Introduce a Generated annotation to eventually replace javax.annotation.Generated

PiperOrigin-RevId: 741569920

Author: acozzette

java/core/BUILD.bazel

@@ -47,6 +47,7 @@ LITE_SRCS = [
     "src/main/java/com/google/protobuf/FieldSet.java",
     "src/main/java/com/google/protobuf/FieldType.java",
     "src/main/java/com/google/protobuf/FloatArrayList.java",
+    "src/main/java/com/google/protobuf/Generated.java",
     "src/main/java/com/google/protobuf/GeneratedMessageInfoFactory.java",
     "src/main/java/com/google/protobuf/GeneratedMessageLite.java",
     "src/main/java/com/google/protobuf/InlineMe.java",

java/core/src/main/java/com/google/protobuf/Generated.java

@@ -0,0 +1,24 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+package com.google.protobuf;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/** Marks protobuf implementations generated by the {@code protoc} compiler. */
+@Documented
+// This is only used for static analysis at the compilation level, so SOURCE retention is used. It
+// also must be SOURCE so that it does not force annotated classes to be forced into a main dex file
+// in Android apks.
+@Retention(SOURCE)
+@Target(TYPE)
+public @interface Generated {}

src/google/protobuf/compiler/java/helpers.cc

@@ -53,9 +53,12 @@ const char kThinSeparator[] =
 void PrintGeneratedAnnotation(io::Printer* printer, char delimiter,
                               absl::string_view annotation_file,
                               Options options) {
+  printer->Print("@com.google.protobuf.Generated\n");
+
   if (annotation_file.empty()) {
     return;
   }
+  // Print javax.annotation.Generated to support Kythe indexing
   std::string ptemplate =
       "@javax.annotation.Generated(value=\"protoc\", comments=\"annotations:";
   ptemplate.push_back(delimiter);