Create --incompatible_enable_late_bound_option_defaults flag

Equivalent to --experimental_use_late_bound_option_defaults, with a name that conforms to the policy for incompatible changes.

RELNOTES: None.
PiperOrigin-RevId: 210714389

src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java

@@ -855,6 +855,23 @@ public enum ConfigsMode {
                 + "removal of late bound option defaults.")
     public boolean useLateBoundOptionDefaults;
 
+    @Option(
+        name = "incompatible_enable_late_bound_option_defaults",
+        defaultValue = "true",
+        documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
+        effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS, OptionEffectTag.AFFECTS_OUTPUTS},
+        metadataTags = {
+          OptionMetadataTag.INCOMPATIBLE_CHANGE,
+          OptionMetadataTag.TRIGGERED_BY_ALL_INCOMPATIBLE_CHANGES
+        },
+        help =
+            "When false, Bazel will not allow late bound values read from the CROSSTOOL file "
+                + "to be used in config_settings. The CROSSTOOL field used in this manner is "
+                + "'compiler'. Instead of config_setting(values = {'compiler': 'x'}), "
+                + "config_setting(flag_values = {'@bazel_tools/tools/cpp:compiler': 'x'}) should "
+                + "be used.")
+    public boolean incompatibleEnableLateBoundOptionDefaults;
+
     /**
      * Converter for --experimental_dynamic_configs.
      */
@@ -1254,7 +1271,11 @@ public BuildConfiguration(
     this.testTimeout = ImmutableMap.copyOf(options.testTimeout);
 
     this.transitiveOptionDetails =
-        computeOptionsMap(buildOptions, fragments.values(), options.useLateBoundOptionDefaults);
+        computeOptionsMap(
+            buildOptions,
+            fragments.values(),
+            (options.useLateBoundOptionDefaults
+                && options.incompatibleEnableLateBoundOptionDefaults));
 
     ImmutableMap.Builder<String, String> globalMakeEnvBuilder = ImmutableMap.builder();
     for (Fragment fragment : fragments.values()) {

src/test/java/com/google/devtools/build/lib/rules/config/ConfigSettingTest.java

@@ -273,6 +273,18 @@ public void disallowLateBoundOptionDefaults() throws Exception {
     assertThat(getConfigMatchingProvider("//test:match").matches()).isFalse();
   }
 
+  /** Tests disallowing {@link BuildConfiguration.Fragment#lateBoundOptionDefaults} */
+  @Test
+  public void disallowLateBoundOptionDefaultsIncompatible() throws Exception {
+    useConfiguration("--incompatible_enable_late_bound_option_defaults=false");
+    scratch.file(
+        "test/BUILD",
+        "config_setting(",
+        "    name = 'match',",
+        "    values = { 'opt_with_default': 'overridden' }",
+        ")");
+    assertThat(getConfigMatchingProvider("//test:match").matches()).isFalse();
+  }
   /**
    * Tests matching on multi-value attributes with key=value entries (e.g. --define).
    */