[8.0.0] Put macro attribute inheritance behind an off-by-default --experimental_enable_macro_inherit_attrs flag

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

@@ -244,6 +244,16 @@ public final class BuildLanguageOptions extends OptionsBase {
       help = "If set to true, enables the `macro()` construct for defining symbolic macros.")
   public boolean experimentalEnableFirstClassMacros;
 
+  @Option(
+      name = "experimental_enable_macro_inherit_attrs",
+      defaultValue = "false",
+      documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
+      effectTags = OptionEffectTag.BUILD_FILE_SEMANTICS,
+      help =
+          "If set to true, enables attribute inheritance in symbolic macros and the inherit_attrs"
+              + " parameter in the macro() built-in")
+  public boolean experimentalEnableMacroInheritAttrs;
+
   @Option(
       name = "experimental_enable_scl_dialect",
       defaultValue = "true",
@@ -848,6 +858,7 @@ public StarlarkSemantics toStarlarkSemantics() {
                 EXPERIMENTAL_SINGLE_PACKAGE_TOOLCHAIN_BINDING,
                 experimentalSinglePackageToolchainBinding)
             .setBool(EXPERIMENTAL_ENABLE_FIRST_CLASS_MACROS, experimentalEnableFirstClassMacros)
+            .setBool(EXPERIMENTAL_ENABLE_MACRO_INHERIT_ATTRS, experimentalEnableMacroInheritAttrs)
             .setBool(EXPERIMENTAL_ENABLE_SCL_DIALECT, experimentalEnableSclDialect)
             .setBool(ENABLE_BZLMOD, enableBzlmod)
             .setBool(ENABLE_WORKSPACE, enableWorkspace)
@@ -961,6 +972,8 @@ public StarlarkSemantics toStarlarkSemantics() {
       "-experimental_single_package_toolchain_binding";
   public static final String EXPERIMENTAL_ENABLE_FIRST_CLASS_MACROS =
       "+experimental_enable_first_class_macros";
+  public static final String EXPERIMENTAL_ENABLE_MACRO_INHERIT_ATTRS =
+      "-experimental_enable_macro_inherit_attrs";
   public static final String EXPERIMENTAL_ENABLE_SCL_DIALECT = "+experimental_enable_scl_dialect";
   public static final String ENABLE_BZLMOD = "+enable_bzlmod";
   public static final String ENABLE_WORKSPACE = "-enable_workspace";

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/StarlarkRuleFunctionsApi.java

@@ -263,6 +263,8 @@ site of the rule. Such attributes can be assigned a default value (as in
             positional = false,
             named = true,
             defaultValue = "None",
+            enableOnlyWithFlag = BuildLanguageOptions.EXPERIMENTAL_ENABLE_MACRO_INHERIT_ATTRS,
+            valueWhenDisabled = "None",
             doc =
                 """
 A rule symbol, macro symbol, or the name of a built-in common attribute list (see below) from which

src/test/java/com/google/devtools/build/lib/analysis/SymbolicMacroTest.java

@@ -1582,8 +1582,33 @@ def _impl(name, visibility, **kwargs):
         .doesNotContainKey("disabled_attr");
   }
 
+  @Test
+  public void inheritAttrs_disabledByDefault() throws Exception {
+    scratch.file(
+        "pkg/foo.bzl",
+        """
+        def _my_macro_impl(name, visibility, **kwargs):
+            pass
+
+        my_macro = macro(
+            implementation = _my_macro_impl,
+            inherit_attrs = native.cc_library,
+        )
+        """);
+    scratch.file(
+        "pkg/BUILD",
+        """
+        load(":foo.bzl", "my_macro")
+        """);
+    reporter.removeHandler(failFastHandler);
+    assertThat(getPackage("pkg")).isNull();
+    assertContainsEvent(
+        "parameter 'inherit_attrs' is experimental and thus unavailable with the current flags");
+  }
+
   @Test
   public void inheritAttrs_fromInvalidSource_fails() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/foo.bzl",
         """
@@ -1608,6 +1633,7 @@ def _my_macro_impl(name, visibility, **kwargs):
 
   @Test
   public void inheritAttrs_withoutKwargsInImplementation_fails() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/foo.bzl",
         """
@@ -1632,6 +1658,7 @@ def _my_macro_impl(name, visibility, tags):
 
   @Test
   public void inheritAttrs_fromCommon_withOverrides() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/my_macro.bzl",
         """
@@ -1694,6 +1721,7 @@ public void inheritAttrs_fromAnyNativeRule() throws Exception {
     // * a new AttributeValueSource or a new attribute type is introduced, and symbolic macros
     //   cannot inherit an attribute with a default with this source or of such a type (to fix, add
     //   a check for it in MacroClass#forceDefaultToNone).
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     for (RuleClass ruleClass : getBuiltinRuleClasses(false)) {
       if (ruleClass.getAttributes().isEmpty()) {
         continue;
@@ -1771,6 +1799,7 @@ def _impl(name, visibility, **kwargs):
 
   @Test
   public void inheritAttrs_fromExportedStarlarkRule() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/my_rule.bzl",
         """
@@ -1813,6 +1842,7 @@ def _my_macro_impl(name, visibility, **kwargs):
 
   @Test
   public void inheritAttrs_fromUnexportedStarlarkRule() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/my_macro.bzl",
         """
@@ -1850,6 +1880,7 @@ def _my_macro_impl(name, visibility, **kwargs):
 
   @Test
   public void inheritAttrs_fromExportedMacro() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/other_macro.bzl",
         """
@@ -1890,6 +1921,7 @@ def _my_macro_impl(name, visibility, **kwargs):
 
   @Test
   public void inheritAttrs_fromUnexportedMacro() throws Exception {
+    setBuildLanguageOptions("--experimental_enable_macro_inherit_attrs");
     scratch.file(
         "pkg/my_macro.bzl",
         """