Fix Label() behavior when called with '@repo' parts

The Label() constructor reads its repo mapping from BazelStarlarkContext, which is constructed when the thread is created. This is wrong because the repo mapping it needs is actually the one of the repo where the .bzl file lives. So we do that by having BazelModuleContext store the repo mapping (similar to how it stores the label right now) and return that. Callers who want the repo mapping (not just Label()) now get it from the topmost stack frame rather than from the BazelStarlarkContext, which no longer carries a repo mapping.

This coincidentally also fixes Label() behavior when called from a Bzlmod environment (either extension impl functions, or repo rules; see #13316), because we simply don't have a BazelStarlarkContext in those cases.

Fixes #12963.

PiperOrigin-RevId: 401732211

Author: Wyverald

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

@@ -44,7 +44,6 @@
 import com.google.devtools.build.lib.analysis.starlark.StarlarkModules;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
-import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.graph.Digraph;
 import com.google.devtools.build.lib.graph.Node;
 import com.google.devtools.build.lib.packages.BazelStarlarkContext;
@@ -860,13 +859,11 @@ public ImmutableMap<String, Object> getEnvironment() {
   }
 
   @Override
-  public void setStarlarkThreadContext(
-      StarlarkThread thread, Label fileLabel, RepositoryMapping repoMapping) {
+  public void setStarlarkThreadContext(StarlarkThread thread, Label fileLabel) {
     new BazelStarlarkContext(
             BazelStarlarkContext.Phase.LOADING,
             toolsRepository,
             configurationFragmentMap,
-            repoMapping,
             /*convertedLabelsInPackage=*/ new HashMap<>(),
             new SymbolGenerator<>(fileLabel),
             /*analysisRuleLabel=*/ null,

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

@@ -1127,7 +1127,6 @@ private StarlarkThread createStarlarkThread(Mutability mutability) {
             BazelStarlarkContext.Phase.ANALYSIS,
             ruleClassProvider.getToolsRepository(),
             /*fragmentNameToClass=*/ null,
-            getTarget().getPackage().getRepositoryMapping(),
             /*convertedLabelsInPackage=*/ new HashMap<>(),
             getSymbolGenerator(),
             getLabel(),

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

@@ -205,10 +205,10 @@ public static StarlarkDefinedConfigTransition newRegularTransition(
       StarlarkSemantics semantics,
       Label parentLabel,
       Location location,
-      BazelStarlarkContext starlarkContext)
+      RepositoryMapping repoMapping)
       throws EvalException {
     return new RegularTransition(
-        impl, inputs, outputs, semantics, parentLabel, location, starlarkContext.getRepoMapping());
+        impl, inputs, outputs, semantics, parentLabel, location, repoMapping);
   }
 
   public static StarlarkDefinedConfigTransition newAnalysisTestTransition(
@@ -350,7 +350,6 @@ public ImmutableMap<String, Map<String, Object>> evaluate(
                 Phase.ANALYSIS,
                 /*toolsRepository=*/ null,
                 /*fragmentNameToClass=*/ null,
-                repoMapping,
                 /*convertedLabelsInPackage=*/ new HashMap<>(),
                 dummySymbolGenerator,
                 parentLabel,

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

@@ -45,6 +45,7 @@
 import com.google.devtools.build.lib.starlarkbuildapi.StarlarkAttrModuleApi;
 import com.google.devtools.build.lib.util.FileType;
 import com.google.devtools.build.lib.util.FileTypeSet;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
@@ -137,13 +138,12 @@ private static Attribute.Builder<?> createAttribute(
       } else if (defaultValue instanceof StarlarkLateBoundDefault) {
         builder.value((StarlarkLateBoundDefault) defaultValue); // unchecked cast
       } else {
-        BazelStarlarkContext bazelStarlarkContext = BazelStarlarkContext.from(thread);
+        BazelModuleContext moduleContext =
+            BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread));
         builder.defaultValue(
             defaultValue,
             new BuildType.LabelConversionContext(
-                BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread)).label(),
-                bazelStarlarkContext.getRepoMapping(),
-                bazelStarlarkContext.getConvertedLabelsInPackage()),
+                moduleContext.label(), moduleContext.repoMapping(), new HashMap<>()),
             DEFAULT_ARG);
       }
     }

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

@@ -557,10 +557,12 @@ private static ImmutableList<Label> parseLabels(
       Iterable<String> inputs, StarlarkThread thread, String adjective) throws EvalException {
     ImmutableList.Builder<Label> parsedLabels = new ImmutableList.Builder<>();
     BazelStarlarkContext bazelStarlarkContext = BazelStarlarkContext.from(thread);
+    BazelModuleContext moduleContext =
+        BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread));
     LabelConversionContext context =
         new LabelConversionContext(
-            BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread)).label(),
-            bazelStarlarkContext.getRepoMapping(),
+            moduleContext.label(),
+            moduleContext.repoMapping(),
             bazelStarlarkContext.getConvertedLabelsInPackage());
     for (String input : inputs) {
       try {
@@ -958,8 +960,6 @@ public boolean isImmutable() {
 
   @Override
   public Label label(String labelString, StarlarkThread thread) throws EvalException {
-    BazelStarlarkContext context = BazelStarlarkContext.from(thread);
-
     // This function is surprisingly complex.
     //
     // - The logic to find the "current repo" is rather magical, using dynamic scope:
@@ -984,16 +984,14 @@ public Label label(String labelString, StarlarkThread thread) throws EvalExcepti
     //   and cache without needing four allocations (parseAbsoluteLabel,
     //   getRelativeWithRemapping, getUnambiguousCanonicalForm, parseAbsoluteLabel
     //   in labelCache)
-
-    // This is the label of the innermost BUILD/.bzl file on the current call stack.
-    Label parentLabel =
-        BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread)).label();
-
+    BazelModuleContext moduleContext =
+        BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread));
     try {
       LabelValidator.parseAbsoluteLabel(labelString);
       labelString =
-          parentLabel
-              .getRelativeWithRemapping(labelString, context.getRepoMapping())
+          moduleContext
+              .label()
+              .getRelativeWithRemapping(labelString, moduleContext.repoMapping())
               .getUnambiguousCanonicalForm();
       return labelCache.get(labelString);
     } catch (LabelValidator.BadLabelException | LabelSyntaxException e) {

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

@@ -89,11 +89,12 @@ private Label transformKey(StarlarkThread starlarkThread, Object key) throws Eva
     } else if (key instanceof String) {
       try {
         BazelStarlarkContext bazelStarlarkContext = BazelStarlarkContext.from(starlarkThread);
+        BazelModuleContext moduleContext =
+            BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(starlarkThread));
         LabelConversionContext context =
             new LabelConversionContext(
-                BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(starlarkThread))
-                    .label(),
-                bazelStarlarkContext.getRepoMapping(),
+                moduleContext.label(),
+                moduleContext.repoMapping(),
                 bazelStarlarkContext.getConvertedLabelsInPackage());
         return context.convert((String) key);
       } catch (LabelSyntaxException e) {

src/main/java/com/google/devtools/build/lib/bazel/repository/starlark/StarlarkRepositoryFunction.java

@@ -158,7 +158,6 @@ public RepositoryDirectoryValue.Builder fetch(
               BazelStarlarkContext.Phase.LOADING, // ("fetch")
               /*toolsRepository=*/ null,
               /*fragmentNameToClass=*/ null,
-              rule.getPackage().getRepositoryMapping(),
               /*convertedLabelsInPackage=*/ new HashMap<>(),
               new SymbolGenerator<>(key),
               /*analysisRuleLabel=*/ null,

src/main/java/com/google/devtools/build/lib/cmdline/Label.java

@@ -548,17 +548,19 @@ public Label getLocalTargetLabel(String targetName) throws LabelSyntaxException
       useStarlarkThread = true)
   public Label getRelative(String relName, StarlarkThread thread) throws LabelSyntaxException {
     HasRepoMapping hrm = thread.getThreadLocal(HasRepoMapping.class);
-    return getRelativeWithRemapping(relName, hrm.getRepoMapping());
+    return getRelativeWithRemapping(relName, hrm.getRepoMappingForCurrentBzlFile(thread));
   }
 
   /**
-   * An interface for retrieving a repository mapping.
+   * An interface for retrieving a repository mapping that's applicable for the repo containing the
+   * current .bzl file (more precisely, the .bzl file where the function at the innermost Starlark
+   * stack frame lives).
    *
    * <p>This has only a single implementation, {@code BazelStarlarkContext}, but we can't mention
    * that type here because logically it belongs in Bazel, above this package.
    */
   public interface HasRepoMapping {
-    RepositoryMapping getRepoMapping();
+    RepositoryMapping getRepoMappingForCurrentBzlFile(StarlarkThread thread);
   }
 
   /**

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

@@ -17,6 +17,7 @@
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import net.starlark.java.eval.Module;
 
 /**
@@ -28,6 +29,9 @@ public abstract class BazelModuleContext {
   /** Label associated with the Starlark {@link net.starlark.java.eval.Module}. */
   public abstract Label label();
 
+  /** The repository mapping applicable to the repo where the .bzl file is located in. */
+  public abstract RepositoryMapping repoMapping();
+
   /** Returns the name of the module's .bzl file, as provided to the parser. */
   public abstract String filename();
 
@@ -64,9 +68,11 @@ public static BazelModuleContext of(Module m) {
 
   public static BazelModuleContext create(
       Label label,
+      RepositoryMapping repoMapping,
       String filename,
       ImmutableMap<String, Module> loads,
       byte[] bzlTransitiveDigest) {
-    return new AutoValue_BazelModuleContext(label, filename, loads, bzlTransitiveDigest);
+    return new AutoValue_BazelModuleContext(
+        label, repoMapping, filename, loads, bzlTransitiveDigest);
   }
 }

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

@@ -25,6 +25,7 @@
 import java.util.Optional;
 import javax.annotation.Nullable;
 import net.starlark.java.eval.EvalException;
+import net.starlark.java.eval.Module;
 import net.starlark.java.eval.Starlark;
 import net.starlark.java.eval.StarlarkThread;
 
@@ -63,7 +64,6 @@ public void storeInThread(StarlarkThread thread) {
   @Nullable private final String toolsRepository;
   // Only necessary for loading phase threads to construct configuration_field.
   @Nullable private final ImmutableMap<String, Class<?>> fragmentNameToClass;
-  private final RepositoryMapping repoMapping;
   private final HashMap<String, Label> convertedLabelsInPackage;
   private final SymbolGenerator<?> symbolGenerator;
   @Nullable private final Label analysisRuleLabel;
@@ -77,7 +77,6 @@ public void storeInThread(StarlarkThread thread) {
    * @param fragmentNameToClass a map from configuration fragment name to configuration fragment
    *     class, such as "apple" to AppleConfiguration.class for loading phase threads, null for
    *     other threads.
-   * @param repoMapping a map from RepositoryName to RepositoryName to be used for external
    * @param convertedLabelsInPackage a mutable map from String to Label, used during package loading
    *     of a single package.
    * @param symbolGenerator a {@link SymbolGenerator} to be used when creating objects to be
@@ -90,22 +89,19 @@ public void storeInThread(StarlarkThread thread) {
   // separate structs, exactly one of which is populated (plus the common fields). And eliminate
   // StarlarkUtils.Phase.
   // TODO(adonovan): move PackageFactory.PackageContext in here, for loading-phase threads.
-  // TODO(adonovan): add a PackageIdentifier here, for use by the Starlark Label function.
   // TODO(adonovan): is there any reason not to put the entire RuleContext in this thread, for
   // analysis threads?
   public BazelStarlarkContext(
       Phase phase,
       @Nullable String toolsRepository,
       @Nullable ImmutableMap<String, Class<?>> fragmentNameToClass,
-      RepositoryMapping repoMapping,
       HashMap<String, Label> convertedLabelsInPackage,
       SymbolGenerator<?> symbolGenerator,
       @Nullable Label analysisRuleLabel,
       @Nullable Label networkAllowlistForTests) {
     this.phase = Preconditions.checkNotNull(phase);
     this.toolsRepository = toolsRepository;
     this.fragmentNameToClass = fragmentNameToClass;
-    this.repoMapping = repoMapping;
     this.convertedLabelsInPackage = convertedLabelsInPackage;
     this.symbolGenerator = Preconditions.checkNotNull(symbolGenerator);
     this.analysisRuleLabel = analysisRuleLabel;
@@ -130,8 +126,11 @@ public ImmutableMap<String, Class<?>> getFragmentNameToClass() {
    * in the BUILD files and the values are new repository names chosen by the main repository.
    */
   @Override
-  public RepositoryMapping getRepoMapping() {
-    return repoMapping;
+  public RepositoryMapping getRepoMappingForCurrentBzlFile(StarlarkThread thread) {
+    // TODO(b/200024947): Find a better place for this. We don't want Label to have to depend on
+    //   StarlarkModuleContext, but having the logic in BazelStarlarkContext is purely a historical
+    //   misstep.
+    return BazelModuleContext.of(Module.ofInnermostEnclosingStarlarkFunction(thread)).repoMapping();
   }
 
   /**