[view-compiler] Add layout validation

Layout validation walks over a layout resource and verifies that the layout only
uses features the layout compiler supports.

Currently this means we reject layouts that use any of the following tags:
  * include
  * fragment
  * merge
  * view

In the future, we will extend the layout compiler to handle these, but for now
we want to be liberal in what we reject.

Bug: 111895153
Test: atest view-compiler-tests
Change-Id: I8dca30c035a83b6763497a36fc60c68438fa1b0c

7 files changed, 363 insertions, 1 deletions

diff --git a/startop/view_compiler/Android.bp b/startop/view_compiler/Android.bp
index de40e0df48e7..91cec554d7cd 100644
--- a/startop/view_compiler/Android.bp
+++ b/startop/view_compiler/Android.bp
@@ -24,6 +24,9 @@ cc_defaults {
         "libdexfile",
         "slicer",
     ],
+    static_libs: [
+        "libtinyxml2",
+    ],
 }
 
 cc_library_host_static {
@@ -32,7 +35,9 @@ cc_library_host_static {
     srcs: [
         "dex_builder.cc",
         "java_lang_builder.cc",
+        "tinyxml_layout_parser.cc",
         "util.cc",
+        "layout_validation.cc",
     ],
 }
 
@@ -43,7 +48,6 @@ cc_binary_host {
         "main.cc",
     ],
     static_libs: [
-        "libtinyxml2",
         "libgflags",
         "libviewcompiler",
     ],
@@ -54,6 +58,7 @@ cc_test_host {
     defaults: ["viewcompiler_defaults"],
     srcs: [
         "dex_builder_test.cc",
+        "layout_validation_test.cc",
         "util_test.cc",
     ],
     static_libs: [
diff --git a/startop/view_compiler/layout_validation.cc b/startop/view_compiler/layout_validation.cc
new file mode 100644
index 000000000000..8c7737749124
--- /dev/null
+++ b/startop/view_compiler/layout_validation.cc
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "layout_validation.h"
+
+#include "android-base/stringprintf.h"
+
+namespace startop {
+
+void LayoutValidationVisitor::VisitStartTag(const std::u16string& name) {
+  if (0 == name.compare(u"merge")) {
+    message_ = "Merge tags are not supported";
+    can_compile_ = false;
+  }
+  if (0 == name.compare(u"include")) {
+    message_ = "Include tags are not supported";
+    can_compile_ = false;
+  }
+  if (0 == name.compare(u"view")) {
+    message_ = "View tags are not supported";
+    can_compile_ = false;
+  }
+  if (0 == name.compare(u"fragment")) {
+    message_ = "Fragment tags are not supported";
+    can_compile_ = false;
+  }
+}
+
+}  // namespace startop
\ No newline at end of file
diff --git a/startop/view_compiler/layout_validation.h b/startop/view_compiler/layout_validation.h
new file mode 100644
index 000000000000..bed34bb38e5e
--- /dev/null
+++ b/startop/view_compiler/layout_validation.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LAYOUT_VALIDATION_H_
+#define LAYOUT_VALIDATION_H_
+
+#include "dex_builder.h"
+
+#include <string>
+
+namespace startop {
+
+// This visitor determines whether a layout can be compiled. Since we do not currently support all
+// features, such as includes and merges, we need to pre-validate the layout before we start
+// compiling.
+class LayoutValidationVisitor {
+ public:
+  void VisitStartDocument() const {}
+  void VisitEndDocument() const {}
+  void VisitStartTag(const std::u16string& name);
+  void VisitEndTag() const {}
+
+  const std::string& message() const { return message_; }
+  bool can_compile() const { return can_compile_; }
+
+ private:
+  std::string message_{"Okay"};
+  bool can_compile_{true};
+};
+
+}  // namespace startop
+
+#endif  // LAYOUT_VALIDATION_H_
diff --git a/startop/view_compiler/layout_validation_test.cc b/startop/view_compiler/layout_validation_test.cc
new file mode 100644
index 000000000000..b74cdae8d725
--- /dev/null
+++ b/startop/view_compiler/layout_validation_test.cc
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "tinyxml_layout_parser.h"
+
+#include "gtest/gtest.h"
+
+using startop::CanCompileLayout;
+using std::string;
+
+namespace {
+void ValidateXmlText(const string& xml, bool expected) {
+  tinyxml2::XMLDocument doc;
+  doc.Parse(xml.c_str());
+  EXPECT_EQ(CanCompileLayout(doc), expected);
+}
+}  // namespace
+
+TEST(LayoutValidationTest, SingleButtonLayout) {
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<Button xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:text="Hello, World!">
+
+</Button>)";
+  ValidateXmlText(xml, /*expected=*/true);
+}
+
+TEST(LayoutValidationTest, SmallConstraintLayout) {
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <Button
+        android:id="@+id/button6"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginEnd="16dp"
+        android:layout_marginBottom="16dp"
+        android:text="Button"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+    <Button
+        android:id="@+id/button7"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginEnd="8dp"
+        android:layout_marginBottom="16dp"
+        android:text="Button2"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/button6" />
+
+    <Button
+        android:id="@+id/button8"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginEnd="8dp"
+        android:layout_marginBottom="16dp"
+        android:text="Button1"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/button7" />
+</android.support.constraint.ConstraintLayout>)";
+  ValidateXmlText(xml, /*expected=*/true);
+}
+
+TEST(LayoutValidationTest, MergeNode) {
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<merge xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <TextView
+        android:id="@+id/textView3"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="TextView" />
+
+    <Button
+        android:id="@+id/button9"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Button" />
+</merge>)";
+  ValidateXmlText(xml, /*expected=*/false);
+}
+
+TEST(LayoutValidationTest, IncludeLayout) {
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <include
+        layout="@layout/single_button_layout"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+</android.support.constraint.ConstraintLayout>)";
+  ValidateXmlText(xml, /*expected=*/false);
+}
+
+TEST(LayoutValidationTest, ViewNode) {
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <view
+        class="android.support.design.button.MaterialButton"
+        id="@+id/view"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+</android.support.constraint.ConstraintLayout>)";
+  ValidateXmlText(xml, /*expected=*/false);
+}
+
+TEST(LayoutValidationTest, FragmentNode) {
+  // This test case is from https://developer.android.com/guide/components/fragments
+  const string xml = R"(<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:orientation="horizontal"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+    <fragment android:name="com.example.news.ArticleListFragment"
+            android:id="@+id/list"
+            android:layout_weight="1"
+            android:layout_width="0dp"
+            android:layout_height="match_parent" />
+    <fragment android:name="com.example.news.ArticleReaderFragment"
+            android:id="@+id/viewer"
+            android:layout_weight="2"
+            android:layout_width="0dp"
+            android:layout_height="match_parent" />
+</LinearLayout>)";
+  ValidateXmlText(xml, /*expected=*/false);
+}
diff --git a/startop/view_compiler/main.cc b/startop/view_compiler/main.cc
index 7d791c229a98..9351dc34ea54 100644
--- a/startop/view_compiler/main.cc
+++ b/startop/view_compiler/main.cc
@@ -18,6 +18,7 @@
 
 #include "dex_builder.h"
 #include "java_lang_builder.h"
+#include "tinyxml_layout_parser.h"
 #include "util.h"
 
 #include "tinyxml2.h"
@@ -100,6 +101,12 @@ int main(int argc, char** argv) {
   XMLDocument xml;
   xml.LoadFile(filename);
 
+  string message{};
+  if (!startop::CanCompileLayout(xml, &message)) {
+    LOG(ERROR) << "Layout not supported: " << message;
+    return 1;
+  }
+
   std::ofstream outfile;
   if (FLAGS_out != kStdoutFilename) {
     outfile.open(FLAGS_out);
diff --git a/startop/view_compiler/tinyxml_layout_parser.cc b/startop/view_compiler/tinyxml_layout_parser.cc
new file mode 100644
index 000000000000..1b3a81f17976
--- /dev/null
+++ b/startop/view_compiler/tinyxml_layout_parser.cc
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "tinyxml_layout_parser.h"
+
+#include "layout_validation.h"
+
+namespace startop {
+
+bool CanCompileLayout(const tinyxml2::XMLDocument& xml, std::string* message) {
+  LayoutValidationVisitor validator;
+  TinyXmlVisitorAdapter adapter{&validator};
+  xml.Accept(&adapter);
+
+  if (message != nullptr) {
+    *message = validator.message();
+  }
+
+  return validator.can_compile();
+}
+
+}  // namespace startop
diff --git a/startop/view_compiler/tinyxml_layout_parser.h b/startop/view_compiler/tinyxml_layout_parser.h
new file mode 100644
index 000000000000..8f714a2c5a3f
--- /dev/null
+++ b/startop/view_compiler/tinyxml_layout_parser.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef TINYXML_LAYOUT_PARSER_H_
+#define TINYXML_LAYOUT_PARSER_H_
+
+#include "tinyxml2.h"
+
+#include <codecvt>
+#include <locale>
+#include <string>
+
+namespace startop {
+
+template <typename Visitor>
+class TinyXmlVisitorAdapter : public tinyxml2::XMLVisitor {
+ public:
+  explicit TinyXmlVisitorAdapter(Visitor* visitor) : visitor_{visitor} {}
+
+  bool VisitEnter(const tinyxml2::XMLDocument& /*doc*/) override {
+    visitor_->VisitStartDocument();
+    return true;
+  }
+
+  bool VisitExit(const tinyxml2::XMLDocument& /*doc*/) override {
+    visitor_->VisitEndDocument();
+    return true;
+  }
+
+  bool VisitEnter(const tinyxml2::XMLElement& element,
+                  const tinyxml2::XMLAttribute* /*firstAttribute*/) override {
+    visitor_->VisitStartTag(
+        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}.from_bytes(
+            element.Name()));
+    return true;
+  }
+
+  bool VisitExit(const tinyxml2::XMLElement& /*element*/) override {
+    visitor_->VisitEndTag();
+    return true;
+  }
+
+ private:
+  Visitor* visitor_;
+};
+
+// Returns whether a layout resource represented by a TinyXML document is supported by the layout
+// compiler.
+bool CanCompileLayout(const tinyxml2::XMLDocument& xml, std::string* message = nullptr);
+
+}  // namespace startop
+
+#endif  // TINYXML_LAYOUT_PARSER_H_