3 files changed, 46 insertions, 13 deletions

diff --git a/tools/aapt2/StringPool_test.cpp b/tools/aapt2/StringPool_test.cpp
index 2b2d348fd17c..562d80ed8cdb 100644
--- a/tools/aapt2/StringPool_test.cpp
+++ b/tools/aapt2/StringPool_test.cpp
@@ -208,7 +208,8 @@ TEST(StringPoolTest, FlattenUtf8) {
     StringPool::Ref ref1 = pool.makeRef(u"hello");
     StringPool::Ref ref2 = pool.makeRef(u"goodbye");
     StringPool::Ref ref3 = pool.makeRef(sLongString);
-    StringPool::StyleRef ref4 = pool.makeRef(StyleString{
+    StringPool::Ref ref4 = pool.makeRef(u"");
+    StringPool::StyleRef ref5 = pool.makeRef(StyleString{
             { u"style" },
             { Span{ { u"b" }, 0, 1 }, Span{ { u"i" }, 2, 3 } }
     });
@@ -217,6 +218,7 @@ TEST(StringPoolTest, FlattenUtf8) {
     EXPECT_EQ(1u, ref2.getIndex());
     EXPECT_EQ(2u, ref3.getIndex());
     EXPECT_EQ(3u, ref4.getIndex());
+    EXPECT_EQ(4u, ref5.getIndex());
 
     BigBuffer buffer(1024);
     StringPool::flattenUtf8(&buffer, pool);
@@ -229,9 +231,11 @@ TEST(StringPoolTest, FlattenUtf8) {
         EXPECT_EQ(util::getString(test, 0), u"hello");
         EXPECT_EQ(util::getString(test, 1), u"goodbye");
         EXPECT_EQ(util::getString(test, 2), sLongString);
-        EXPECT_EQ(util::getString(test, 3), u"style");
+        size_t len;
+        EXPECT_NE(nullptr, test.stringAt(3, &len));
+        EXPECT_EQ(util::getString(test, 4), u"style");
 
-        const ResStringPool_span* span = test.styleAt(3);
+        const ResStringPool_span* span = test.styleAt(4);
         ASSERT_NE(nullptr, span);
         EXPECT_EQ(util::getString(test, span->name.index), u"b");
         EXPECT_EQ(0u, span->firstChar);
diff --git a/tools/aapt2/flatten/XmlFlattener.cpp b/tools/aapt2/flatten/XmlFlattener.cpp
index cc457890ff6f..2cf7ddaa2cc6 100644
--- a/tools/aapt2/flatten/XmlFlattener.cpp
+++ b/tools/aapt2/flatten/XmlFlattener.cpp
@@ -57,14 +57,15 @@ struct XmlFlattenerVisitor : public xml::Visitor {
             mBuffer(buffer), mOptions(options) {
     }
 
-    void addString(const StringPiece16& str, uint32_t priority, android::ResStringPool_ref* dest) {
-        if (!str.empty()) {
+    void addString(const StringPiece16& str, uint32_t priority, android::ResStringPool_ref* dest,
+                   bool treatEmptyStringAsNull = false) {
+        if (str.empty() && treatEmptyStringAsNull) {
+            // Some parts of the runtime treat null differently than empty string.
+            dest->index = util::deviceToHost32(-1);
+        } else {
             mStringRefs.push_back(StringFlattenDest{
                     mPool.makeRef(str, StringPool::Context{ priority }),
                     dest });
-        } else {
-            // The device doesn't think a string of size 0 is the same as null.
-            dest->index = util::deviceToHost32(-1);
         }
     }
 
@@ -118,8 +119,14 @@ struct XmlFlattenerVisitor : public xml::Visitor {
             flatNode->comment.index = util::hostToDevice32(-1);
 
             ResXMLTree_attrExt* flatElem = startWriter.nextBlock<ResXMLTree_attrExt>();
-            addString(node->namespaceUri, kLowPriority, &flatElem->ns);
-            addString(node->name, kLowPriority, &flatElem->name);
+
+            // A missing namespace must be null, not an empty string. Otherwise the runtime
+            // complains.
+            addString(node->namespaceUri, kLowPriority, &flatElem->ns,
+                      true /* treatEmptyStringAsNull */);
+            addString(node->name, kLowPriority, &flatElem->name,
+                      true /* treatEmptyStringAsNull */);
+
             flatElem->attributeStart = util::hostToDevice16(sizeof(*flatElem));
             flatElem->attributeSize = util::hostToDevice16(sizeof(ResXMLTree_attribute));
 
@@ -138,7 +145,8 @@ struct XmlFlattenerVisitor : public xml::Visitor {
             flatEndNode->comment.index = util::hostToDevice32(-1);
 
             ResXMLTree_endElementExt* flatEndElem = endWriter.nextBlock<ResXMLTree_endElementExt>();
-            addString(node->namespaceUri, kLowPriority, &flatEndElem->ns);
+            addString(node->namespaceUri, kLowPriority, &flatEndElem->ns,
+                      true /* treatEmptyStringAsNull */);
             addString(node->name, kLowPriority, &flatEndElem->name);
 
             endWriter.finish();
@@ -205,8 +213,10 @@ struct XmlFlattenerVisitor : public xml::Visitor {
             }
             attributeIndex++;
 
-            // Add the namespaceUri to the list of StringRefs to encode.
-            addString(xmlAttr->namespaceUri, kLowPriority, &flatAttr->ns);
+            // Add the namespaceUri to the list of StringRefs to encode. Use null if the namespace
+            // is empty (doesn't exist).
+            addString(xmlAttr->namespaceUri, kLowPriority, &flatAttr->ns,
+                      true /* treatEmptyStringAsNull */);
 
             flatAttr->rawValue.index = util::hostToDevice32(-1);
 
diff --git a/tools/aapt2/flatten/XmlFlattener_test.cpp b/tools/aapt2/flatten/XmlFlattener_test.cpp
index 4e6eb811e572..ef06528e236e 100644
--- a/tools/aapt2/flatten/XmlFlattener_test.cpp
+++ b/tools/aapt2/flatten/XmlFlattener_test.cpp
@@ -207,4 +207,23 @@ TEST_F(XmlFlattenerTest, NoNamespaceIsNotTheSameAsEmptyNamespace) {
     EXPECT_GE(tree.indexOfAttribute(nullptr, 0, kPackage.data(), kPackage.size()), 0);
 }
 
+TEST_F(XmlFlattenerTest, EmptyStringValueInAttributeIsNotNull) {
+    std::unique_ptr<xml::XmlResource> doc = test::buildXmlDom("<View package=\"\"/>");
+
+    android::ResXMLTree tree;
+    ASSERT_TRUE(flatten(doc.get(), &tree));
+
+    while (tree.next() != android::ResXMLTree::START_TAG) {
+        ASSERT_NE(tree.getEventType(), android::ResXMLTree::BAD_DOCUMENT);
+        ASSERT_NE(tree.getEventType(), android::ResXMLTree::END_DOCUMENT);
+    }
+
+    const StringPiece16 kPackage = u"package";
+    ssize_t idx = tree.indexOfAttribute(nullptr, 0, kPackage.data(), kPackage.size());
+    ASSERT_GE(idx, 0);
+
+    size_t len;
+    EXPECT_NE(nullptr, tree.getAttributeStringValue(idx, &len));
+}
+
 } // namespace aapt