Add Label.to_display_name()

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/dependency/DependencyModule.java

@@ -351,11 +351,22 @@ public String get(Iterable<JarOwner> missing, String recipient) {
         if (missingTargets.isEmpty()) {
           return "";
         }
+        String buildozerCommand = "";
+        // buildozer can't modify BUILD files in external repositories.
+        if (!recipient.startsWith("@")) {
+          buildozerCommand =
+              String.format(
+                  "%1$s ** You can use the following buildozer command:%2$s "
+                      + "\nbuildozer 'add deps %3$s' %4$s \n",
+                  "\033[35m\033[1m", "\033[0m", Joiner.on(" ").join(missingTargets), recipient);
+        }
         return String.format(
-            "%1$s ** Please add the following dependencies:%2$s \n  %3$s to %4$s \n"
-                + "%1$s ** You can use the following buildozer command:%2$s "
-                + "\nbuildozer 'add deps %3$s' %4$s \n\n",
-            "\033[35m\033[1m", "\033[0m", Joiner.on(" ").join(missingTargets), recipient);
+            "%1$s ** Please add the following dependencies:%2$s \n  %3$s to %4$s \n%5$s\n",
+            "\033[35m\033[1m",
+            "\033[0m",
+            Joiner.on(" ").join(missingTargets),
+            recipient,
+            buildozerCommand);
       }
     }
 

src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java

@@ -373,13 +373,9 @@ private String getProgressMessageChecked(@Nullable RepositoryMapping mainReposit
   private String replaceProgressMessagePlaceholders(
       String progressMessage, @Nullable RepositoryMapping mainRepositoryMapping) {
     if (progressMessage.contains("%{label}") && owner.getLabel() != null) {
-      String labelString;
-      if (mainRepositoryMapping != null) {
-        labelString = owner.getLabel().getDisplayForm(mainRepositoryMapping);
-      } else {
-        labelString = owner.getLabel().toString();
-      }
-      progressMessage = progressMessage.replace("%{label}", labelString);
+      progressMessage =
+          progressMessage.replace(
+              "%{label}", owner.getLabel().getDisplayForm(mainRepositoryMapping));
     }
     if (progressMessage.contains("%{output}") && getPrimaryOutput() != null) {
       progressMessage =

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

@@ -25,6 +25,7 @@
 import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
 import com.google.devtools.build.lib.analysis.config.BuildConfigurationValue;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.events.ExtendedEventHandler;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.skyframe.SkyFunction;
@@ -166,4 +167,10 @@ Artifact.DerivedArtifact getDerivedArtifact(
   ImmutableSet<Artifact> getTreeArtifactsConflictingWithFiles();
 
   ActionKeyContext getActionKeyContext();
+
+  /**
+   * The repository mapping applicable to the main repository. This is purely meant to support
+   * {@link com.google.devtools.build.lib.cmdline.Label#getDisplayForm)}.
+   */
+  RepositoryMapping getMainRepoMapping();
 }

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

@@ -27,6 +27,7 @@
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.events.ExtendedEventHandler;
 import com.google.devtools.build.lib.events.StoredEventHandler;
 import com.google.devtools.build.lib.packages.Target;
@@ -84,6 +85,8 @@ public final class CachingAnalysisEnvironment implements AnalysisEnvironment {
    */
   private final List<ActionAnalysisMetadata> actions = new ArrayList<>();
 
+  private final RepositoryMapping mainRepoMapping;
+
   public CachingAnalysisEnvironment(
       ArtifactFactory artifactFactory,
       ActionKeyContext actionKeyContext,
@@ -92,7 +95,8 @@ public CachingAnalysisEnvironment(
       boolean allowAnalysisFailures,
       ExtendedEventHandler errorEventListener,
       SkyFunction.Environment env,
-      StarlarkBuiltinsValue starlarkBuiltinsValue) {
+      StarlarkBuiltinsValue starlarkBuiltinsValue,
+      RepositoryMapping mainRepoMapping) {
     this.artifactFactory = artifactFactory;
     this.actionKeyContext = actionKeyContext;
     this.owner = Preconditions.checkNotNull(owner);
@@ -101,6 +105,7 @@ public CachingAnalysisEnvironment(
     this.errorEventListener = errorEventListener;
     this.skyframeEnv = env;
     this.starlarkBuiltinsValue = starlarkBuiltinsValue;
+    this.mainRepoMapping = mainRepoMapping;
     middlemanFactory = new MiddlemanFactory(artifactFactory, this);
   }
 
@@ -227,6 +232,11 @@ public ActionKeyContext getActionKeyContext() {
     return actionKeyContext;
   }
 
+  @Override
+  public RepositoryMapping getMainRepoMapping() {
+    return mainRepoMapping;
+  }
+
   @Override
   public boolean hasErrors() {
     Preconditions.checkState(enabled);

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

@@ -54,6 +54,7 @@
 import com.google.devtools.build.lib.analysis.starlark.StarlarkRuleContext;
 import com.google.devtools.build.lib.analysis.stringtemplate.TemplateContext;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.collect.ImmutableSortedKeyListMultimap;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
@@ -375,6 +376,11 @@ public String getWorkspaceName() {
     return rule.getPackage().getWorkspaceName();
   }
 
+  /** Returns the repository mapping of the main repository. */
+  public RepositoryMapping getMainRepoMapping() {
+    return getAnalysisEnvironment().getMainRepoMapping();
+  }
+
   /** The configuration conditions that trigger this rule's configurable attributes. */
   public ImmutableMap<Label, ConfigMatchingProvider> getConfigConditions() {
     return configConditions;

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

@@ -44,6 +44,13 @@ public abstract class BazelModuleContext {
   /** The repository mapping applicable to the repo where the .bzl file is located in. */
   public abstract RepositoryMapping repoMapping();
 
+  /**
+   * The repository mapping applicable to the main repository, possibly without WORKSPACE repos or
+   * null. This is purely meant to support {@link Label#getDisplayFormForStarlark(StarlarkThread)}.
+   */
+  @Nullable
+  public abstract RepositoryMapping bestEffortMainRepoMapping();
+
   /** Returns the name of the module's .bzl file, as provided to the parser. */
   public abstract String filename();
 
@@ -160,11 +167,12 @@ public static BazelModuleContext ofInnermostBzlOrFail(StarlarkThread thread, Str
   public static BazelModuleContext create(
       Label label,
       RepositoryMapping repoMapping,
+      @Nullable RepositoryMapping bestEffortMainRepoMapping,
       String filename,
       ImmutableList<Module> loads,
       byte[] bzlTransitiveDigest) {
     return new AutoValue_BazelModuleContext(
-        label, repoMapping, filename, loads, bzlTransitiveDigest);
+        label, repoMapping, bestEffortMainRepoMapping, filename, loads, bzlTransitiveDigest);
   }
 
   public final Label.PackageContext packageContext() {

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

@@ -438,10 +438,28 @@ public String getUnambiguousCanonicalForm() {
    * @param mainRepositoryMapping the {@link RepositoryMapping} of the main repository
    * @return analogous to {@link PackageIdentifier#getDisplayForm(RepositoryMapping)}
    */
-  public String getDisplayForm(RepositoryMapping mainRepositoryMapping) {
+  public String getDisplayForm(@Nullable RepositoryMapping mainRepositoryMapping) {
     return packageIdentifier.getDisplayForm(mainRepositoryMapping) + ":" + name;
   }
 
+  @StarlarkMethod(
+      name = "to_display_form",
+      useStarlarkThread = true,
+      doc =
+          "Returns a string representation of this label that is optimized for human readability."
+              + " The exact form of the return value is explicitly unspecified and subject to"
+              + " change."
+              + " The following properties are guaranteed for a <code>Label</code> <code>l</code>:"
+              + "<ul>"
+              + "  <li><code>l.to_display_form()</code> has no repository part if and only if <code>l</code> references the main repository;</li>"
+              + "  <li><code>Label(l.to_display_form()) == l</code> if the call to <code>Label</code> occurs in the main repository.</li>"
+              + "</ul>")
+  public String getDisplayFormForStarlark(StarlarkThread starlarkThread) throws EvalException {
+    checkRepoVisibilityForStarlark("to_display_form");
+    return getDisplayForm(
+        BazelModuleContext.ofInnermostBzlOrThrow(starlarkThread).bestEffortMainRepoMapping());
+  }
+
   /**
    * Returns a shorthand label string that is suitable for display, i.e. in addition to simplifying
    * the repository part, labels of the form {@code [@repo]//foo/bar:bar} are simplified to the

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

@@ -24,6 +24,8 @@
 import com.google.devtools.build.skyframe.SkyFunctionName;
 import com.google.devtools.build.skyframe.SkyKey;
 import com.google.devtools.build.skyframe.SkyKey.SkyKeyInterner;
+
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -222,7 +224,7 @@ public String getUnambiguousCanonicalForm() {
    *       <dd>only with Bzlmod if the current package belongs to a repository that is not visible
    *           from the main module
    */
-  public String getDisplayForm(RepositoryMapping mainRepositoryMapping) {
+  public String getDisplayForm(@Nullable RepositoryMapping mainRepositoryMapping) {
     return repository.getDisplayForm(mainRepositoryMapping) + "//" + pkgName;
   }
 

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

@@ -247,20 +247,25 @@ public String getCanonicalForm() {
    *       <dt><code>@protobuf</code>
    *       <dd>if this repository is a WORKSPACE dependency and its <code>name</code> is "protobuf",
    *           or if this repository is a Bzlmod dependency of the main module and its apparent name
-   *           is "protobuf"
+   *           is "protobuf" (in both cases only if mainRepositoryMapping is not null)
    *       <dt><code>@@protobuf~3.19.2</code>
    *       <dd>only with Bzlmod, if this a repository that is not visible from the main module
    */
-  public String getDisplayForm(RepositoryMapping mainRepositoryMapping) {
+  public String getDisplayForm(@Nullable RepositoryMapping mainRepositoryMapping) {
     Preconditions.checkArgument(
-        mainRepositoryMapping.ownerRepo() == null || mainRepositoryMapping.ownerRepo().isMain());
+        mainRepositoryMapping == null
+            || mainRepositoryMapping.ownerRepo() == null
+            || mainRepositoryMapping.ownerRepo().isMain());
     if (!isVisible()) {
       return getNameWithAt();
     }
     if (isMain()) {
       // Packages in the main repository can always use repo-relative form.
       return "";
     }
+    if (mainRepositoryMapping == null) {
+      return getNameWithAt();
+    }
     if (!mainRepositoryMapping.usesStrictDeps()) {
       // If the main repository mapping is not using strict visibility, then Bzlmod is certainly
       // disabled, which means that canonical and apparent names can be used interchangeably from

src/main/java/com/google/devtools/build/lib/rules/java/JavaCompilationHelper.java

@@ -16,13 +16,16 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.devtools.build.lib.packages.ExecGroup.DEFAULT_EXEC_GROUP_NAME;
 
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.LoadingCache;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Interner;
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.CommandLineItem;
 import com.google.devtools.build.lib.actions.ExecutionRequirements;
 import com.google.devtools.build.lib.actions.ParamFileInfo;
 import com.google.devtools.build.lib.actions.ParameterFile;
@@ -38,6 +41,7 @@
 import com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode;
 import com.google.devtools.build.lib.analysis.test.InstrumentedFilesCollector;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.Order;
@@ -63,6 +67,31 @@
  */
 public final class JavaCompilationHelper {
 
+  /**
+   * Cache for the {@link com.google.devtools.build.lib.actions.CommandLineItem.MapFn} that turns a
+   * {@link Label} into its possibly @-prefixed display form, which requires the repository mapping
+   * of the main repo.
+   *
+   * <p>The capacity of this cache after weakly reachable object have been cleaned will always be 1
+   * as there is only a single main repo mapping in a given build.
+   */
+  static final LoadingCache<RepositoryMapping, CommandLineItem.ExceptionlessMapFn<Label>>
+      TARGET_LABEL_MAP_FN_CACHE =
+          Caffeine.newBuilder()
+              .initialCapacity(1)
+              .weakKeys()
+              .build(
+                  mainRepoMapping ->
+                      (label, args) -> {
+                        String displayForm = label.getDisplayForm(mainRepoMapping);
+                        if (displayForm.startsWith("@")) {
+                          // @-prefixed strings will be assumed to be filenames and expanded by
+                          // {@link JavaLibraryBuildRequest}, so add an extra &at; to escape it.
+                          args.accept("@" + displayForm);
+                        } else {
+                          args.accept(displayForm);
+                        }
+                      });
   private static final Interner<ImmutableList<String>> javacOptsInterner =
       BlazeInterners.newWeakInterner();
   private static final Interner<ImmutableMap<String, String>> executionInfoInterner =

src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilder.java

@@ -28,6 +28,7 @@
 import com.google.devtools.build.lib.actions.extra.JavaCompileInfo;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
+import com.google.devtools.build.lib.analysis.actions.CustomCommandLine.VectorArg;
 import com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
@@ -313,14 +314,12 @@ private CustomCommandLine buildParamFileContents(ImmutableList<String> javacOpts
       result.add("--");
     }
     if (targetLabel != null) {
-      result.add("--target_label");
-      if (targetLabel.getRepository().isMain()) {
-        result.addLabel(targetLabel);
-      } else {
-        // @-prefixed strings will be assumed to be filenames and expanded by
-        // {@link JavaLibraryBuildRequest}, so add an extra &at; to escape it.
-        result.addPrefixedLabel("@", targetLabel);
-      }
+      result.addAll(
+          "--target_label",
+          VectorArg.of(ImmutableList.of(targetLabel))
+              .mapped(
+                  JavaCompilationHelper.TARGET_LABEL_MAP_FN_CACHE.get(
+                      ruleContext.getMainRepoMapping())));
     }
     result.add("--injecting_rule_kind", injectingRuleKind);
     // strict_java_deps controls whether the mapping from jars to targets is

src/main/java/com/google/devtools/build/lib/rules/java/JavaHeaderCompileAction.java

@@ -40,6 +40,7 @@
 import com.google.devtools.build.lib.actions.SpawnResult;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
+import com.google.devtools.build.lib.analysis.actions.CustomCommandLine.VectorArg;
 import com.google.devtools.build.lib.analysis.actions.PathMappers;
 import com.google.devtools.build.lib.analysis.actions.SpawnAction;
 import com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode;
@@ -443,14 +444,12 @@ public void build(JavaToolchainProvider javaToolchain) throws RuleErrorException
       }
 
       if (targetLabel != null) {
-        commandLine.add("--target_label");
-        if (targetLabel.getRepository().isMain()) {
-          commandLine.addLabel(targetLabel);
-        } else {
-          // @-prefixed strings will be assumed to be params filenames and expanded,
-          // so add an extra @ to escape it.
-          commandLine.addPrefixedLabel("@", targetLabel);
-        }
+        commandLine.addAll(
+            "--target_label",
+            VectorArg.of(ImmutableList.of(targetLabel))
+                .mapped(
+                    JavaCompilationHelper.TARGET_LABEL_MAP_FN_CACHE.get(
+                        ruleContext.getMainRepoMapping())));
       }
 
       ImmutableMap<String, String> executionInfo =

src/main/java/com/google/devtools/build/lib/skyframe/AspectFunction.java

@@ -58,6 +58,8 @@
 import com.google.devtools.build.lib.causes.LabelCause;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.PackageIdentifier;
+import com.google.devtools.build.lib.cmdline.RepositoryMapping;
+import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.events.Event;
@@ -763,12 +765,23 @@ private AspectValue createAspect(
     if (env.valuesMissing()) {
       return null;
     }
+    RepositoryMappingValue mainRepoMappingValue =
+        (RepositoryMappingValue) env.getValue(RepositoryMappingValue.key(RepositoryName.MAIN));
+    if (mainRepoMappingValue == null) {
+      return null;
+    }
 
     SkyframeBuildView view = buildViewProvider.getSkyframeBuildView();
 
     StoredEventHandler events = new StoredEventHandler();
     CachingAnalysisEnvironment analysisEnvironment =
-        view.createAnalysisEnvironment(key, events, env, configuration, starlarkBuiltinsValue);
+        view.createAnalysisEnvironment(
+            key,
+            events,
+            env,
+            configuration,
+            starlarkBuiltinsValue,
+            mainRepoMappingValue.getRepositoryMapping());
 
     ConfiguredAspect configuredAspect;
     if (aspect.getDefinition().applyToGeneratingRules() && associatedTarget instanceof OutputFile) {