[aapt2] Generate @FlaggedApi annotations

Like we currently do for @TestApi and @SystemApi, we look for
"@FlaggedApi" and its parameters in the comment above the resource.

Bug: 295328308
Test: Did the following:
1. Ran `atest aapt2_tests`
2. Ran `aapt2 link` on public-staging.xml with an added @FlaggedApi
   in the comment for the resource currently there. Verified the
   @FlaggedApi annotation is present in the generated R.java.
3. Ran `m framework-minus-apex` and it built successfully.
4. Modified the @FlaggedApi comment with an invalid value (e.g.,
   `Flags.FOO` which does not exist). The build failed. Since
   @FlaggedApi is a source-only annotation (i.e., not present in the
   R.class file), we want to verify it was actually used in the build.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6fa7a3c7c5213ad3a94406f46fec6d1219b3fa43)
Merged-In: I0739f888d40269915c0acea5650c386da1a1782e
Change-Id: I0739f888d40269915c0acea5650c386da1a1782e

2 files changed, 39 insertions, 7 deletions

diff --git a/tools/aapt2/java/AnnotationProcessor.cpp b/tools/aapt2/java/AnnotationProcessor.cpp
index 87da09a7b054..8c644cf83339 100644
--- a/tools/aapt2/java/AnnotationProcessor.cpp
+++ b/tools/aapt2/java/AnnotationProcessor.cpp
@@ -49,16 +49,19 @@ struct AnnotationRule {
     kDeprecated = 0x01,
     kSystemApi = 0x02,
     kTestApi = 0x04,
+    kFlaggedApi = 0x08,
   };
 
   StringPiece doc_str;
   uint32_t bit_mask;
   StringPiece annotation;
+  bool preserve_params;
 };
 
-static std::array<AnnotationRule, 2> sAnnotationRules = {{
-    {"@SystemApi", AnnotationRule::kSystemApi, "@android.annotation.SystemApi"},
-    {"@TestApi", AnnotationRule::kTestApi, "@android.annotation.TestApi"},
+static std::array<AnnotationRule, 3> sAnnotationRules = {{
+    {"@SystemApi", AnnotationRule::kSystemApi, "@android.annotation.SystemApi", true},
+    {"@TestApi", AnnotationRule::kTestApi, "@android.annotation.TestApi", false},
+    {"@FlaggedApi", AnnotationRule::kFlaggedApi, "@android.annotation.FlaggedApi", true},
 }};
 
 void AnnotationProcessor::AppendCommentLine(std::string comment) {
@@ -73,12 +76,11 @@ void AnnotationProcessor::AppendCommentLine(std::string comment) {
     std::string::size_type idx = comment.find(rule.doc_str.data());
     if (idx != std::string::npos) {
       // Captures all parameters associated with the specified annotation rule
-      // by matching the first pair of parantheses after the rule.
-      std::regex re(std::string(rule.doc_str) += "\\s*\\((.+)\\)");
+      // by matching the first pair of parentheses after the rule.
+      std::regex re(std::string(rule.doc_str).append(R"(\s*\((.+)\))"));
       std::smatch match_result;
       const bool is_match = std::regex_search(comment, match_result, re);
-      // We currently only capture and preserve parameters for SystemApi.
-      if (is_match && rule.bit_mask == AnnotationRule::kSystemApi) {
+      if (is_match && rule.preserve_params) {
         annotation_parameter_map_[rule.bit_mask] = match_result[1].str();
         comment.erase(comment.begin() + match_result.position(),
                       comment.begin() + match_result.position() + match_result.length());
diff --git a/tools/aapt2/java/AnnotationProcessor_test.cpp b/tools/aapt2/java/AnnotationProcessor_test.cpp
index 6bc8902a6dcf..e98e96ba3bc3 100644
--- a/tools/aapt2/java/AnnotationProcessor_test.cpp
+++ b/tools/aapt2/java/AnnotationProcessor_test.cpp
@@ -76,6 +76,36 @@ TEST(AnnotationProcessorTest, EmitsSystemApiAnnotationParamsAndRemovesFromCommen
   EXPECT_THAT(annotations, HasSubstr("This is a system API"));
 }
 
+TEST(AnnotationProcessorTest, EmitsFlaggedApiAnnotationAndRemovesFromComment) {
+  AnnotationProcessor processor;
+  processor.AppendComment("@FlaggedApi This is a flagged API");
+
+  std::string annotations;
+  StringOutputStream out(&annotations);
+  Printer printer(&out);
+  processor.Print(&printer);
+  out.Flush();
+
+  EXPECT_THAT(annotations, HasSubstr("@android.annotation.FlaggedApi"));
+  EXPECT_THAT(annotations, Not(HasSubstr("@FlaggedApi")));
+  EXPECT_THAT(annotations, HasSubstr("This is a flagged API"));
+}
+
+TEST(AnnotationProcessorTest, EmitsFlaggedApiAnnotationParamsAndRemovesFromComment) {
+  AnnotationProcessor processor;
+  processor.AppendComment("@FlaggedApi (\"android.flags.my_flag\") This is a flagged API");
+
+  std::string annotations;
+  StringOutputStream out(&annotations);
+  Printer printer(&out);
+  processor.Print(&printer);
+  out.Flush();
+
+  EXPECT_THAT(annotations, HasSubstr("@android.annotation.FlaggedApi(\"android.flags.my_flag\")"));
+  EXPECT_THAT(annotations, Not(HasSubstr("@FlaggedApi")));
+  EXPECT_THAT(annotations, HasSubstr("This is a flagged API"));
+}
+
 TEST(AnnotationProcessorTest, EmitsTestApiAnnotationAndRemovesFromComment) {
   AnnotationProcessor processor;
   processor.AppendComment("@TestApi This is a test API");