[9.0.0] Make --incompatible_enable_proto_toolchain_resolution default to true in Bazel (#28182)

This change updates the default value of the
--incompatible_enable_proto_toolchain_resolution flag to true for Bazel
builds.

The flag's default value and name are now defined in FlagConstants, with
different values for the open-source and internal versions.

PiperOrigin-RevId: 844684939
Change-Id: I264db1921e52e885d1e211f2a627d42ce380bd41

Co-authored-by: ilist <ilist@google.com>

Author: Wyverald

src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java

@@ -643,7 +643,7 @@ public final class BuildLanguageOptions extends OptionsBase {
   // Flip when dependencies to rules_* repos are upgraded and protobuf registers toolchains
   @Option(
       name = "incompatible_enable_proto_toolchain_resolution",
-      defaultValue = "false",
+      defaultValue = FlagConstants.DEFAULT_INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION,
       documentationCategory = OptionDocumentationCategory.TOOLCHAIN,
       effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS},
       metadataTags = {OptionMetadataTag.INCOMPATIBLE_CHANGE},
@@ -1109,7 +1109,7 @@ public FlagConsumer setBool(String key, boolean ignored) {
   public static final String INCOMPATIBLE_FAIL_ON_UNKNOWN_ATTRIBUTES =
       "+incompatible_fail_on_unknown_attributes";
   public static final String INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION =
-      "-incompatible_enable_proto_toolchain_resolution";
+      FlagConstants.DEFAULT_INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION_NAME;
   public static final String INCOMPATIBLE_DISABLE_NON_EXECUTABLE_JAVA_BINARY =
       "-incompatible_disable_non_executable_java_binary";
   public static final String INCOMPATIBLE_DISABLE_TARGET_DEFAULT_PROVIDER_FIELDS =

src/main/java/com/google/devtools/build/lib/packages/semantics/FlagConstants.java

@@ -44,4 +44,8 @@ private FlagConstants() {}
       "+incompatible_package_group_has_public_syntax";
   public static final String INCOMPATIBLE_FIX_PACKAGE_GROUP_REPOROOT_SYNTAX =
       "+incompatible_fix_package_group_reporoot_syntax";
+
+  public static final String DEFAULT_INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION = "true";
+  public static final String DEFAULT_INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION_NAME =
+      "+incompatible_enable_proto_toolchain_resolution";
 }

src/test/java/com/google/devtools/build/lib/rules/java/proto/StarlarkJavaLiteProtoLibraryTest.java

@@ -58,6 +58,7 @@ public class StarlarkJavaLiteProtoLibraryTest extends BuildViewTestCase {
 
   @Before
   public final void setUpMocks() throws Exception {
+    setBuildLanguageOptions("--incompatible_enable_proto_toolchain_resolution=false");
     useConfiguration(
         "--proto_compiler=//proto:compiler",
         "--proto_toolchain_for_javalite=//tools/proto/toolchains:javalite");