Remove the unused concept of exec group inheritance

src/main/java/com/google/devtools/build/lib/analysis/ExecGroupCollection.java

@@ -15,7 +15,6 @@
 
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.devtools.build.lib.packages.ExecGroup.DEFAULT_EXEC_GROUP_NAME;
-import static java.util.stream.Collectors.joining;
 
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.HashBasedTable;
@@ -48,8 +47,7 @@ public abstract class ExecGroupCollection {
   /**
    * Prepares the input exec groups to serve as {@link Builder#execGroups}.
    *
-   * <p>Applies any inheritance specified via {@link ExecGroup#copyFrom} and adds auto exec groups
-   * when {@code useAutoExecGroups} is true.
+   * <p>Adds auto exec groups when {@code useAutoExecGroups} is true.
    */
   public static ImmutableMap<String, ExecGroup> process(
       ImmutableMap<String, ExecGroup> execGroups,
@@ -65,16 +63,12 @@ public static ImmutableMap<String, ExecGroup> process(
       String name = entry.getKey();
       ExecGroup execGroup = entry.getValue();
 
-      if (execGroup.copyFrom() != null) {
-        if (execGroup.copyFrom().equals(DEFAULT_EXEC_GROUP_NAME)) {
+      if (execGroup.copyFromDefault()) {
           execGroup =
               ExecGroup.builder()
                   .execCompatibleWith(defaultExecWith)
                   .toolchainTypes(defaultToolchainTypes)
                   .build();
-        } else {
-          execGroup = execGroup.inheritFrom(execGroups.get(execGroup.copyFrom()));
-        }
       }
 
       processedGroups.put(name, execGroup);
@@ -87,7 +81,6 @@ public static ImmutableMap<String, ExecGroup> process(
             toolchainType.toolchainType().toString(),
             ExecGroup.builder()
                 .addToolchainType(toolchainType)
-                .copyFrom(null)
                 .execCompatibleWith(defaultExecWith)
                 .build());
       }
@@ -268,7 +261,7 @@ public InvalidExecGroupException(Collection<String> invalidNames) {
       super(
           String.format(
               "Tried to set properties for non-existent exec groups: %s.",
-              invalidNames.stream().collect(joining(","))));
+              String.join(",", invalidNames)));
     }
 
     @Override

src/main/java/com/google/devtools/build/lib/analysis/starlark/StarlarkRuleClassFunctions.java

@@ -602,9 +602,10 @@ public StarlarkRuleFunction rule(
   /**
    * Returns a new callable representing a Starlark-defined rule.
    *
-   * <p>This is public for the benefit of {@link StarlarkTestingModule}, which has the unusual use
-   * case of creating new rule types to house analysis-time test assertions ({@code analysis_test}).
-   * It's probably not a good idea to add new callers of this method.
+   * <p>This is public for the benefit of {@link
+   * com.google.devtools.build.lib.rules.test.StarlarkTestingModule}, which has the unusual use case
+   * of creating new rule types to house analysis-time test assertions ({@code analysis_test}). It's
+   * probably not a good idea to add new callers of this method.
    *
    * <p>Note that the bzlFile and transitiveDigest params correspond to the outermost .bzl file
    * being evaluated, not the one in which rule() is called.
@@ -1989,7 +1990,6 @@ public ExecGroup execGroup(
     return ExecGroup.builder()
         .toolchainTypes(toolchainTypes)
         .execCompatibleWith(constraints)
-        .copyFrom(null)
         .build();
   }
 

src/main/java/com/google/devtools/build/lib/packages/ExecGroup.java

@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.packages;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static java.util.Objects.requireNonNull;
 
 import com.google.auto.value.AutoBuilder;
@@ -31,35 +32,37 @@
  *
  * @param toolchainTypesMap Returns the underlying map from label to ToolchainTypeRequirement.
  * @param execCompatibleWith Returns the execution constraints for this exec group.
- * @param copyFrom Returns the name of another exec group in the same rule to copy data from.
+ * @param copyFromDefault Whether this exec group should copy the data from the default exec group
+ *     in the same rule.
  */
 @AutoCodec
 public record ExecGroup(
     ImmutableMap<Label, ToolchainTypeRequirement> toolchainTypesMap,
     ImmutableSet<Label> execCompatibleWith,
-    @Nullable String copyFrom)
+    boolean copyFromDefault)
     implements ExecGroupApi {
   public ExecGroup {
     requireNonNull(toolchainTypesMap, "toolchainTypesMap");
     requireNonNull(execCompatibleWith, "execCompatibleWith");
+    checkArgument(
+        !copyFromDefault || (toolchainTypesMap.isEmpty() && execCompatibleWith.isEmpty()));
   }
 
   // This is intentionally a string that would fail {@code Identifier.isValid} so that
   // users can't create a group with the same name.
   public static final String DEFAULT_EXEC_GROUP_NAME = "default-exec-group";
 
+  /** An exec group that copies all data from the default exec group. */
+  public static final ExecGroup COPY_FROM_DEFAULT = builder().copyFromDefault(true).build();
+
   /** Returns a builder for a new ExecGroup. */
   public static Builder builder() {
     return new AutoBuilder_ExecGroup_Builder()
+        .copyFromDefault(false)
         .toolchainTypes(ImmutableSet.of())
         .execCompatibleWith(ImmutableSet.of());
   }
 
-  /** Create an exec group that inherits from the default exec group. */
-  public static ExecGroup copyFromDefault() {
-    return builder().copyFrom(DEFAULT_EXEC_GROUP_NAME).build();
-  }
-
   /** Returns the required toolchain types for this exec group. */
   public ImmutableSet<ToolchainTypeRequirement> toolchainTypes() {
     return ImmutableSet.copyOf(toolchainTypesMap().values());
@@ -70,21 +73,6 @@ public ToolchainTypeRequirement toolchainType(Label label) {
     return toolchainTypesMap().get(label);
   }
 
-  /** Creates a new exec group that inherits from the given group and this group. */
-  public ExecGroup inheritFrom(ExecGroup other) {
-    Builder builder = builder().copyFrom(null);
-    builder.toolchainTypesMapBuilder().putAll(this.toolchainTypesMap());
-    builder.toolchainTypesMapBuilder().putAll(other.toolchainTypesMap());
-
-    builder.execCompatibleWith(
-        new ImmutableSet.Builder<Label>()
-            .addAll(this.execCompatibleWith())
-            .addAll(other.execCompatibleWith())
-            .build());
-
-    return builder.build();
-  }
-
   /** A builder interface to create ExecGroup instances. */
   @AutoBuilder
   public interface Builder {
@@ -108,8 +96,8 @@ default Builder addToolchainType(ToolchainTypeRequirement toolchainTypeRequireme
     /** Sets the execution constraints. */
     Builder execCompatibleWith(ImmutableSet<Label> execCompatibleWith);
 
-    /** Sets the name of another exec group in the same rule to copy from. */
-    Builder copyFrom(@Nullable String copyfrom);
+    /** Do not call, internal usage only. */
+    Builder copyFromDefault(boolean copyFromDefault);
 
     /** Returns the new ExecGroup instance. */
     ExecGroup build();

src/main/java/com/google/devtools/build/lib/packages/RuleClass.java

@@ -1624,7 +1624,7 @@ public Builder addExecGroups(Map<String, ExecGroup> execGroups) {
 
     /** Adds an exec group that copies its toolchains and constraints from the rule. */
     public Builder addExecGroup(String name) {
-      return addExecGroups(ImmutableMap.of(name, ExecGroup.copyFromDefault()));
+      return addExecGroups(ImmutableMap.of(name, ExecGroup.COPY_FROM_DEFAULT));
     }
 
     /** An error to help report {@link ExecGroup}s with the same name */

src/test/java/com/google/devtools/build/lib/packages/RuleClassBuilderTest.java

@@ -205,13 +205,11 @@ public void testExecGroupsAreInherited() throws Exception {
         ExecGroup.builder()
             .addToolchainType(ToolchainTypeRequirement.create(mockToolchainType))
             .execCompatibleWith(ImmutableSet.of(mockConstraint))
-            .copyFrom(null)
             .build();
     ExecGroup childGroup =
         ExecGroup.builder()
             .toolchainTypes(ImmutableSet.of())
             .execCompatibleWith(ImmutableSet.of())
-            .copyFrom(null)
             .build();
     RuleClass parent =
         new RuleClass.Builder("$parent", RuleClassType.ABSTRACT, false)
@@ -233,15 +231,15 @@ public void testDuplicateExecGroupsThatInheritFromRuleIsOk() throws Exception {
     RuleClass a =
         new RuleClass.Builder("ruleA", RuleClassType.NORMAL, false)
             .factory(DUMMY_CONFIGURED_TARGET_FACTORY)
-            .addExecGroups(ImmutableMap.of("blueberry", ExecGroup.copyFromDefault()))
+            .addExecGroups(ImmutableMap.of("blueberry", ExecGroup.COPY_FROM_DEFAULT))
             .add(attr("tags", STRING_LIST))
             .addToolchainTypes(
                 ToolchainTypeRequirement.create(Label.parseCanonicalUnchecked("//some/toolchain")))
             .build();
     RuleClass b =
         new RuleClass.Builder("ruleB", RuleClassType.NORMAL, false)
             .factory(DUMMY_CONFIGURED_TARGET_FACTORY)
-            .addExecGroups(ImmutableMap.of("blueberry", ExecGroup.copyFromDefault()))
+            .addExecGroups(ImmutableMap.of("blueberry", ExecGroup.COPY_FROM_DEFAULT))
             .add(attr("tags", STRING_LIST))
             .addToolchainTypes(
                 ToolchainTypeRequirement.create(
@@ -271,7 +269,6 @@ public void testDuplicateExecGroupsThrowsError() throws Exception {
                             ToolchainTypeRequirement.create(
                                 Label.parseCanonicalUnchecked("//some/toolchain")))
                         .execCompatibleWith(ImmutableSet.of())
-                        .copyFrom(null)
                         .build()))
             .add(attr("tags", STRING_LIST))
             .build();
@@ -284,7 +281,6 @@ public void testDuplicateExecGroupsThrowsError() throws Exception {
                     ExecGroup.builder()
                         .toolchainTypes(ImmutableSet.of())
                         .execCompatibleWith(ImmutableSet.of())
-                        .copyFrom(null)
                         .build()))
             .add(attr("tags", STRING_LIST))
             .build();

src/test/java/com/google/devtools/build/lib/packages/RuleClassTest.java

@@ -1206,7 +1206,6 @@ public void testExecGroups() {
             ExecGroup.builder()
                 .addToolchainType(ToolchainTypeRequirement.create(toolchain))
                 .execCompatibleWith(ImmutableSet.of(constraint))
-                .copyFrom(null)
                 .build()));
 
     RuleClass ruleClass = ruleClassBuilder.build();