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

We still have open questions about how macro attribute inheritance ought to
interact with the tracking of whether rule attributes were or were not
explicitly provided.

In effect, this re-opens #24066
Part of addressing #24319

RELNOTES: symbolic macro attribute inheritance is now marked experimental; set --experimental_enable_macro_inherit_attrs flag to enable it.
PiperOrigin-RevId: 696582223
Change-Id: I3d7cb434bf8fe2da9cd10019e6075990205e7153

Author: tetromino

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",
@@ -857,6 +867,7 @@ 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)
@@ -972,6 +983,8 @@ 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

@@ -264,6 +264,8 @@ 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",
         """