Adds a new flag, --incompatible_enable_cc_test_feature which switches from the use of build variables to the feature of the same name.

RELNOTES:
Adds a new flag, `--incompatible_enable_cc_test_feature` which switches from the use of build variables to the feature of the same name.
PiperOrigin-RevId: 370905935

Author: Googler

src/main/java/com/google/devtools/build/lib/rules/cpp/CcBinary.java

@@ -15,6 +15,8 @@
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.devtools.build.lib.rules.cpp.CppRuleClasses.DYNAMIC_LINKING_MODE;
+import static com.google.devtools.build.lib.rules.cpp.CppRuleClasses.IS_CC_TEST_FEATURE_NAME;
+import static com.google.devtools.build.lib.rules.cpp.CppRuleClasses.LEGACY_IS_CC_TEST_FEATURE_NAME;
 import static com.google.devtools.build.lib.rules.cpp.CppRuleClasses.STATIC_LINKING_MODE;
 
 import com.google.auto.value.AutoValue;
@@ -378,13 +380,19 @@ public static void init(
     requestedFeaturesBuilder
         .addAll(ruleContext.getFeatures())
         .add(linkingMode == Link.LinkingMode.DYNAMIC ? DYNAMIC_LINKING_MODE : STATIC_LINKING_MODE);
+    ImmutableSet.Builder<String> disabledFeaturesBuilder = new ImmutableSet.Builder<>();
+    disabledFeaturesBuilder.addAll(ruleContext.getDisabledFeatures());
+    if (TargetUtils.isTestRule(ruleContext.getRule()) && cppConfiguration.useCcTestFeature()) {
+      requestedFeaturesBuilder.add(IS_CC_TEST_FEATURE_NAME);
+      disabledFeaturesBuilder.add(LEGACY_IS_CC_TEST_FEATURE_NAME);
+    }
 
     FdoContext fdoContext = common.getFdoContext();
     FeatureConfiguration featureConfiguration =
         CcCommon.configureFeaturesOrReportRuleError(
             ruleContext,
             requestedFeaturesBuilder.build(),
-            /* unsupportedFeatures= */ ruleContext.getDisabledFeatures(),
+            /* unsupportedFeatures= */ disabledFeaturesBuilder.build(),
             ccToolchain,
             semantics);
 

src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java

@@ -374,6 +374,10 @@ public boolean useArgsParamsFile() {
     return cppOptions.useArgsParamsFile;
   }
 
+  public boolean useCcTestFeature() {
+    return cppOptions.enableCcTestFeature;
+  }
+
   /** Returns whether or not to strip the binaries. */
   public boolean shouldStripBinaries() {
     return stripBinaries;

src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java

@@ -948,6 +948,20 @@ public Label getPropellerOptimizeLabel() {
               + " https://github.com/bazelbuild/bazel/issues/8706 for details.")
   public boolean disableNoCopts;
 
+  @Option(
+      name = "incompatible_enable_cc_test_feature",
+      defaultValue = "false",
+      documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
+      effectTags = {OptionEffectTag.ACTION_COMMAND_LINES},
+      metadataTags = {
+        OptionMetadataTag.INCOMPATIBLE_CHANGE,
+        OptionMetadataTag.TRIGGERED_BY_ALL_INCOMPATIBLE_CHANGES,
+      },
+      help =
+          "When enabled, it switches Crosstool to use feature 'is_cc_test' rather than"
+              + " the link-time build variable of the same name.")
+  public boolean enableCcTestFeature;
+
   @Option(
       name = "incompatible_load_cc_rules_from_bzl",
       defaultValue = "false",

src/main/java/com/google/devtools/build/lib/rules/cpp/CppRuleClasses.java

@@ -446,6 +446,17 @@ public static Label ccToolchainTypeAttribute(RuleDefinitionEnvironment env) {
    */
   public static final String NO_GENERATE_DEBUG_SYMBOLS_FEATURE_NAME = "no_generate_debug_symbols";
 
+  /**
+   * A feature which indicates that this target is a test (rather than a binary). This can be used
+   * to select test-only options.
+   */
+  public static final String IS_CC_TEST_FEATURE_NAME = "is_cc_test";
+
+  /**
+   * A feature which indicates whether we are using the legacy_is_cc_test build variable behavior.
+   */
+  public static final String LEGACY_IS_CC_TEST_FEATURE_NAME = "legacy_is_cc_test";
+
   /** Ancestor for all rules that do include scanning. */
   public static final class CcIncludeScanningRule implements RuleDefinition {
     @Override

src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java

@@ -142,10 +142,12 @@ public static CcToolchainVariables setupVariables(
       buildVariables.addStringVariable(IS_USING_FISSION.getVariableName(), "");
     }
 
-    if (useTestOnlyFlags) {
-      buildVariables.addIntegerVariable(IS_CC_TEST.getVariableName(), 1);
-    } else {
-      buildVariables.addIntegerVariable(IS_CC_TEST.getVariableName(), 0);
+    if (!cppConfiguration.useCcTestFeature()) {
+      if (useTestOnlyFlags) {
+        buildVariables.addIntegerVariable(IS_CC_TEST.getVariableName(), 1);
+      } else {
+        buildVariables.addIntegerVariable(IS_CC_TEST.getVariableName(), 0);
+      }
     }
 
     if (runtimeLibrarySearchDirectories != null) {

src/test/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariablesTest.java

@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.rules.cpp;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
@@ -24,6 +25,7 @@
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.util.AnalysisMock;
 import com.google.devtools.build.lib.packages.util.Crosstool.CcToolchainConfig;
+import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.ExpansionException;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainVariables.LibraryToLinkValue;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainVariables.VariableValue;
 import com.google.devtools.build.lib.rules.cpp.Link.LinkTargetType;
@@ -473,6 +475,35 @@ public void testIsCcTestLinkActionBuildVariable() throws Exception {
         .isFalse();
   }
 
+  @Test
+  public void testDisableIsCcTestLinkActionBuildVariable() throws Exception {
+    // The use of this feature (implied by the flag) replaces the use of the build variable.
+    // This test ensures the build variable is never *set*.
+    useConfiguration("--incompatible_enable_cc_test_feature");
+
+    scratch.file(
+        "x/BUILD",
+        "cc_test(name = 'foo_test', srcs = ['a.cc'])",
+        "cc_binary(name = 'foo', srcs = ['a.cc'])");
+    scratch.file("x/a.cc");
+
+    ConfiguredTarget testTarget = getConfiguredTarget("//x:foo_test");
+    CcToolchainVariables testVariables =
+        getLinkBuildVariables(testTarget, LinkTargetType.EXECUTABLE);
+
+    assertThrows(
+        ExpansionException.class,
+        () -> testVariables.getVariable(LinkBuildVariables.IS_CC_TEST.getVariableName()));
+
+    ConfiguredTarget binaryTarget = getConfiguredTarget("//x:foo");
+    CcToolchainVariables binaryVariables =
+        getLinkBuildVariables(binaryTarget, LinkTargetType.EXECUTABLE);
+
+    assertThrows(
+        ExpansionException.class,
+        () -> binaryVariables.getVariable(LinkBuildVariables.IS_CC_TEST.getVariableName()));
+  }
+
   @Test
   public void testStripBinariesIsEnabledWhenStripModeIsAlwaysNoMatterWhat() throws Exception {
     scratch.file("x/BUILD", "cc_binary(name = 'foo', srcs = ['a.cc'])");