345</macro>)";
+  ASSERT_TRUE(TestParse(input));
+
+  Macro* macro = test::GetValue<Macro>(&table_, "macro/foo");
+  ASSERT_THAT(macro, NotNull());
+  EXPECT_THAT(macro->raw_value, Eq("12345"));
+  EXPECT_THAT(macro->style_string.str, Eq("12345"));
+  EXPECT_THAT(macro->style_string.spans, IsEmpty());
+  EXPECT_THAT(macro->untranslatable_sections, IsEmpty());
+  EXPECT_THAT(macro->alias_namespaces, IsEmpty());
+}
+
+TEST_F(ResourceParserTest, ParseMacroUntranslatableSection) {
+  std::string input = R"(<macro name="foo" xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
+This being <b><xliff:g>human</xliff:g></b> is a guest house.</macro>)";
+  ASSERT_TRUE(TestParse(input));
+
+  Macro* macro = test::GetValue<Macro>(&table_, "macro/foo");
+  ASSERT_THAT(macro, NotNull());
+  EXPECT_THAT(macro->raw_value, Eq("\nThis being human is a guest house."));
+  EXPECT_THAT(macro->style_string.str, Eq(" This being human is a guest house."));
+  EXPECT_THAT(macro->style_string.spans.size(), Eq(1));
+  EXPECT_THAT(macro->style_string.spans[0].name, Eq("b"));
+  EXPECT_THAT(macro->style_string.spans[0].first_char, Eq(12));
+  EXPECT_THAT(macro->style_string.spans[0].last_char, Eq(16));
+  ASSERT_THAT(macro->untranslatable_sections.size(), Eq(1));
+  EXPECT_THAT(macro->untranslatable_sections[0].start, Eq(12));
+  EXPECT_THAT(macro->untranslatable_sections[0].end, Eq(17));
+  EXPECT_THAT(macro->alias_namespaces, IsEmpty());
+}
+
+TEST_F(ResourceParserTest, ParseMacroNamespaces) {
+  std::string input = R"(<macro name="foo" xmlns:app="http://schemas.android.com/apk/res/android">
+@app:string/foo</macro>)";
+  ASSERT_TRUE(TestParse(input));
+
+  Macro* macro = test::GetValue<Macro>(&table_, "macro/foo");
+  ASSERT_THAT(macro, NotNull());
+  EXPECT_THAT(macro->raw_value, Eq("\n@app:string/foo"));
+  EXPECT_THAT(macro->style_string.str, Eq("@app:string/foo"));
+  EXPECT_THAT(macro->style_string.spans, IsEmpty());
+  EXPECT_THAT(macro->untranslatable_sections, IsEmpty());
+  EXPECT_THAT(macro->alias_namespaces.size(), Eq(1));
+  EXPECT_THAT(macro->alias_namespaces[0].alias, Eq("app"));
+  EXPECT_THAT(macro->alias_namespaces[0].package_name, Eq("android"));
+  EXPECT_THAT(macro->alias_namespaces[0].is_private, Eq(false));
+}
+
+TEST_F(ResourceParserTest, ParseMacroReference) {
+  std::string input = R"(<string name="res_string">@macro/foo</string>)";
+  ASSERT_TRUE(TestParse(input));
+
+  Reference* macro = test::GetValue<Reference>(&table_, "string/res_string");
+  ASSERT_THAT(macro, NotNull());
+  EXPECT_THAT(macro->type_flags, Eq(ResTable_map::TYPE_STRING));
+  EXPECT_THAT(macro->allow_raw, Eq(false));
+
+  input = R"(<style name="foo">
+               <item name="bar">@macro/foo</item>
+             </style>)";
+
+  ASSERT_TRUE(TestParse(input));
+  Style* style = test::GetValue<Style>(&table_, "style/foo");
+  ASSERT_THAT(style, NotNull());
+  EXPECT_THAT(style->entries.size(), Eq(1));
+
+  macro = ValueCast<Reference>(style->entries[0].value.get());
+  ASSERT_THAT(macro, NotNull());
+  EXPECT_THAT(macro->type_flags, Eq(0U));
+  EXPECT_THAT(macro->allow_raw, Eq(true));
+}
+
+TEST_F(ResourceParserTest, ParseMacroNoNameFail) {
+  std::string input = R"(<macro>12345</macro>)";
+  ASSERT_FALSE(TestParse(input));
+}
+
+TEST_F(ResourceParserTest, ParseMacroNonDefaultConfigurationFail) {
+  const ConfigDescription watch_config = test::ParseConfigOrDie("watch");
+  std::string input = R"(<macro name="foo">12345</macro>)";
+  ASSERT_FALSE(TestParse(input, watch_config));
+}
+
 // Old AAPT allowed attributes to be defined under different configurations, but ultimately
 // stored them with the default configuration. Check that we have the same behavior.
 TEST_F(ResourceParserTest, ParseAttrAndDeclareStyleableUnderConfigButRecordAsNoConfig) {
diff --git a/tools/aapt2/ResourceUtils.cpp b/tools/aapt2/ResourceUtils.cpp
index 5b43df6f0935..e0e80ac02dea 100644
--- a/tools/aapt2/ResourceUtils.cpp
+++ b/tools/aapt2/ResourceUtils.cpp
@@ -628,7 +628,7 @@ uint32_t AndroidTypeToAttributeTypeMask(uint16_t type) {
 
 std::unique_ptr<Item> TryParseItemForAttribute(
     const StringPiece& value, uint32_t type_mask,
-    const std::function<void(const ResourceName&)>& on_create_reference) {
+    const std::function<bool(const ResourceName&)>& on_create_reference) {
   using android::ResTable_map;
 
   auto null_or_empty = TryParseNullOrEmpty(value);
@@ -639,8 +639,11 @@ std::unique_ptr<Item> TryParseItemForAttribute(
   bool create = false;
   auto reference = TryParseReference(value, &create);
   if (reference) {
+    reference->type_flags = type_mask;
     if (create && on_create_reference) {
-      on_create_reference(reference->name.value());
+      if (!on_create_reference(reference->name.value())) {
+        return {};
+      }
     }
     return std::move(reference);
   }
@@ -689,7 +692,7 @@ std::unique_ptr<Item> TryParseItemForAttribute(
  */
 std::unique_ptr<Item> TryParseItemForAttribute(
     const StringPiece& str, const Attribute* attr,
-    const std::function<void(const ResourceName&)>& on_create_reference) {
+    const std::function<bool(const ResourceName&)>& on_create_reference) {
   using android::ResTable_map;
 
   const uint32_t type_mask = attr->type_mask;
diff --git a/tools/aapt2/ResourceUtils.h b/tools/aapt2/ResourceUtils.h
index f77766ee9061..be493db8cee0 100644
--- a/tools/aapt2/ResourceUtils.h
+++ b/tools/aapt2/ResourceUtils.h
@@ -204,11 +204,11 @@ std::unique_ptr<BinaryPrimitive> TryParseFlagSymbol(const Attribute* enum_attr,
  */
 std::unique_ptr<Item> TryParseItemForAttribute(
     const android::StringPiece& value, const Attribute* attr,
-    const std::function<void(const ResourceName&)>& on_create_reference = {});
+    const std::function<bool(const ResourceName&)>& on_create_reference = {});
 
 std::unique_ptr<Item> TryParseItemForAttribute(
     const android::StringPiece& value, uint32_t type_mask,
-    const std::function<void(const ResourceName&)>& on_create_reference = {});
+    const std::function<bool(const ResourceName&)>& on_create_reference = {});
 
 uint32_t AndroidTypeToAttributeTypeMask(uint16_t type);
 
diff --git a/tools/aapt2/ResourceValues.cpp b/tools/aapt2/ResourceValues.cpp
index 574bd2e44a84..2a90f267f185 100644
--- a/tools/aapt2/ResourceValues.cpp
+++ b/tools/aapt2/ResourceValues.cpp
@@ -111,12 +111,15 @@ bool Reference::Equals(const Value* value) const {
   if (!other) {
     return false;
   }
-  return reference_type == other->reference_type &&
-         private_reference == other->private_reference && id == other->id &&
-         name == other->name;
+  return reference_type == other->reference_type && private_reference == other->private_reference &&
+         id == other->id && name == other->name && type_flags == other->type_flags;
 }
 
 bool Reference::Flatten(android::Res_value* out_value) const {
+  if (name && name.value().type == ResourceType::kMacro) {
+    return false;
+  }
+
   const ResourceId resid = id.value_or_default(ResourceId(0));
   const bool dynamic = resid.is_valid() && is_dynamic;
 
@@ -551,7 +554,7 @@ bool Attribute::IsCompatibleWith(const Attribute& attr) const {
   return this_type_mask == that_type_mask;
 }
 
-std::string Attribute::MaskString() const {
+std::string Attribute::MaskString(uint32_t type_mask) {
   if (type_mask == android::ResTable_map::TYPE_ANY) {
     return "any";
   }
@@ -650,6 +653,10 @@ std::string Attribute::MaskString() const {
   return out.str();
 }
 
+std::string Attribute::MaskString() const {
+  return MaskString(type_mask);
+}
+
 void Attribute::Print(std::ostream* out) const {
   *out << "(attr) " << MaskString();
 
@@ -1017,6 +1024,21 @@ void Styleable::Print(std::ostream* out) const {
        << " [" << util::Joiner(entries, ", ") << "]";
 }
 
+bool Macro::Equals(const Value* value) const {
+  const Macro* other = ValueCast<Macro>(value);
+  if (!other) {
+    return false;
+  }
+  return other->raw_value == raw_value && other->style_string.spans == style_string.spans &&
+         other->style_string.str == style_string.str &&
+         other->untranslatable_sections == untranslatable_sections &&
+         other->alias_namespaces == alias_namespaces;
+}
+
+void Macro::Print(std::ostream* out) const {
+  *out << "(macro) ";
+}
+
 bool operator<(const Reference& a, const Reference& b) {
   int cmp = a.name.value_or_default({}).compare(b.name.value_or_default({}));
   if (cmp != 0) return cmp < 0;
@@ -1149,4 +1171,9 @@ std::unique_ptr<Styleable> CloningValueTransformer::TransformDerived(const Style
   return CopyValueFields(std::move(new_value), value);
 }
 
+std::unique_ptr<Macro> CloningValueTransformer::TransformDerived(const Macro* value) {
+  auto new_value = std::make_unique<Macro>(*value);
+  return CopyValueFields(std::move(new_value), value);
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/ResourceValues.h b/tools/aapt2/ResourceValues.h
index 025864d385cf..d11b013f14d5 100644
--- a/tools/aapt2/ResourceValues.h
+++ b/tools/aapt2/ResourceValues.h
@@ -164,6 +164,8 @@ struct Reference : public TransformableItem<Reference, BaseItem<Reference>> {
   Reference::Type reference_type;
   bool private_reference = false;
   bool is_dynamic = false;
+  std::optional<uint32_t> type_flags;
+  bool allow_raw;
 
   Reference();
   explicit Reference(const ResourceNameRef& n, Type type = Type::kResource);
@@ -311,6 +313,8 @@ struct Attribute : public TransformableValue<Attribute, BaseValue<Attribute>> {
   bool IsCompatibleWith(const Attribute& attr) const;
 
   std::string MaskString() const;
+  static std::string MaskString(uint32_t type_mask);
+
   void Print(std::ostream* out) const override;
   bool Matches(const Item& item, DiagMessage* out_msg = nullptr) const;
 };
@@ -362,6 +366,28 @@ struct Styleable : public TransformableValue<Styleable, BaseValue<Styleable>> {
   void MergeWith(Styleable* styleable);
 };
 
+struct Macro : public TransformableValue<Macro, BaseValue<Macro>> {
+  std::string raw_value;
+  StyleString style_string;
+  std::vector<UntranslatableSection> untranslatable_sections;
+
+  struct Namespace {
+    std::string alias;
+    std::string package_name;
+    bool is_private;
+
+    bool operator==(const Namespace& right) const {
+      return alias == right.alias && package_name == right.package_name &&
+             is_private == right.is_private;
+    }
+  };
+
+  std::vector<Namespace> alias_namespaces;
+
+  bool Equals(const Value* value) const override;
+  void Print(std::ostream* out) const override;
+};
+
 template <typename T>
 typename std::enable_if<std::is_base_of<Value, T>::value, std::ostream&>::type operator<<(
     std::ostream& out, const std::unique_ptr<T>& value) {
@@ -388,6 +414,7 @@ struct CloningValueTransformer : public ValueTransformer {
   std::unique_ptr<Array> TransformDerived(const Array* value) override;
   std::unique_ptr<Plural> TransformDerived(const Plural* value) override;
   std::unique_ptr<Styleable> TransformDerived(const Styleable* value) override;
+  std::unique_ptr<Macro> TransformDerived(const Macro* value) override;
 };
 
 }  // namespace aapt
diff --git a/tools/aapt2/Resources.proto b/tools/aapt2/Resources.proto
index 4247ec5a3495..b45c0401d19a 100644
--- a/tools/aapt2/Resources.proto
+++ b/tools/aapt2/Resources.proto
@@ -273,6 +273,7 @@ message CompoundValue {
     Styleable styleable = 3;
     Array array = 4;
     Plural plural = 5;
+    MacroBody macro = 6;
   }
 }
 
@@ -304,6 +305,13 @@ message Reference {
 
   // Whether this reference is dynamic.
   Boolean is_dynamic = 5;
+
+  // The type flags used when compiling the reference. Used for substituting the contents of macros.
+  uint32 type_flags = 6;
+
+  // Whether raw string values would have been accepted in place of this reference definition. Used
+  // for substituting the contents of macros.
+  bool allow_raw = 7;
 }
 
 // A value that represents an ID. This is just a placeholder, as ID values are used to occupy a
@@ -591,3 +599,32 @@ message XmlAttribute {
   // The optional interpreted/compiled version of the `value` string.
   Item compiled_item = 6;
 }
+
+message MacroBody {
+  string raw_string = 1;
+  StyleString style_string = 2;
+  repeated UntranslatableSection untranslatable_sections = 3;
+  repeated NamespaceAlias namespace_stack = 4;
+  SourcePosition source = 5;
+}
+
+message NamespaceAlias {
+  string prefix = 1;
+  string package_name = 2;
+  bool is_private = 3;
+}
+
+message StyleString {
+  message Span {
+    string name = 1;
+    uint32 start_index = 2;
+    uint32 end_index = 3;
+  }
+  string str = 1;
+  repeated Span spans = 2;
+}
+
+message UntranslatableSection {
+  uint64 start_index = 1;
+  uint64 end_index = 2;
+}
\ No newline at end of file
diff --git a/tools/aapt2/StringPool.h b/tools/aapt2/StringPool.h
index 1006ca970dc5..3457e0b41859 100644
--- a/tools/aapt2/StringPool.h
+++ b/tools/aapt2/StringPool.h
@@ -36,6 +36,10 @@ struct Span {
   std::string name;
   uint32_t first_char;
   uint32_t last_char;
+
+  bool operator==(const Span& right) const {
+    return name == right.name && first_char == right.first_char && last_char == right.last_char;
+  }
 };
 
 struct StyleString {
diff --git a/tools/aapt2/ValueTransformer.cpp b/tools/aapt2/ValueTransformer.cpp
index 6eb2e30fb923..2d7996b9d880 100644
--- a/tools/aapt2/ValueTransformer.cpp
+++ b/tools/aapt2/ValueTransformer.cpp
@@ -46,5 +46,6 @@ VALUE_CREATE_VALUE_DECL(Style);
 VALUE_CREATE_VALUE_DECL(Array);
 VALUE_CREATE_VALUE_DECL(Plural);
 VALUE_CREATE_VALUE_DECL(Styleable);
+VALUE_CREATE_VALUE_DECL(Macro);
 
 }  // namespace aapt
\ No newline at end of file
diff --git a/tools/aapt2/ValueTransformer.h b/tools/aapt2/ValueTransformer.h
index 692511132012..6fc4a191b04b 100644
--- a/tools/aapt2/ValueTransformer.h
+++ b/tools/aapt2/ValueTransformer.h
@@ -37,6 +37,7 @@ struct Style;
 struct Array;
 struct Plural;
 struct Styleable;
+struct Macro;
 
 #define AAPT_TRANSFORM_VALUE(T)                                    \
   virtual std::unique_ptr<T> TransformDerived(const T* value) = 0; \
@@ -97,6 +98,7 @@ struct ValueTransformer {
   AAPT_TRANSFORM_VALUE(Array);
   AAPT_TRANSFORM_VALUE(Plural);
   AAPT_TRANSFORM_VALUE(Styleable);
+  AAPT_TRANSFORM_VALUE(Macro);
 
  protected:
   StringPool* const pool_;
diff --git a/tools/aapt2/ValueVisitor.h b/tools/aapt2/ValueVisitor.h
index 4e74ec366dab..d0c9d89b6f0c 100644
--- a/tools/aapt2/ValueVisitor.h
+++ b/tools/aapt2/ValueVisitor.h
@@ -43,6 +43,9 @@ class ValueVisitor {
   virtual void Visit(Array* value) { VisitAny(value); }
   virtual void Visit(Plural* value) { VisitAny(value); }
   virtual void Visit(Styleable* value) { VisitAny(value); }
+  virtual void Visit(Macro* value) {
+    VisitAny(value);
+  }
 };
 
 // Const version of ValueVisitor.
@@ -92,6 +95,9 @@ class ConstValueVisitor {
   virtual void Visit(const Styleable* value) {
     VisitAny(value);
   }
+  virtual void Visit(const Macro* value) {
+    VisitAny(value);
+  }
 };
 
 // NOLINT, do not add parentheses around T.
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index 2c57fb2b003e..e4d0f3b6bd23 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -462,7 +462,7 @@ std::vector<std::unique_ptr<xml::XmlResource>> ResourceFileFlattener::LinkAndVer
   // that existing projects have out-of-date references which pass compilation.
   xml::StripAndroidStudioAttributes(doc->root.get());
 
-  XmlReferenceLinker xml_linker;
+  XmlReferenceLinker xml_linker(table);
   if (!options_.do_not_fail_on_missing_resources && !xml_linker.Consume(context_, doc)) {
     return {};
   }
@@ -2112,7 +2112,7 @@ class Linker {
         std::unique_ptr<xml::XmlResource> split_manifest =
             GenerateSplitManifest(app_info_, *split_constraints_iter);
 
-        XmlReferenceLinker linker;
+        XmlReferenceLinker linker(&final_table_);
         if (!linker.Consume(context_, split_manifest.get())) {
           context_->GetDiagnostics()->Error(DiagMessage()
                                             << "failed to create Split AndroidManifest.xml");
@@ -2143,7 +2143,7 @@ class Linker {
       // So we give it a package name so it can see local resources.
       manifest_xml->file.name.package = context_->GetCompilationPackage();
 
-      XmlReferenceLinker manifest_linker;
+      XmlReferenceLinker manifest_linker(&final_table_);
       if (options_.merge_only || manifest_linker.Consume(context_, manifest_xml.get())) {
         if (options_.generate_proguard_rules_path &&
             !proguard::CollectProguardRulesForManifest(manifest_xml.get(), &proguard_keep_set)) {
diff --git a/tools/aapt2/cmd/Link_test.cpp b/tools/aapt2/cmd/Link_test.cpp
index d1e6d3922f3f..3118eb8f7731 100644
--- a/tools/aapt2/cmd/Link_test.cpp
+++ b/tools/aapt2/cmd/Link_test.cpp
@@ -24,6 +24,7 @@
 
 using testing::Eq;
 using testing::HasSubstr;
+using testing::IsNull;
 using testing::Ne;
 using testing::NotNull;
 
@@ -532,4 +533,109 @@ TEST_F(LinkTest, StagedAndroidApi) {
   EXPECT_THAT(*result, Eq(0x01fd0072));
 }
 
+TEST_F(LinkTest, MacroSubstitution) {
+  StdErrDiagnostics diag;
+  const std::string values =
+      R"(<resources xmlns:an="http://schemas.android.com/apk/res/android">
+           <macro name="is_enabled">true</macro>
+           <macro name="deep_is_enabled">@macro/is_enabled</macro>
+           <macro name="attr_ref">?is_enabled_attr</macro>
+           <macro name="raw_string">Hello World!</macro>
+           <macro name="android_ref">@an:color/primary_text_dark</macro>
+
+           <attr name="is_enabled_attr" />
+           <public type="attr" name="is_enabled_attr" id="0x7f010000"/>
+
+           <string name="is_enabled_str">@macro/is_enabled</string>
+           <bool name="is_enabled_bool">@macro/deep_is_enabled</bool>
+
+           <array name="my_array">
+             <item>@macro/is_enabled</item>
+           </array>
+
+           <style name="MyStyle">
+              <item name="android:background">@macro/attr_ref</item>
+              <item name="android:fontFamily">@macro/raw_string</item>
+           </style>
+         </resources>)";
+
+  const std::string xml_values =
+      R"(<SomeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+                     android:background="@macro/android_ref"
+                     android:fontFamily="@macro/raw_string">
+         </SomeLayout>)";
+
+  // Build a library with a public attribute
+  const std::string lib_res = GetTestPath("test-res");
+  ASSERT_TRUE(CompileFile(GetTestPath("res/values/values.xml"), values, lib_res, &diag));
+  ASSERT_TRUE(CompileFile(GetTestPath("res/layout/layout.xml"), xml_values, lib_res, &diag));
+
+  const std::string lib_apk = GetTestPath("test.apk");
+  // clang-format off
+  auto lib_link_args = LinkCommandBuilder(this)
+      .SetManifestFile(ManifestBuilder(this).SetPackageName("com.test").Build())
+      .AddCompiledResDir(lib_res, &diag)
+      .AddFlag("--no-auto-version")
+      .Build(lib_apk);
+  // clang-format on
+  ASSERT_TRUE(Link(lib_link_args, &diag));
+
+  auto apk = LoadedApk::LoadApkFromPath(lib_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+
+  // Test that the type flags determines the value type
+  auto actual_bool =
+      test::GetValue<BinaryPrimitive>(apk->GetResourceTable(), "com.test:bool/is_enabled_bool");
+  ASSERT_THAT(actual_bool, NotNull());
+  EXPECT_EQ(android::Res_value::TYPE_INT_BOOLEAN, actual_bool->value.dataType);
+  EXPECT_EQ(0xffffffffu, actual_bool->value.data);
+
+  auto actual_str =
+      test::GetValue<String>(apk->GetResourceTable(), "com.test:string/is_enabled_str");
+  ASSERT_THAT(actual_str, NotNull());
+  EXPECT_EQ(*actual_str->value, "true");
+
+  // Test nested data structures
+  auto actual_array = test::GetValue<Array>(apk->GetResourceTable(), "com.test:array/my_array");
+  ASSERT_THAT(actual_array, NotNull());
+  EXPECT_THAT(actual_array->elements.size(), Eq(1));
+
+  auto array_el_ref = ValueCast<BinaryPrimitive>(actual_array->elements[0].get());
+  ASSERT_THAT(array_el_ref, NotNull());
+  EXPECT_THAT(array_el_ref->value.dataType, Eq(android::Res_value::TYPE_INT_BOOLEAN));
+  EXPECT_THAT(array_el_ref->value.data, Eq(0xffffffffu));
+
+  auto actual_style = test::GetValue<Style>(apk->GetResourceTable(), "com.test:style/MyStyle");
+  ASSERT_THAT(actual_style, NotNull());
+  EXPECT_THAT(actual_style->entries.size(), Eq(2));
+
+  {
+    auto style_el = ValueCast<Reference>(actual_style->entries[0].value.get());
+    ASSERT_THAT(style_el, NotNull());
+    EXPECT_THAT(style_el->reference_type, Eq(Reference::Type::kAttribute));
+    EXPECT_THAT(style_el->id, Eq(0x7f010000));
+  }
+
+  {
+    auto style_el = ValueCast<String>(actual_style->entries[1].value.get());
+    ASSERT_THAT(style_el, NotNull());
+    EXPECT_THAT(*style_el->value, Eq("Hello World!"));
+  }
+
+  // Test substitution in compiled xml files
+  auto xml = apk->LoadXml("res/layout/layout.xml", &diag);
+  ASSERT_THAT(xml, NotNull());
+
+  auto& xml_attrs = xml->root->attributes;
+  ASSERT_THAT(xml_attrs.size(), Eq(2));
+
+  auto attr_value = ValueCast<Reference>(xml_attrs[0].compiled_value.get());
+  ASSERT_THAT(attr_value, NotNull());
+  EXPECT_THAT(attr_value->reference_type, Eq(Reference::Type::kResource));
+  EXPECT_THAT(attr_value->id, Eq(0x01060001));
+
+  EXPECT_THAT(xml_attrs[1].compiled_value.get(), IsNull());
+  EXPECT_THAT(xml_attrs[1].value, Eq("Hello World!"));
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/format/binary/TableFlattener.cpp b/tools/aapt2/format/binary/TableFlattener.cpp
index 17d11a63553a..74ecf47cae4c 100644
--- a/tools/aapt2/format/binary/TableFlattener.cpp
+++ b/tools/aapt2/format/binary/TableFlattener.cpp
@@ -567,13 +567,10 @@ class PackageFlattener {
   }
 
   bool FlattenTypes(BigBuffer* buffer) {
-    // Sort the types by their IDs. They will be inserted into the StringPool in
-    // this order.
-
     size_t expected_type_id = 1;
     for (const ResourceTableTypeView& type : package_.types) {
-      if (type.type == ResourceType::kStyleable) {
-        // Styleables aren't real Resource Types, they are represented in the R.java file.
+      if (type.type == ResourceType::kStyleable || type.type == ResourceType::kMacro) {
+        // Styleables and macros are not real resource types.
         continue;
       }
 
diff --git a/tools/aapt2/format/binary/XmlFlattener_test.cpp b/tools/aapt2/format/binary/XmlFlattener_test.cpp
index c24488b16153..d97e8882e5a2 100644
--- a/tools/aapt2/format/binary/XmlFlattener_test.cpp
+++ b/tools/aapt2/format/binary/XmlFlattener_test.cpp
@@ -222,7 +222,7 @@ TEST_F(XmlFlattenerTest, FlattenNonStandardPackageId) {
             android:id="@id/foo"
             app:foo="@id/foo" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   // The tree needs a custom DynamicRefTable since it is not using a standard app ID (0x7f).
diff --git a/tools/aapt2/format/proto/ProtoDeserialize.cpp b/tools/aapt2/format/proto/ProtoDeserialize.cpp
index 498d5a27d69d..ec331df480cd 100644
--- a/tools/aapt2/format/proto/ProtoDeserialize.cpp
+++ b/tools/aapt2/format/proto/ProtoDeserialize.cpp
@@ -656,6 +656,38 @@ static bool DeserializeReferenceFromPb(const pb::Reference& pb_ref, Reference* o
     }
     out_ref->name = name_ref.ToResourceName();
   }
+  if (pb_ref.type_flags() != 0) {
+    out_ref->type_flags = pb_ref.type_flags();
+  }
+  out_ref->allow_raw = pb_ref.allow_raw();
+  return true;
+}
+
+static bool DeserializeMacroFromPb(const pb::MacroBody& pb_ref, Macro* out_ref,
+                                   std::string* out_error) {
+  out_ref->raw_value = pb_ref.raw_string();
+
+  if (pb_ref.has_style_string()) {
+    out_ref->style_string.str = pb_ref.style_string().str();
+    for (const auto& span : pb_ref.style_string().spans()) {
+      out_ref->style_string.spans.emplace_back(Span{
+          .name = span.name(), .first_char = span.start_index(), .last_char = span.end_index()});
+    }
+  }
+
+  for (const auto& untranslatable_section : pb_ref.untranslatable_sections()) {
+    out_ref->untranslatable_sections.emplace_back(
+        UntranslatableSection{.start = static_cast<size_t>(untranslatable_section.start_index()),
+                              .end = static_cast<size_t>(untranslatable_section.end_index())});
+  }
+
+  for (const auto& namespace_decls : pb_ref.namespace_stack()) {
+    out_ref->alias_namespaces.emplace_back(
+        Macro::Namespace{.alias = namespace_decls.prefix(),
+                         .package_name = namespace_decls.package_name(),
+                         .is_private = namespace_decls.is_private()});
+  }
+
   return true;
 }
 
@@ -801,6 +833,15 @@ std::unique_ptr<Value> DeserializeValueFromPb(const pb::Value& pb_value,
         value = std::move(plural);
       } break;
 
+      case pb::CompoundValue::kMacro: {
+        const pb::MacroBody& pb_macro = pb_compound_value.macro();
+        auto macro = std::make_unique<Macro>();
+        if (!DeserializeMacroFromPb(pb_macro, macro.get(), out_error)) {
+          return {};
+        }
+        value = std::move(macro);
+      } break;
+
       default:
         LOG(FATAL) << "unknown compound value: " << (int)pb_compound_value.value_case();
         break;
diff --git a/tools/aapt2/format/proto/ProtoSerialize.cpp b/tools/aapt2/format/proto/ProtoSerialize.cpp
index f13f82da3102..d2f033683cc5 100644
--- a/tools/aapt2/format/proto/ProtoSerialize.cpp
+++ b/tools/aapt2/format/proto/ProtoSerialize.cpp
@@ -440,6 +440,36 @@ static void SerializeReferenceToPb(const Reference& ref, pb::Reference* pb_ref)
   if (ref.is_dynamic) {
     pb_ref->mutable_is_dynamic()->set_value(ref.is_dynamic);
   }
+  if (ref.type_flags) {
+    pb_ref->set_type_flags(*ref.type_flags);
+  }
+  pb_ref->set_allow_raw(ref.allow_raw);
+}
+
+static void SerializeMacroToPb(const Macro& ref, pb::MacroBody* pb_macro) {
+  pb_macro->set_raw_string(ref.raw_value);
+
+  auto pb_style_str = pb_macro->mutable_style_string();
+  pb_style_str->set_str(ref.style_string.str);
+  for (const auto& span : ref.style_string.spans) {
+    auto pb_span = pb_style_str->add_spans();
+    pb_span->set_name(span.name);
+    pb_span->set_start_index(span.first_char);
+    pb_span->set_end_index(span.last_char);
+  }
+
+  for (const auto& untranslatable_section : ref.untranslatable_sections) {
+    auto pb_section = pb_macro->add_untranslatable_sections();
+    pb_section->set_start_index(untranslatable_section.start);
+    pb_section->set_end_index(untranslatable_section.end);
+  }
+
+  for (const auto& namespace_decls : ref.alias_namespaces) {
+    auto pb_namespace = pb_macro->add_namespace_stack();
+    pb_namespace->set_prefix(namespace_decls.alias);
+    pb_namespace->set_package_name(namespace_decls.package_name);
+    pb_namespace->set_is_private(namespace_decls.is_private);
+  }
 }
 
 template <typename T>
@@ -643,6 +673,11 @@ class ValueSerializer : public ConstValueVisitor {
     }
   }
 
+  void Visit(const Macro* macro) override {
+    pb::MacroBody* pb_macro = out_value_->mutable_compound_value()->mutable_macro();
+    SerializeMacroToPb(*macro, pb_macro);
+  }
+
   void VisitAny(const Value* unknown) override {
     LOG(FATAL) << "unimplemented value: " << *unknown;
   }
diff --git a/tools/aapt2/format/proto/ProtoSerialize_test.cpp b/tools/aapt2/format/proto/ProtoSerialize_test.cpp
index 591ba14942cd..e563eda93e20 100644
--- a/tools/aapt2/format/proto/ProtoSerialize_test.cpp
+++ b/tools/aapt2/format/proto/ProtoSerialize_test.cpp
@@ -894,4 +894,38 @@ TEST(ProtoSerializeTest, ObfuscatingResourceNamesWithNameCollapseExemptionsSucce
   EXPECT_THAT(*(s->value), Eq("foo"));
 }
 
+TEST(ProtoSerializeTest, SerializeMacro) {
+  auto original = std::make_unique<Macro>();
+  original->raw_value = "\nThis being human is a guest house.";
+  original->style_string.str = " This being human is a guest house.";
+  original->style_string.spans.emplace_back(Span{.name = "b", .first_char = 12, .last_char = 16});
+  original->untranslatable_sections.emplace_back(UntranslatableSection{.start = 12, .end = 17});
+  original->alias_namespaces.emplace_back(
+      Macro::Namespace{.alias = "prefix", .package_name = "package.name", .is_private = true});
+
+  CloningValueTransformer cloner(nullptr);
+  std::unique_ptr<IAaptContext> context = test::ContextBuilder().Build();
+  std::unique_ptr<ResourceTable> table = test::ResourceTableBuilder()
+                                             .Add(NewResourceBuilder("com.app.a:macro/foo")
+                                                      .SetValue(original->Transform(cloner))
+                                                      .Build())
+                                             .Build();
+
+  ResourceTable new_table;
+  pb::ResourceTable pb_table;
+  MockFileCollection files;
+  std::string error;
+  SerializeTableToPb(*table, &pb_table, context->GetDiagnostics());
+  ASSERT_TRUE(DeserializeTableFromPb(pb_table, &files, &new_table, &error));
+  EXPECT_THAT(error, IsEmpty());
+
+  Macro* deserialized = test::GetValue<Macro>(&new_table, "com.app.a:macro/foo");
+  ASSERT_THAT(deserialized, NotNull());
+  EXPECT_THAT(deserialized->raw_value, Eq(original->raw_value));
+  EXPECT_THAT(deserialized->style_string.str, Eq(original->style_string.str));
+  EXPECT_THAT(deserialized->style_string.spans, Eq(original->style_string.spans));
+  EXPECT_THAT(deserialized->untranslatable_sections, Eq(original->untranslatable_sections));
+  EXPECT_THAT(deserialized->alias_namespaces, Eq(original->alias_namespaces));
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/java/JavaClassGenerator.cpp b/tools/aapt2/java/JavaClassGenerator.cpp
index e1e2e0135cf7..de6524dc7027 100644
--- a/tools/aapt2/java/JavaClassGenerator.cpp
+++ b/tools/aapt2/java/JavaClassGenerator.cpp
@@ -616,8 +616,9 @@ bool JavaClassGenerator::Generate(const StringPiece& package_name_to_generate,
 
   for (const auto& package : table_->packages) {
     for (const auto& type : package->types) {
-      if (type->type == ResourceType::kAttrPrivate) {
-        // We generate these as part of the kAttr type, so skip them here.
+      if (type->type == ResourceType::kAttrPrivate || type->type == ResourceType::kMacro) {
+        // We generate kAttrPrivate as part of the kAttr type, so skip them here.
+        // Macros are not actual resources, so skip them as well.
         continue;
       }
 
diff --git a/tools/aapt2/java/JavaClassGenerator_test.cpp b/tools/aapt2/java/JavaClassGenerator_test.cpp
index d08b61e5ff66..40395ed64fe3 100644
--- a/tools/aapt2/java/JavaClassGenerator_test.cpp
+++ b/tools/aapt2/java/JavaClassGenerator_test.cpp
@@ -570,4 +570,25 @@ TEST(JavaClassGeneratorTest, SortsDynamicAttributesAfterFrameworkAttributes) {
   EXPECT_THAT(output, HasSubstr("public static final int MyStyleable_dynamic_attr=1;"));
 }
 
+TEST(JavaClassGeneratorTest, SkipMacros) {
+  std::unique_ptr<ResourceTable> table =
+      test::ResourceTableBuilder()
+          .AddValue("android:macro/bar", ResourceId(0x01010000), test::AttributeBuilder().Build())
+          .Build();
+
+  std::unique_ptr<IAaptContext> context =
+      test::ContextBuilder()
+          .AddSymbolSource(util::make_unique<ResourceTableSymbolSource>(table.get()))
+          .SetNameManglerPolicy(NameManglerPolicy{"android"})
+          .Build();
+  JavaClassGenerator generator(context.get(), table.get(), {});
+
+  std::string output;
+  StringOutputStream out(&output);
+  EXPECT_TRUE(generator.Generate("android", &out));
+  out.Flush();
+
+  EXPECT_THAT(output, Not(HasSubstr("bar")));
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/java/ProguardRules_test.cpp b/tools/aapt2/java/ProguardRules_test.cpp
index b7dfec3a6b28..e1040666e410 100644
--- a/tools/aapt2/java/ProguardRules_test.cpp
+++ b/tools/aapt2/java/ProguardRules_test.cpp
@@ -264,7 +264,7 @@ TEST(ProguardRulesTest, IncludedLayoutRulesAreConditional) {
       </View>)");
   foo_layout->file.name = test::ParseNameOrDie("com.foo:layout/foo");
 
-  XmlReferenceLinker xml_linker;
+  XmlReferenceLinker xml_linker(nullptr);
   ASSERT_TRUE(xml_linker.Consume(context.get(), bar_layout.get()));
   ASSERT_TRUE(xml_linker.Consume(context.get(), foo_layout.get()));
 
diff --git a/tools/aapt2/link/Linkers.h b/tools/aapt2/link/Linkers.h
index c9b8d3993959..be6c930b9284 100644
--- a/tools/aapt2/link/Linkers.h
+++ b/tools/aapt2/link/Linkers.h
@@ -133,12 +133,14 @@ class XmlNamespaceRemover : public IXmlResourceConsumer {
 // Once an XmlResource is processed by this linker, it is ready to be flattened.
 class XmlReferenceLinker : public IXmlResourceConsumer {
  public:
-  XmlReferenceLinker() = default;
+  explicit XmlReferenceLinker(ResourceTable* table) : table_(table) {
+  }
 
   bool Consume(IAaptContext* context, xml::XmlResource* resource) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(XmlReferenceLinker);
+  ResourceTable* table_;
 };
 
 }  // namespace aapt
diff --git a/tools/aapt2/link/ReferenceLinker.cpp b/tools/aapt2/link/ReferenceLinker.cpp
index 8e49fabe6a5c..4ac25bd6a0e0 100644
--- a/tools/aapt2/link/ReferenceLinker.cpp
+++ b/tools/aapt2/link/ReferenceLinker.cpp
@@ -21,6 +21,7 @@
 #include "androidfw/ResourceTypes.h"
 
 #include "Diagnostics.h"
+#include "ResourceParser.h"
 #include "ResourceTable.h"
 #include "ResourceUtils.h"
 #include "ResourceValues.h"
@@ -37,128 +38,153 @@ using ::android::StringPiece;
 using ::android::base::StringPrintf;
 
 namespace aapt {
-
 namespace {
+struct LoggingResourceName {
+  LoggingResourceName(const Reference& ref, const CallSite& callsite,
+                      const xml::IPackageDeclStack* decls)
+      : ref_(ref), callsite_(callsite), decls_(decls) {
+  }
 
-// The ReferenceLinkerVisitor will follow all references and make sure they point
-// to resources that actually exist, either in the local resource table, or as external
-// symbols. Once the target resource has been found, the ID of the resource will be assigned
-// to the reference object.
-//
-// NOTE: All of the entries in the ResourceTable must be assigned IDs.
-class ReferenceLinkerVisitor : public DescendingValueVisitor {
- public:
-  using DescendingValueVisitor::Visit;
-
-  ReferenceLinkerVisitor(const CallSite& callsite, IAaptContext* context, SymbolTable* symbols,
-                         StringPool* string_pool, xml::IPackageDeclStack* decl)
-      : callsite_(callsite),
-        context_(context),
-        symbols_(symbols),
-        package_decls_(decl),
-        string_pool_(string_pool) {}
-
-  void Visit(Reference* ref) override {
-    if (!ReferenceLinker::LinkReference(callsite_, ref, context_, symbols_, package_decls_)) {
-      error_ = true;
-    }
+  const Reference& ref_;
+  const CallSite& callsite_;
+  const xml::IPackageDeclStack* decls_;
+};
+
+inline ::std::ostream& operator<<(::std::ostream& out, const LoggingResourceName& name) {
+  if (!name.ref_.name) {
+    out << name.ref_.id.value();
+    return out;
   }
 
-  // We visit the Style specially because during this phase, values of attributes are
-  // all RawString values. Now that we are expected to resolve all symbols, we can
-  // lookup the attributes to find out which types are allowed for the attributes' values.
-  void Visit(Style* style) override {
-    if (style->parent) {
-      Visit(&style->parent.value());
-    }
+  out << name.ref_.name.value();
+
+  Reference fully_qualified = name.ref_;
+  xml::ResolvePackage(name.decls_, &fully_qualified);
+
+  ResourceName& full_name = fully_qualified.name.value();
+  if (full_name.package.empty()) {
+    full_name.package = name.callsite_.package;
+  }
 
-    for (Style::Entry& entry : style->entries) {
-      std::string err_str;
+  if (full_name != name.ref_.name.value()) {
+    out << " (aka " << full_name << ")";
+  }
+  return out;
+}
 
-      // Transform the attribute reference so that it is using the fully qualified package
-      // name. This will also mark the reference as being able to see private resources if
-      // there was a '*' in the reference or if the package came from the private namespace.
-      Reference transformed_reference = entry.key;
-      ResolvePackage(package_decls_, &transformed_reference);
+}  // namespace
 
-      // Find the attribute in the symbol table and check if it is visible from this callsite.
-      const SymbolTable::Symbol* symbol = ReferenceLinker::ResolveAttributeCheckVisibility(
-          transformed_reference, callsite_, context_, symbols_, &err_str);
-      if (symbol) {
-        // Assign our style key the correct ID. The ID may not exist.
-        entry.key.id = symbol->id;
-
-        // Try to convert the value to a more specific, typed value based on the attribute it is
-        // set to.
-        entry.value = ParseValueWithAttribute(std::move(entry.value), symbol->attribute.get());
-
-        // Link/resolve the final value (mostly if it's a reference).
-        entry.value->Accept(this);
-
-        // Now verify that the type of this item is compatible with the
-        // attribute it is defined for. We pass `nullptr` as the DiagMessage so that this
-        // check is fast and we avoid creating a DiagMessage when the match is successful.
-        if (!symbol->attribute->Matches(*entry.value, nullptr)) {
-          // The actual type of this item is incompatible with the attribute.
-          DiagMessage msg(entry.key.GetSource());
-
-          // Call the matches method again, this time with a DiagMessage so we fill in the actual
-          // error message.
-          symbol->attribute->Matches(*entry.value, &msg);
-          context_->GetDiagnostics()->Error(msg);
-          error_ = true;
-        }
+std::unique_ptr<Reference> ReferenceLinkerTransformer::TransformDerived(const Reference* value) {
+  auto linked_item =
+      ReferenceLinker::LinkReference(callsite_, *value, context_, symbols_, table_, package_decls_);
+  if (linked_item) {
+    auto linked_item_ptr = linked_item.release();
+    if (auto ref = ValueCast<Reference>(linked_item_ptr)) {
+      return std::unique_ptr<Reference>(ref);
+    }
+    context_->GetDiagnostics()->Error(DiagMessage(value->GetSource())
+                                      << "value of '"
+                                      << LoggingResourceName(*value, callsite_, package_decls_)
+                                      << "' must be a resource reference");
+    delete linked_item_ptr;
+  }
+
+  error_ = true;
+  return CloningValueTransformer::TransformDerived(value);
+}
+
+std::unique_ptr<Style> ReferenceLinkerTransformer::TransformDerived(const Style* style) {
+  // We visit the Style specially because during this phase, values of attributes are either
+  // RawString or Reference values. Now that we are expected to resolve all symbols, we can lookup
+  // the attributes to find out which types are allowed for the attributes' values.
+  auto new_style = CloningValueTransformer::TransformDerived(style);
+  if (new_style->parent) {
+    new_style->parent = *TransformDerived(&style->parent.value());
+  }
 
-      } else {
+  for (Style::Entry& entry : new_style->entries) {
+    std::string err_str;
+
+    // Transform the attribute reference so that it is using the fully qualified package
+    // name. This will also mark the reference as being able to see private resources if
+    // there was a '*' in the reference or if the package came from the private namespace.
+    Reference transformed_reference = entry.key;
+    ResolvePackage(package_decls_, &transformed_reference);
+
+    // Find the attribute in the symbol table and check if it is visible from this callsite.
+    const SymbolTable::Symbol* symbol = ReferenceLinker::ResolveAttributeCheckVisibility(
+        transformed_reference, callsite_, context_, symbols_, &err_str);
+    if (symbol) {
+      // Assign our style key the correct ID. The ID may not exist.
+      entry.key.id = symbol->id;
+
+      // Link/resolve the final value if it's a reference.
+      entry.value = entry.value->Transform(*this);
+
+      // Try to convert the value to a more specific, typed value based on the attribute it is
+      // set to.
+      entry.value = ParseValueWithAttribute(std::move(entry.value), symbol->attribute.get());
+
+      // Now verify that the type of this item is compatible with the
+      // attribute it is defined for. We pass `nullptr` as the DiagMessage so that this
+      // check is fast and we avoid creating a DiagMessage when the match is successful.
+      if (!symbol->attribute->Matches(*entry.value, nullptr)) {
+        // The actual type of this item is incompatible with the attribute.
         DiagMessage msg(entry.key.GetSource());
-        msg << "style attribute '";
-        ReferenceLinker::WriteResourceName(entry.key, callsite_, package_decls_, &msg);
-        msg << "' " << err_str;
+
+        // Call the matches method again, this time with a DiagMessage so we fill in the actual
+        // error message.
+        symbol->attribute->Matches(*entry.value, &msg);
         context_->GetDiagnostics()->Error(msg);
         error_ = true;
       }
+    } else {
+      context_->GetDiagnostics()->Error(DiagMessage(entry.key.GetSource())
+                                        << "style attribute '"
+                                        << LoggingResourceName(entry.key, callsite_, package_decls_)
+                                        << "' " << err_str);
+
+      error_ = true;
     }
   }
+  return new_style;
+}
 
-  bool HasError() {
-    return error_;
+std::unique_ptr<Item> ReferenceLinkerTransformer::TransformItem(const Reference* value) {
+  auto linked_value =
+      ReferenceLinker::LinkReference(callsite_, *value, context_, symbols_, table_, package_decls_);
+  if (linked_value) {
+    return linked_value;
   }
+  error_ = true;
+  return CloningValueTransformer::TransformDerived(value);
+}
 
- private:
-  DISALLOW_COPY_AND_ASSIGN(ReferenceLinkerVisitor);
-
-  // Transform a RawString value into a more specific, appropriate value, based on the
-  // Attribute. If a non RawString value is passed in, this is an identity transform.
-  std::unique_ptr<Item> ParseValueWithAttribute(std::unique_ptr<Item> value,
-                                                const Attribute* attr) {
-    if (RawString* raw_string = ValueCast<RawString>(value.get())) {
-      std::unique_ptr<Item> transformed =
-          ResourceUtils::TryParseItemForAttribute(*raw_string->value, attr);
-
-      // If we could not parse as any specific type, try a basic STRING.
-      if (!transformed && (attr->type_mask & android::ResTable_map::TYPE_STRING)) {
-        StringBuilder string_builder;
-        string_builder.AppendText(*raw_string->value);
-        if (string_builder) {
-          transformed =
-              util::make_unique<String>(string_pool_->MakeRef(string_builder.to_string()));
-        }
+// Transform a RawString value into a more specific, appropriate value, based on the
+// Attribute. If a non RawString value is passed in, this is an identity transform.
+std::unique_ptr<Item> ReferenceLinkerTransformer::ParseValueWithAttribute(
+    std::unique_ptr<Item> value, const Attribute* attr) {
+  if (RawString* raw_string = ValueCast<RawString>(value.get())) {
+    std::unique_ptr<Item> transformed =
+        ResourceUtils::TryParseItemForAttribute(*raw_string->value, attr);
+
+    // If we could not parse as any specific type, try a basic STRING.
+    if (!transformed && (attr->type_mask & android::ResTable_map::TYPE_STRING)) {
+      StringBuilder string_builder;
+      string_builder.AppendText(*raw_string->value);
+      if (string_builder) {
+        transformed = util::make_unique<String>(pool_->MakeRef(string_builder.to_string()));
       }
+    }
 
-      if (transformed) {
-        return transformed;
-      }
+    if (transformed) {
+      return transformed;
     }
-    return value;
   }
+  return value;
+}
 
-  const CallSite& callsite_;
-  IAaptContext* context_;
-  SymbolTable* symbols_;
-  xml::IPackageDeclStack* package_decls_;
-  StringPool* string_pool_;
-  bool error_ = false;
-};
+namespace {
 
 class EmptyDeclStack : public xml::IPackageDeclStack {
  public:
@@ -175,6 +201,27 @@ class EmptyDeclStack : public xml::IPackageDeclStack {
   DISALLOW_COPY_AND_ASSIGN(EmptyDeclStack);
 };
 
+struct MacroDeclStack : public xml::IPackageDeclStack {
+  explicit MacroDeclStack(std::vector<Macro::Namespace> namespaces)
+      : alias_namespaces_(std::move(namespaces)) {
+  }
+
+  Maybe<xml::ExtractedPackage> TransformPackageAlias(const StringPiece& alias) const override {
+    if (alias.empty()) {
+      return xml::ExtractedPackage{{}, true /*private*/};
+    }
+    for (auto it = alias_namespaces_.rbegin(); it != alias_namespaces_.rend(); ++it) {
+      if (alias == StringPiece(it->alias)) {
+        return xml::ExtractedPackage{it->package_name, it->is_private};
+      }
+    }
+    return {};
+  }
+
+ private:
+  std::vector<Macro::Namespace> alias_namespaces_;
+};
+
 // The symbol is visible if it is public, or if the reference to it is requesting private access
 // or if the callsite comes from the same package.
 bool IsSymbolVisible(const SymbolTable::Symbol& symbol, const Reference& ref,
@@ -220,8 +267,6 @@ const SymbolTable::Symbol* ReferenceLinker::ResolveSymbol(const Reference& refer
       // If the callsite package is the same as the current compilation package,
       // check the feature split dependencies as well. Feature split resources
       // can be referenced without a namespace, just like the base package.
-      // TODO: modify the package name of included splits instead of having the
-      // symbol table look up the resource in in every package. b/136105066
       if (callsite.package == context->GetCompilationPackage()) {
         const auto& split_name_dependencies = context->GetSplitNameDependencies();
         for (const std::string& split_name : split_name_dependencies) {
@@ -295,29 +340,6 @@ Maybe<xml::AaptAttribute> ReferenceLinker::CompileXmlAttribute(const Reference&
   return xml::AaptAttribute(*symbol->attribute, symbol->id);
 }
 
-void ReferenceLinker::WriteResourceName(const Reference& ref, const CallSite& callsite,
-                                        const xml::IPackageDeclStack* decls, DiagMessage* out_msg) {
-  CHECK(out_msg != nullptr);
-  if (!ref.name) {
-    *out_msg << ref.id.value();
-    return;
-  }
-
-  *out_msg << ref.name.value();
-
-  Reference fully_qualified = ref;
-  xml::ResolvePackage(decls, &fully_qualified);
-
-  ResourceName& full_name = fully_qualified.name.value();
-  if (full_name.package.empty()) {
-    full_name.package = callsite.package;
-  }
-
-  if (full_name != ref.name.value()) {
-    *out_msg << " (aka " << full_name << ")";
-  }
-}
-
 void ReferenceLinker::WriteAttributeName(const Reference& ref, const CallSite& callsite,
                                          const xml::IPackageDeclStack* decls,
                                          DiagMessage* out_msg) {
@@ -348,18 +370,71 @@ void ReferenceLinker::WriteAttributeName(const Reference& ref, const CallSite& c
   }
 }
 
-bool ReferenceLinker::LinkReference(const CallSite& callsite, Reference* reference,
-                                    IAaptContext* context, SymbolTable* symbols,
-                                    const xml::IPackageDeclStack* decls) {
-  CHECK(reference != nullptr);
-  if (!reference->name && !reference->id) {
+std::unique_ptr<Item> ReferenceLinker::LinkReference(const CallSite& callsite,
+                                                     const Reference& reference,
+                                                     IAaptContext* context, SymbolTable* symbols,
+                                                     ResourceTable* table,
+                                                     const xml::IPackageDeclStack* decls) {
+  if (!reference.name && !reference.id) {
     // This is @null.
-    return true;
+    return std::make_unique<Reference>(reference);
   }
 
-  Reference transformed_reference = *reference;
+  Reference transformed_reference = reference;
   xml::ResolvePackage(decls, &transformed_reference);
 
+  if (transformed_reference.name.value().type == ResourceType::kMacro) {
+    if (transformed_reference.name.value().package.empty()) {
+      transformed_reference.name.value().package = callsite.package;
+    }
+
+    auto result = table->FindResource(transformed_reference.name.value());
+    if (!result || result.value().entry->values.empty()) {
+      context->GetDiagnostics()->Error(
+          DiagMessage(reference.GetSource())
+          << "failed to find definition for "
+          << LoggingResourceName(transformed_reference, callsite, decls));
+      return {};
+    }
+
+    auto& macro_values = result.value().entry->values;
+    CHECK(macro_values.size() == 1) << "Macros can only be defined in the default configuration.";
+
+    auto macro = ValueCast<Macro>(macro_values[0]->value.get());
+    CHECK(macro != nullptr) << "Value of macro resource is not a Macro (actual "
+                            << *macro_values[0]->value << ")";
+
+    // Re-create the state used to parse the macro tag to compile the macro contents as if it was
+    // defined inline
+    uint32_t type_flags = 0;
+    if (reference.type_flags.has_value()) {
+      type_flags = reference.type_flags.value();
+    }
+
+    MacroDeclStack namespace_stack(macro->alias_namespaces);
+    FlattenedXmlSubTree sub_tree{.raw_value = macro->raw_value,
+                                 .style_string = macro->style_string,
+                                 .untranslatable_sections = macro->untranslatable_sections,
+                                 .namespace_resolver = &namespace_stack,
+                                 .source = macro->GetSource()};
+
+    auto new_value = ResourceParser::ParseXml(sub_tree, type_flags, reference.allow_raw, *table,
+                                              macro_values[0]->config, *context->GetDiagnostics());
+    if (new_value == nullptr) {
+      context->GetDiagnostics()->Error(
+          DiagMessage(reference.GetSource())
+          << "failed to substitute macro "
+          << LoggingResourceName(transformed_reference, callsite, decls)
+          << ": failed to parse contents as one of type(s) " << Attribute::MaskString(type_flags));
+      return {};
+    }
+
+    if (auto ref = ValueCast<Reference>(new_value.get())) {
+      return LinkReference(callsite, *ref, context, symbols, table, decls);
+    }
+    return new_value;
+  }
+
   std::string err_str;
   const SymbolTable::Symbol* s =
       ResolveSymbolCheckVisibility(transformed_reference, callsite, context, symbols, &err_str);
@@ -367,17 +442,17 @@ bool ReferenceLinker::LinkReference(const CallSite& callsite, Reference* referen
     // The ID may not exist. This is fine because of the possibility of building
     // against libraries without assigned IDs.
     // Ex: Linking against own resources when building a static library.
-    reference->id = s->id;
-    reference->is_dynamic = s->is_dynamic;
-    return true;
+    auto new_ref = std::make_unique<Reference>(reference);
+    new_ref->id = s->id;
+    new_ref->is_dynamic = s->is_dynamic;
+    return std::move(new_ref);
   }
 
-  DiagMessage error_msg(reference->GetSource());
-  error_msg << "resource ";
-  WriteResourceName(*reference, callsite, decls, &error_msg);
-  error_msg << " " << err_str;
-  context->GetDiagnostics()->Error(error_msg);
-  return false;
+  context->GetDiagnostics()->Error(DiagMessage(reference.GetSource())
+                                   << "resource "
+                                   << LoggingResourceName(transformed_reference, callsite, decls)
+                                   << " " << err_str);
+  return {};
 }
 
 bool ReferenceLinker::Consume(IAaptContext* context, ResourceTable* table) {
@@ -412,14 +487,15 @@ bool ReferenceLinker::Consume(IAaptContext* context, ResourceTable* table) {
 
         // The context of this resource is the package in which it is defined.
         const CallSite callsite{name.package};
-        ReferenceLinkerVisitor visitor(callsite, context, context->GetExternalSymbols(),
-                                       &table->string_pool, &decl_stack);
+        ReferenceLinkerTransformer reference_transformer(callsite, context,
+                                                         context->GetExternalSymbols(),
+                                                         &table->string_pool, table, &decl_stack);
 
         for (auto& config_value : entry->values) {
-          config_value->value->Accept(&visitor);
+          config_value->value = config_value->value->Transform(reference_transformer);
         }
 
-        if (visitor.HasError()) {
+        if (reference_transformer.HasError()) {
           error = true;
         }
       }
diff --git a/tools/aapt2/link/ReferenceLinker.h b/tools/aapt2/link/ReferenceLinker.h
index 1256709edbf4..770f1e500ac0 100644
--- a/tools/aapt2/link/ReferenceLinker.h
+++ b/tools/aapt2/link/ReferenceLinker.h
@@ -28,6 +28,41 @@
 
 namespace aapt {
 
+// A ValueTransformer that returns fully linked versions of resource and macro references.
+class ReferenceLinkerTransformer : public CloningValueTransformer {
+ public:
+  ReferenceLinkerTransformer(const CallSite& callsite, IAaptContext* context, SymbolTable* symbols,
+                             StringPool* string_pool, ResourceTable* table,
+                             xml::IPackageDeclStack* decl)
+      : CloningValueTransformer(string_pool),
+        callsite_(callsite),
+        context_(context),
+        symbols_(symbols),
+        table_(table),
+        package_decls_(decl) {
+  }
+
+  std::unique_ptr<Reference> TransformDerived(const Reference* value) override;
+  std::unique_ptr<Item> TransformItem(const Reference* value) override;
+  std::unique_ptr<Style> TransformDerived(const Style* value) override;
+
+  bool HasError() {
+    return error_;
+  }
+
+ private:
+  // Transform a RawString value into a more specific, appropriate value, based on the
+  // Attribute. If a non RawString value is passed in, this is an identity transform.
+  std::unique_ptr<Item> ParseValueWithAttribute(std::unique_ptr<Item> value, const Attribute* attr);
+
+  const CallSite& callsite_;
+  IAaptContext* context_;
+  SymbolTable* symbols_;
+  ResourceTable* table_;
+  xml::IPackageDeclStack* package_decls_;
+  bool error_ = false;
+};
+
 // Resolves all references to resources in the ResourceTable and assigns them IDs.
 // The ResourceTable must already have IDs assigned to each resource.
 // Once the ResourceTable is processed by this linker, it is ready to be flattened.
@@ -70,19 +105,28 @@ class ReferenceLinker : public IResourceTableConsumer {
 
   // Writes the resource name to the DiagMessage, using the
   // "orig_name (aka <transformed_name>)" syntax.
-  static void WriteResourceName(const Reference& orig, const CallSite& callsite,
-                                const xml::IPackageDeclStack* decls, DiagMessage* out_msg);
+  /*static void WriteResourceName(const Reference& orig, const CallSite& callsite,
+                                const xml::IPackageDeclStack* decls, DiagMessage* out_msg);*/
 
   // Same as WriteResourceName but omits the 'attr' part.
   static void WriteAttributeName(const Reference& ref, const CallSite& callsite,
                                  const xml::IPackageDeclStack* decls, DiagMessage* out_msg);
 
-  // Transforms the package name of the reference to the fully qualified package name using
-  // the xml::IPackageDeclStack, then mangles and looks up the symbol. If the symbol is visible
-  // to the reference at the callsite, the reference is updated with an ID.
-  // Returns false on failure, and an error message is logged to the IDiagnostics in the context.
-  static bool LinkReference(const CallSite& callsite, Reference* reference, IAaptContext* context,
-                            SymbolTable* symbols, const xml::IPackageDeclStack* decls);
+  // Returns a fully linked version a resource reference.
+  //
+  // If the reference points to a non-macro resource, the xml::IPackageDeclStack is used to
+  // determine the fully qualified name of the referenced resource. If the symbol is visible
+  // to the reference at the callsite, a copy of the reference with an updated updated ID is
+  // returned.
+  //
+  // If the reference points to a macro, the ResourceTable is used to find the macro definition and
+  // substitute its contents in place of the reference.
+  //
+  // Returns nullptr on failure, and an error message is logged to the IDiagnostics in the context.
+  static std::unique_ptr<Item> LinkReference(const CallSite& callsite, const Reference& reference,
+                                             IAaptContext* context, SymbolTable* symbols,
+                                             ResourceTable* table,
+                                             const xml::IPackageDeclStack* decls);
 
   // Links all references in the ResourceTable.
   bool Consume(IAaptContext* context, ResourceTable* table) override;
diff --git a/tools/aapt2/link/ReferenceLinker_test.cpp b/tools/aapt2/link/ReferenceLinker_test.cpp
index 228c5bd743a0..2d8f0d39053f 100644
--- a/tools/aapt2/link/ReferenceLinker_test.cpp
+++ b/tools/aapt2/link/ReferenceLinker_test.cpp
@@ -365,4 +365,22 @@ TEST(ReferenceLinkerTest, ReferenceSymbolFromOtherSplit) {
   EXPECT_THAT(s, IsNull());
 }
 
+TEST(ReferenceLinkerTest, MacroFailToFindDefinition) {
+  std::unique_ptr<ResourceTable> table =
+      test::ResourceTableBuilder()
+          .AddReference("com.app.test:string/foo", ResourceId(0x7f020000), "com.app.test:macro/bar")
+          .Build();
+
+  std::unique_ptr<IAaptContext> context =
+      test::ContextBuilder()
+          .SetCompilationPackage("com.app.test")
+          .SetPackageId(0x7f)
+          .SetNameManglerPolicy(NameManglerPolicy{"com.app.test"})
+          .AddSymbolSource(util::make_unique<ResourceTableSymbolSource>(table.get()))
+          .Build();
+
+  ReferenceLinker linker;
+  ASSERT_FALSE(linker.Consume(context.get(), table.get()));
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/link/XmlCompatVersioner_test.cpp b/tools/aapt2/link/XmlCompatVersioner_test.cpp
index a98ab0f76de4..d63809615a5b 100644
--- a/tools/aapt2/link/XmlCompatVersioner_test.cpp
+++ b/tools/aapt2/link/XmlCompatVersioner_test.cpp
@@ -82,7 +82,7 @@ TEST_F(XmlCompatVersionerTest, NoRulesOnlyStripsAndCopies) {
           app:foo="16dp"
           foo="bar"/>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   XmlCompatVersioner::Rules rules;
@@ -121,7 +121,7 @@ TEST_F(XmlCompatVersionerTest, SingleRule) {
           app:foo="16dp"
           foo="bar"/>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   XmlCompatVersioner::Rules rules;
@@ -181,7 +181,7 @@ TEST_F(XmlCompatVersionerTest, ChainedRule) {
       <View xmlns:android="http://schemas.android.com/apk/res/android"
           android:paddingHorizontal="24dp" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   XmlCompatVersioner::Rules rules;
@@ -256,7 +256,7 @@ TEST_F(XmlCompatVersionerTest, DegradeRuleOverridesExistingAttribute) {
           android:paddingLeft="16dp"
           android:paddingRight="16dp"/>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   Item* padding_horizontal_value =
diff --git a/tools/aapt2/link/XmlReferenceLinker.cpp b/tools/aapt2/link/XmlReferenceLinker.cpp
index c3c16b92f712..aaa085e2eb15 100644
--- a/tools/aapt2/link/XmlReferenceLinker.cpp
+++ b/tools/aapt2/link/XmlReferenceLinker.cpp
@@ -33,49 +33,18 @@ namespace aapt {
 
 namespace {
 
-// Visits all references (including parents of styles, references in styles, arrays, etc) and
-// links their symbolic name to their Resource ID, performing mangling and package aliasing
-// as needed.
-class ReferenceVisitor : public DescendingValueVisitor {
- public:
-  using DescendingValueVisitor::Visit;
-
-  ReferenceVisitor(const CallSite& callsite, IAaptContext* context, SymbolTable* symbols,
-                   xml::IPackageDeclStack* decls)
-      : callsite_(callsite), context_(context), symbols_(symbols), decls_(decls), error_(false) {}
-
-  void Visit(Reference* ref) override {
-    if (!ReferenceLinker::LinkReference(callsite_, ref, context_, symbols_, decls_)) {
-      error_ = true;
-    }
-  }
-
-  bool HasError() const {
-    return error_;
-  }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ReferenceVisitor);
-
-  const CallSite& callsite_;
-  IAaptContext* context_;
-  SymbolTable* symbols_;
-  xml::IPackageDeclStack* decls_;
-  bool error_;
-};
-
 // Visits each xml Element and compiles the attributes within.
 class XmlVisitor : public xml::PackageAwareVisitor {
  public:
   using xml::PackageAwareVisitor::Visit;
 
-  XmlVisitor(const Source& source, const CallSite& callsite, IAaptContext* context,
-             SymbolTable* symbols)
+  XmlVisitor(const Source& source, StringPool* pool, const CallSite& callsite,
+             IAaptContext* context, ResourceTable* table, SymbolTable* symbols)
       : source_(source),
         callsite_(callsite),
         context_(context),
         symbols_(symbols),
-        reference_visitor_(callsite, context, symbols, this) {
+        reference_transformer_(callsite, context, symbols, pool, table, this) {
   }
 
   void Visit(xml::Element* el) override {
@@ -127,7 +96,7 @@ class XmlVisitor : public xml::PackageAwareVisitor {
       if (attr.compiled_value) {
         // With a compiledValue, we must resolve the reference and assign it an ID.
         attr.compiled_value->SetSource(source);
-        attr.compiled_value->Accept(&reference_visitor_);
+        attr.compiled_value = attr.compiled_value->Transform(reference_transformer_);
       } else if ((attribute->type_mask & android::ResTable_map::TYPE_STRING) == 0) {
         // We won't be able to encode this as a string.
         DiagMessage msg(source);
@@ -143,7 +112,7 @@ class XmlVisitor : public xml::PackageAwareVisitor {
   }
 
   bool HasError() {
-    return error_ || reference_visitor_.HasError();
+    return error_ || reference_transformer_.HasError();
   }
 
  private:
@@ -154,7 +123,7 @@ class XmlVisitor : public xml::PackageAwareVisitor {
   IAaptContext* context_;
   SymbolTable* symbols_;
 
-  ReferenceVisitor reference_visitor_;
+  ReferenceLinkerTransformer reference_transformer_;
   bool error_ = false;
 };
 
@@ -173,7 +142,8 @@ bool XmlReferenceLinker::Consume(IAaptContext* context, xml::XmlResource* resour
     callsite.package = context->GetCompilationPackage();
   }
 
-  XmlVisitor visitor(resource->file.source, callsite, context, context->GetExternalSymbols());
+  XmlVisitor visitor(resource->file.source, &resource->string_pool, callsite, context, table_,
+                     context->GetExternalSymbols());
   if (resource->root) {
     resource->root->Accept(&visitor);
     return !visitor.HasError();
diff --git a/tools/aapt2/link/XmlReferenceLinker_test.cpp b/tools/aapt2/link/XmlReferenceLinker_test.cpp
index 0ce2e50d6e44..ddf5b9a22c2f 100644
--- a/tools/aapt2/link/XmlReferenceLinker_test.cpp
+++ b/tools/aapt2/link/XmlReferenceLinker_test.cpp
@@ -91,7 +91,7 @@ TEST_F(XmlReferenceLinkerTest, LinkBasicAttributes) {
             nonAaptAttrRef="@id/id"
             class="hello" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* view_el = doc->root.get();
@@ -144,7 +144,7 @@ TEST_F(XmlReferenceLinkerTest, PrivateSymbolsAreNotLinked) {
       <View xmlns:android="http://schemas.android.com/apk/res/android"
           android:colorAccent="@android:color/hidden" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_FALSE(linker.Consume(context_.get(), doc.get()));
 }
 
@@ -153,7 +153,7 @@ TEST_F(XmlReferenceLinkerTest, PrivateSymbolsAreLinkedWhenReferenceHasStarPrefix
     <View xmlns:android="http://schemas.android.com/apk/res/android"
           android:colorAccent="@*android:color/hidden" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 }
 
@@ -162,7 +162,7 @@ TEST_F(XmlReferenceLinkerTest, LinkMangledAttributes) {
       <View xmlns:support="http://schemas.android.com/apk/res/com.android.support"
           support:colorAccent="#ff0000" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* view_el = doc->root.get();
@@ -181,7 +181,7 @@ TEST_F(XmlReferenceLinkerTest, LinkAutoResReference) {
       <View xmlns:app="http://schemas.android.com/apk/res-auto"
           app:colorAccent="@app:color/red" />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* view_el = doc->root.get();
@@ -203,7 +203,7 @@ TEST_F(XmlReferenceLinkerTest, LinkViewWithShadowedPackageAlias) {
         <View xmlns:app="http://schemas.android.com/apk/res/com.app.test" app:attr="@app:id/id"/>
       </View>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* view_el = doc->root.get();
@@ -239,7 +239,7 @@ TEST_F(XmlReferenceLinkerTest, LinkViewWithLocalPackageAndAliasOfTheSameName) {
       <View xmlns:android="http://schemas.android.com/apk/res/com.app.test"
           android:attr="@id/id"/>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* view_el = doc->root.get();
@@ -261,7 +261,7 @@ TEST_F(XmlReferenceLinkerTest, AddAngleOnGradientForAndroidQ) {
   std::unique_ptr<xml::XmlResource> doc = test::BuildXmlDomForPackageName(context_.get(), R"(
     <gradient />)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* gradient_el = doc->root.get();
@@ -283,7 +283,7 @@ TEST_F(XmlReferenceLinkerTest, DoNotOverwriteAngleOnGradientForAndroidQ) {
   <gradient xmlns:android="http://schemas.android.com/apk/res/android"
       android:angle="90"/>)");
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* gradient_el = doc->root.get();
@@ -305,7 +305,7 @@ TEST_F(XmlReferenceLinkerTest, DoNotOverwriteAngleOnGradientForPostAndroidQ) {
   <gradient xmlns:android="http://schemas.android.com/apk/res/android" />)");
   context_->SetMinSdkVersion(30);
 
-  XmlReferenceLinker linker;
+  XmlReferenceLinker linker(nullptr);
   ASSERT_TRUE(linker.Consume(context_.get(), doc.get()));
 
   xml::Element* gradient_el = doc->root.get();
diff --git a/tools/aapt2/xml/XmlPullParser.cpp b/tools/aapt2/xml/XmlPullParser.cpp
index a023494ad8f7..182203d397c3 100644
--- a/tools/aapt2/xml/XmlPullParser.cpp
+++ b/tools/aapt2/xml/XmlPullParser.cpp
@@ -177,6 +177,10 @@ const std::string& XmlPullParser::element_name() const {
   return event_queue_.front().data2;
 }
 
+const std::vector<XmlPullParser::PackageDecl>& XmlPullParser::package_decls() const {
+  return package_aliases_;
+}
+
 XmlPullParser::const_iterator XmlPullParser::begin_attributes() const {
   return event_queue_.front().attributes.begin();
 }
diff --git a/tools/aapt2/xml/XmlPullParser.h b/tools/aapt2/xml/XmlPullParser.h
index 6ebaa285745b..5da2d4b10a4b 100644
--- a/tools/aapt2/xml/XmlPullParser.h
+++ b/tools/aapt2/xml/XmlPullParser.h
@@ -123,6 +123,13 @@ class XmlPullParser : public IPackageDeclStack {
    */
   Maybe<ExtractedPackage> TransformPackageAlias(const android::StringPiece& alias) const override;
 
+  struct PackageDecl {
+    std::string prefix;
+    ExtractedPackage package;
+  };
+
+  const std::vector<PackageDecl>& package_decls() const;
+
   //
   // Remaining methods are for retrieving information about attributes
   // associated with a StartElement.
@@ -180,11 +187,6 @@ class XmlPullParser : public IPackageDeclStack {
   const std::string empty_;
   size_t depth_;
   std::stack<std::string> namespace_uris_;
-
-  struct PackageDecl {
-    std::string prefix;
-    ExtractedPackage package;
-  };
   std::vector<PackageDecl> package_aliases_;
 };