Backport stubs / tests for compatibility with <4.26.x gencode to 27.x

.github/workflows/test_java.yml

@@ -22,19 +22,19 @@ jobs:
             image: us-docker.pkg.dev/protobuf-build/containers/test/linux/java:8-1fdbb997433cb22c1e49ef75ad374a8d6bb88702
             # TODO: b/318555165 - enable the layering check. Currently it does
             # not work correctly with the toolchain in this Docker image.
-            targets: //java/... //java/internal:java_version --features=-layering_check
+            targets: //java/... //java/internal:java_version //compatibility/... --features=-layering_check
           - name: OpenJDK 11
             version: '11'
             image: us-docker.pkg.dev/protobuf-build/containers/test/linux/java:11-1fdbb997433cb22c1e49ef75ad374a8d6bb88702
-            targets: //java/... //java/internal:java_version
+            targets: //java/... //java/internal:java_version //compatibility/...
           - name: OpenJDK 17
             version: '17'
             image: us-docker.pkg.dev/protobuf-build/containers/test/linux/java:17-1fdbb997433cb22c1e49ef75ad374a8d6bb88702
-            targets: //java/... //java/internal:java_version
+            targets: //java/... //java/internal:java_version //compatibility/...
           - name: aarch64
             version: 'aarch64'
             image: us-docker.pkg.dev/protobuf-build/containers/test/linux/emulation:aarch64-63dd26c0c7a808d92673a3e52e848189d4ab0f17
-            targets: //java/... //src/google/protobuf/compiler:protoc_aarch64_test
+            targets: //java/... //compatibility/... //src/google/protobuf/compiler:protoc_aarch64_test
 
     name: Linux ${{ matrix.name }}
     runs-on: ubuntu-latest

WORKSPACE

@@ -225,3 +225,18 @@ crates_repository(
 
 load("@crate_index//:defs.bzl", "crate_repositories")
 crate_repositories()
+
+# For testing runtime against old gencode from a previous major version.
+http_archive(
+    name = "com_google_protobuf_v25.0",
+    strip_prefix = "protobuf-25.0",
+    url = "https://github.com/protocolbuffers/protobuf/releases/download/v25.0/protobuf-25.0.tar.gz",
+)
+
+# Needed as a dependency of @com_google_protobuf_v25.x, which was before
+# utf8_range was merged in.
+http_archive(
+    name = "utf8_range",
+    strip_prefix = "utf8_range-d863bc33e15cba6d873c878dcca9e6fe52b2f8cb",
+    url = "https://github.com/protocolbuffers/utf8_range/archive/d863bc33e15cba6d873c878dcca9e6fe52b2f8cb.zip",
+)

compatibility/BUILD.bazel

@@ -0,0 +1,19 @@
+# Simple build tests for compatibility of gencode from previous major versions
+# with the current runtime.
+#
+# To add more test cases in Java, use java_runtime_conformance as below, and add
+# the corresponding http_archive in the WORKSPACE file for the version.
+
+load("//compatibility:runtime_conformance.bzl", "java_runtime_conformance")
+
+# main gencode builds with main runtime as a proof of concept.
+java_runtime_conformance(
+    name = "java_conformance_main",
+    gencode_version = "main",
+)
+
+# Generates a build_test named "conformance_v3.25.0"
+java_runtime_conformance(
+    name = "java_conformance_v3.25.0",
+    gencode_version = "3.25.0",
+)

compatibility/runtime_conformance.bzl

@@ -0,0 +1,53 @@
+"""Provides a rule to generate a conformance test for a given version of the gencode."""
+
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+
+def java_runtime_conformance(name, gencode_version, tags = []):
+    """Generates a conformance test for the given version of the runtime.
+
+    For example, runtime_conformance("3.19.4") will generate a build test named "conformance_v3.19.4"
+    that will fail if the runtime at that version fails to compile the unittest proto.
+
+    Args:
+        name: The name of the test.
+        gencode_version: The version of the runtime to test.
+        tags: Any tags to apply to the generated test.
+    """
+
+    if gencode_version == "main":
+        protoc = "//:protoc"
+    else:
+        minor = gencode_version[gencode_version.find(".") + 1:]
+        protoc = Label("@com_google_protobuf_v%s//:protoc" % minor)
+
+    gencode = [
+        "v%s/protobuf_unittest/UnittestProto.java" % gencode_version,
+        "v%s/com/google/protobuf/test/UnittestImport.java" % gencode_version,
+        "v%s/com/google/protobuf/test/UnittestImportPublic.java" % gencode_version,
+    ]
+    native.genrule(
+        name = "unittest_proto_gencode_v" + gencode_version,
+        srcs = [
+            "//src/google/protobuf:unittest_proto_srcs",
+        ],
+        outs = gencode,
+        cmd = "$(location %s) " % protoc +
+              "$(locations //src/google/protobuf:unittest_proto_srcs) " +
+              " -Isrc/ --java_out=$(@D)/v%s" % gencode_version,
+        tools = [protoc],
+    )
+
+    conformance_name = "conformance_v" + gencode_version
+    conformance_lib_name = conformance_name + "_lib"
+    native.java_library(
+        name = conformance_lib_name,
+        srcs = gencode,
+        deps = ["//java/core"],
+        tags = tags,
+    )
+
+    build_test(
+        name = name,
+        targets = [":" + conformance_lib_name],
+        tags = tags,
+    )

java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java

@@ -0,0 +1,83 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  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 java.util.List;
+
+/**
+ * Stub for GeneratedMessageV3 wrapping GeneratedMessage for compatibility with older gencode.
+ *
+ * @deprecated This class is deprecated, and slated for removal in the next Java breaking change
+ *     (5.x in 2025 Q1). Users should update gencode to >= 4.26.x which uses GeneratedMessage
+ *     instead of GeneratedMessageV3.
+ */
+@Deprecated
+public abstract class GeneratedMessageV3 extends GeneratedMessage {
+  private static final long serialVersionUID = 1L;
+
+  protected GeneratedMessageV3() {
+    super();
+  }
+
+  protected GeneratedMessageV3(Builder<?> builder) {
+    super(builder);
+  }
+
+  /**
+   * Stub for GeneratedMessageV3.ExtendableBuilder wrapping GeneratedMessage.ExtendableBuilder for
+   * compatibility with older gencode.
+   *
+   * @deprecated This class is deprecated, and slated for removal in the next Java breaking change
+   *     (5.x in 2025 Q1). Users should update gencode to >= 4.26.x which uses
+   *     GeneratedMessage.ExtendableBuilder instead of GeneratedMessageV3.ExtendableBuilder.
+   */
+  @Deprecated
+  public abstract static class ExtendableBuilder<
+          MessageT extends ExtendableMessage<MessageT>,
+          BuilderT extends ExtendableBuilder<MessageT, BuilderT>>
+      extends GeneratedMessage.ExtendableBuilder<MessageT, BuilderT>
+      implements GeneratedMessage.ExtendableMessageOrBuilder<MessageT> {
+    protected ExtendableBuilder() {
+      super();
+    }
+
+    protected ExtendableBuilder(BuilderParent parent) {
+      super(parent);
+    }
+
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
+    public <T> BuilderT setExtension(
+        final GeneratedMessage.GeneratedExtension<MessageT, T> extension, final T value) {
+      return setExtension((ExtensionLite<MessageT, T>) extension, value);
+    }
+
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
+    public <T> BuilderT setExtension(
+        final GeneratedMessage.GeneratedExtension<MessageT, List<T>> extension,
+        final int index,
+        final T value) {
+      return setExtension((ExtensionLite<MessageT, List<T>>) extension, index, value);
+    }
+
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
+    public <T> BuilderT addExtension(
+        final GeneratedMessage.GeneratedExtension<MessageT, List<T>> extension, final T value) {
+      return addExtension((ExtensionLite<MessageT, List<T>>) extension, value);
+    }
+
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
+    public <T> BuilderT clearExtension(
+        final GeneratedMessage.GeneratedExtension<MessageT, T> extension) {
+      return clearExtension((ExtensionLite<MessageT, T>) extension);
+    }
+  }
+}

java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilderV3.java

@@ -0,0 +1,34 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  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 java.util.List;
+
+/**
+ * Stub for RepeatedFieldBuilderV3 wrapping RepeatedFieldBuilder for compatibility with older
+ * gencode.
+ *
+ * @deprecated This class is deprecated, and slated for removal in the next breaking change. Users
+ *     should update gencode to >= 4.26.x which replaces RepeatedFieldBuilderV3 with
+ *     RepeatedFieldBuilder.
+ */
+@Deprecated
+public class RepeatedFieldBuilderV3<
+        MType extends GeneratedMessage,
+        BType extends GeneratedMessage.Builder,
+        IType extends MessageOrBuilder>
+    extends RepeatedFieldBuilder<MType, BType, IType> {
+
+  public RepeatedFieldBuilderV3(
+      List<MType> messages,
+      boolean isMessagesListMutable,
+      GeneratedMessage.BuilderParent parent,
+      boolean isClean) {
+    super(messages, isMessagesListMutable, parent, isClean);
+  }
+}

java/core/src/main/java/com/google/protobuf/SingleFieldBuilderV3.java

@@ -0,0 +1,28 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  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;
+
+/**
+ * Stub for SingleFieldBuilderV3 wrapping SingleFieldBuilder for compatibility with older gencode.
+ *
+ * @deprecated This class is deprecated, and slated for removal in the next breaking change. Users
+ *     should update gencode to >= 4.26.x which replaces SingleFieldBuilderV3 with
+ *     SingleFieldBuilder.
+ */
+@Deprecated
+public class SingleFieldBuilderV3<
+        MType extends GeneratedMessage,
+        BType extends GeneratedMessage.Builder,
+        IType extends MessageOrBuilder>
+    extends SingleFieldBuilder<MType, BType, IType> {
+
+  public SingleFieldBuilderV3(
+      MType message, GeneratedMessage.BuilderParent parent, boolean isClean) {
+    super(message, parent, isClean);
+  }
+}

src/google/protobuf/BUILD.bazel

@@ -840,6 +840,16 @@ filegroup(
     visibility = ["//:__subpackages__"],
 )
 
+filegroup(
+    name = "unittest_proto_srcs",
+    srcs = [
+        "unittest.proto",
+        "unittest_import.proto",
+        "unittest_import_public.proto",
+    ],
+    visibility = ["//:__subpackages__"],
+)
+
 filegroup(
     name = "test_proto_editions_srcs",
     srcs = [