Merge "[aapt2] Use FeatureFlagsFilter in link command" into main
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index cf4dd79..24699bf 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -56,6 +56,7 @@
 #include "java/JavaClassGenerator.h"
 #include "java/ManifestClassGenerator.h"
 #include "java/ProguardRules.h"
+#include "link/FeatureFlagsFilter.h"
 #include "link/Linkers.h"
 #include "link/ManifestFixer.h"
 #include "link/NoDefaultResourceRemover.h"
@@ -1986,6 +1987,19 @@
     context_->SetNameManglerPolicy(NameManglerPolicy{context_->GetCompilationPackage()});
     context_->SetSplitNameDependencies(app_info_.split_name_dependencies);
 
+    FeatureFlagsFilterOptions flags_filter_options;
+    if (context_->GetMinSdkVersion() > SDK_UPSIDE_DOWN_CAKE) {
+      // For API version > U, PackageManager will dynamically read the flag values and disable
+      // manifest elements accordingly when parsing the manifest.
+      // For API version <= U, we remove disabled elements from the manifest with the filter.
+      flags_filter_options.remove_disabled_elements = false;
+      flags_filter_options.flags_must_have_value = false;
+    }
+    FeatureFlagsFilter flags_filter(options_.feature_flag_values, flags_filter_options);
+    if (!flags_filter.Consume(context_, manifest_xml.get())) {
+      return 1;
+    }
+
     // Override the package ID when it is "android".
     if (context_->GetCompilationPackage() == "android") {
       context_->SetPackageId(kAndroidPackageId);
@@ -2530,7 +2544,7 @@
   }
 
   for (const std::string& arg : all_feature_flags_args) {
-    if (ParseFeatureFlagsParameter(arg, context.GetDiagnostics(), &options_.feature_flag_values)) {
+    if (!ParseFeatureFlagsParameter(arg, context.GetDiagnostics(), &options_.feature_flag_values)) {
       return 1;
     }
   }
diff --git a/tools/aapt2/cmd/Link.h b/tools/aapt2/cmd/Link.h
index 26713fd..dc18b1c 100644
--- a/tools/aapt2/cmd/Link.h
+++ b/tools/aapt2/cmd/Link.h
@@ -330,7 +330,11 @@
             "should only be used together with the --static-lib flag.",
         &options_.merge_only);
     AddOptionalSwitch("-v", "Enables verbose logging.", &verbose_);
-    AddOptionalFlagList("--feature-flags", "Placeholder, to be implemented.", &feature_flags_args_);
+    AddOptionalFlagList("--feature-flags",
+                        "Specify the values of feature flags. The pairs in the argument\n"
+                        "are separated by ',' and the name is separated from the value by '='.\n"
+                        "Example: \"flag1=true,flag2=false,flag3=\" (flag3 has no given value).",
+                        &feature_flags_args_);
   }
 
   int Action(const std::vector<std::string>& args) override;
diff --git a/tools/aapt2/cmd/Link_test.cpp b/tools/aapt2/cmd/Link_test.cpp
index 725a1b8..7ceb351 100644
--- a/tools/aapt2/cmd/Link_test.cpp
+++ b/tools/aapt2/cmd/Link_test.cpp
@@ -16,11 +16,10 @@
 
 #include "Link.h"
 
-#include <android-base/file.h>
-
-#include "AppInfo.h"
 #include "Diagnostics.h"
 #include "LoadedApk.h"
+#include "android-base/file.h"
+#include "android-base/stringprintf.h"
 #include "test/Test.h"
 
 using testing::Eq;
@@ -993,4 +992,213 @@
   ASSERT_FALSE(Link(link_args, &diag));
 }
 
+static void BuildSDKWithFeatureFlagAttr(const std::string& apk_path, const std::string& java_path,
+                                        CommandTestFixture* fixture, android::IDiagnostics* diag) {
+  const std::string android_values =
+      R"(<resources>
+          <staging-public-group type="attr" first-id="0x01fe0063">
+            <public name="featureFlag" />
+          </staging-public-group>
+          <attr name="featureFlag" format="string" />
+         </resources>)";
+
+  SourceXML source_xml{.res_file_path = "/res/values/values.xml", .file_contents = android_values};
+  BuildSDK({source_xml}, apk_path, java_path, fixture, diag);
+}
+
+TEST_F(LinkTest, FeatureFlagDisabled_SdkAtMostUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_UPSIDE_DOWN_CAKE);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=false");
+
+  const std::string app_apk = GetTestPath("app.apk");
+  BuildApk({}, app_apk, std::move(app_link_args), this, &diag);
+
+  // Permission element should be removed if flag is disabled
+  auto apk = LoadedApk::LoadApkFromPath(app_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+  auto apk_manifest = apk->GetManifest();
+  ASSERT_THAT(apk_manifest, NotNull());
+  auto root = apk_manifest->root.get();
+  ASSERT_THAT(root, NotNull());
+  auto maybe_removed = root->FindChild({}, "permission");
+  ASSERT_THAT(maybe_removed, IsNull());
+}
+
+TEST_F(LinkTest, FeatureFlagEnabled_SdkAtMostUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_UPSIDE_DOWN_CAKE);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=true");
+
+  const std::string app_apk = GetTestPath("app.apk");
+  BuildApk({}, app_apk, std::move(app_link_args), this, &diag);
+
+  // Permission element should be kept if flag is enabled
+  auto apk = LoadedApk::LoadApkFromPath(app_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+  auto apk_manifest = apk->GetManifest();
+  ASSERT_THAT(apk_manifest, NotNull());
+  auto root = apk_manifest->root.get();
+  ASSERT_THAT(root, NotNull());
+  auto maybe_removed = root->FindChild({}, "permission");
+  ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST_F(LinkTest, FeatureFlagWithNoValue_SdkAtMostUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_UPSIDE_DOWN_CAKE);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=");
+
+  // Flags must have values if <= UDC
+  const std::string app_apk = GetTestPath("app.apk");
+  ASSERT_FALSE(Link(app_link_args.Build(app_apk), &diag));
+}
+
+TEST_F(LinkTest, FeatureFlagDisabled_SdkAfterUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_CUR_DEVELOPMENT);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=false");
+
+  const std::string app_apk = GetTestPath("app.apk");
+  BuildApk({}, app_apk, std::move(app_link_args), this, &diag);
+
+  // Permission element should be kept if > UDC, regardless of flag value
+  auto apk = LoadedApk::LoadApkFromPath(app_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+  auto apk_manifest = apk->GetManifest();
+  ASSERT_THAT(apk_manifest, NotNull());
+  auto root = apk_manifest->root.get();
+  ASSERT_THAT(root, NotNull());
+  auto maybe_removed = root->FindChild({}, "permission");
+  ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST_F(LinkTest, FeatureFlagEnabled_SdkAfterUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_CUR_DEVELOPMENT);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=true");
+
+  const std::string app_apk = GetTestPath("app.apk");
+  BuildApk({}, app_apk, std::move(app_link_args), this, &diag);
+
+  // Permission element should be kept if > UDC, regardless of flag value
+  auto apk = LoadedApk::LoadApkFromPath(app_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+  auto apk_manifest = apk->GetManifest();
+  ASSERT_THAT(apk_manifest, NotNull());
+  auto root = apk_manifest->root.get();
+  ASSERT_THAT(root, NotNull());
+  auto maybe_removed = root->FindChild({}, "permission");
+  ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST_F(LinkTest, FeatureFlagWithNoValue_SdkAfterUDC) {
+  StdErrDiagnostics diag;
+  const std::string android_apk = GetTestPath("android.apk");
+  const std::string android_java = GetTestPath("android-java");
+  BuildSDKWithFeatureFlagAttr(android_apk, android_java, this, &diag);
+
+  const std::string manifest_contents = android::base::StringPrintf(
+      R"(<uses-sdk android:minSdkVersion="%d" />"
+          <permission android:name="FOO" android:featureFlag="flag" />)",
+      SDK_CUR_DEVELOPMENT);
+  auto app_manifest = ManifestBuilder(this)
+                          .SetPackageName("com.example.app")
+                          .AddContents(manifest_contents)
+                          .Build();
+
+  auto app_link_args = LinkCommandBuilder(this)
+                           .SetManifestFile(app_manifest)
+                           .AddParameter("-I", android_apk)
+                           .AddParameter("--feature-flags", "flag=");
+
+  const std::string app_apk = GetTestPath("app.apk");
+  BuildApk({}, app_apk, std::move(app_link_args), this, &diag);
+
+  // Permission element should be kept if > UDC, regardless of flag value
+  auto apk = LoadedApk::LoadApkFromPath(app_apk, &diag);
+  ASSERT_THAT(apk, NotNull());
+  auto apk_manifest = apk->GetManifest();
+  ASSERT_THAT(apk_manifest, NotNull());
+  auto root = apk_manifest->root.get();
+  ASSERT_THAT(root, NotNull());
+  auto maybe_removed = root->FindChild({}, "permission");
+  ASSERT_THAT(maybe_removed, NotNull());
+}
+
 }  // namespace aapt