From 6586341e4f549de2e1458d96d983c807ef51e1f2 Mon Sep 17 00:00:00 2001
From: Fabian Meumertzheim <fabian@meumertzhe.im>
Date: Wed, 10 Apr 2024 22:35:00 +0200
Subject: [PATCH] Give `StarlarkValue#debugPrint` access to the
 `StarlarkThread`

Since `debugPrint` is meant for emitting potentially non-deterministic, it is safe to give it access to `StarlarkThread` information.

This will be used in a follow-up to let `print` and `fail` emit `Label`s in display form without having to track the reverse repo mapping for the sake of invalidation of repo rules or module extensions.

Work towards #20486
---
 .../build/lib/actions/AbstractAction.java     | 10 +---
 .../RuleConfiguredTarget.java                 |  4 +-
 .../build/lib/analysis/starlark/Args.java     |  2 +-
 .../bzlmod/BazelModuleResolutionValue.java    |  2 +-
 .../lib/bazel/bzlmod/ModuleFileValue.java     |  2 +-
 .../lib/bazel/bzlmod/TypeCheckedTag.java      |  4 +-
 .../build/lib/cmdline/BazelModuleContext.java | 10 +++-
 .../devtools/build/lib/cmdline/Label.java     | 13 +++-
 .../build/lib/cmdline/PackageIdentifier.java  |  3 +-
 .../build/lib/cmdline/RepositoryName.java     | 11 +++-
 .../build/lib/rules/cpp/CcLinkingContext.java | 12 ++--
 .../cpp/FeatureConfigurationForStarlark.java  |  2 +-
 .../build/lib/rules/cpp/LibraryToLink.java    |  3 +-
 .../google/devtools/build/lib/skyframe/BUILD  |  1 +
 .../build/lib/skyframe/BzlLoadFunction.java   | 34 +++++++++++
 .../lib/skyframe/BzlmodRepoCycleReporter.java | 28 ++++++++-
 .../net/starlark/java/eval/MethodLibrary.java |  6 +-
 .../java/net/starlark/java/eval/Printer.java  |  6 +-
 .../net/starlark/java/eval/StarlarkValue.java |  4 +-
 .../actions/BuildInfoFileWriteActionTest.java |  1 +
 .../devtools/build/lib/cmdline/LabelTest.java |  6 ++
 .../lib/cmdline/PackageIdentifierTest.java    |  2 +
 .../build/lib/cmdline/RepositoryNameTest.java | 17 ++++++
 .../lib/starlark/StarlarkIntegrationTest.java |  2 +-
 .../StarlarkRuleClassFunctionsTest.java       |  1 +
 ...arlarkRuleImplementationFunctionsTest.java |  9 ++-
 .../util/BazelEvaluationTestCase.java         |  1 +
 .../java/eval/StarlarkEvaluationTest.java     | 14 +++--
 src/test/py/bazel/bzlmod/bazel_module_test.py | 59 +++++++++++++++++++
 src/test/shell/bazel/platforms_test.sh        |  2 +-
 30 files changed, 222 insertions(+), 49 deletions(-)

diff --git a/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java b/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
index 60d2ccef5896a6..8694278b959743 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
@@ -368,13 +368,9 @@ 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 =
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/configuredtargets/RuleConfiguredTarget.java b/src/main/java/com/google/devtools/build/lib/analysis/configuredtargets/RuleConfiguredTarget.java
index d78f147c411862..43b9762492d263 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/configuredtargets/RuleConfiguredTarget.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/configuredtargets/RuleConfiguredTarget.java
@@ -54,7 +54,7 @@
 import net.starlark.java.eval.Dict;
 import net.starlark.java.eval.Printer;
 import net.starlark.java.eval.Starlark;
-import net.starlark.java.eval.StarlarkSemantics;
+import net.starlark.java.eval.StarlarkThread;
 
 /**
  * A {@link com.google.devtools.build.lib.analysis.ConfiguredTarget} that is produced by a rule.
@@ -249,7 +249,7 @@ public void repr(Printer printer) {
   }
 
   @Override
-  public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public void debugPrint(Printer printer, StarlarkThread thread) {
     // Show the names of the provider keys that this target propagates.
     // Provider key names might potentially be *private* information, and thus a comprehensive
     // list of provider keys should not be exposed in any way other than for debug information.
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/starlark/Args.java b/src/main/java/com/google/devtools/build/lib/analysis/starlark/Args.java
index cade026c9edd4b..b451eb528cddc9 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/starlark/Args.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/starlark/Args.java
@@ -71,7 +71,7 @@ public void repr(Printer printer) {
   }
 
   @Override
-  public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public void debugPrint(Printer printer, StarlarkThread thread) {
     try {
       printer.append(
           Joiner.on(" ").join(build(/* mainRepoMappingSupplier= */ () -> null).arguments()));
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelModuleResolutionValue.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelModuleResolutionValue.java
index 19c642cfa5d7f7..ca3794479605fe 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelModuleResolutionValue.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelModuleResolutionValue.java
@@ -27,7 +27,7 @@
  * graphs.
  */
 @AutoValue
-abstract class BazelModuleResolutionValue implements SkyValue {
+public abstract class BazelModuleResolutionValue implements SkyValue {
   /* TODO(andreisolo): Also load the modules overridden by {@code single_version_override} or
       NonRegistryOverride if we need to detect changes in the dependency graph caused by them.
   */
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileValue.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileValue.java
index 7c7e38fd6c3db6..4a9d4653cdc92b 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileValue.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileValue.java
@@ -99,7 +99,7 @@ public static Key key(ModuleKey moduleKey, @Nullable ModuleOverride override) {
   /** {@link SkyKey} for {@link ModuleFileValue} computation. */
   @AutoCodec
   @AutoValue
-  abstract static class Key implements SkyKey {
+  public abstract static class Key implements SkyKey {
     private static final SkyKeyInterner<Key> interner = SkyKey.newInterner();
 
     abstract ModuleKey getModuleKey();
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/TypeCheckedTag.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/TypeCheckedTag.java
index b9601be57ff8b9..e6d5c4eb21d16f 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/TypeCheckedTag.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/TypeCheckedTag.java
@@ -24,7 +24,7 @@
 import net.starlark.java.annot.StarlarkBuiltin;
 import net.starlark.java.eval.EvalException;
 import net.starlark.java.eval.Printer;
-import net.starlark.java.eval.StarlarkSemantics;
+import net.starlark.java.eval.StarlarkThread;
 import net.starlark.java.eval.Structure;
 import net.starlark.java.spelling.SpellChecker;
 import net.starlark.java.syntax.Location;
@@ -150,7 +150,7 @@ public String getErrorMessageForUnknownField(String field) {
   }
 
   @Override
-  public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public void debugPrint(Printer printer, StarlarkThread thread) {
     printer.append(String.format("'%s' tag at %s", tagClassName, location));
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/BazelModuleContext.java b/src/main/java/com/google/devtools/build/lib/cmdline/BazelModuleContext.java
index 9bd7dd45b30ef7..bb00dc332ef7e7 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/BazelModuleContext.java
+++ b/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. This is purely meant to support
+   * {@link Label#debugPrint}.
+   */
+  @Nullable
+  public abstract RepositoryMapping mainRepoMapping();
+
   /** 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 mainRepoMapping,
       String filename,
       ImmutableList<Module> loads,
       byte[] bzlTransitiveDigest) {
     return new AutoValue_BazelModuleContext(
-        label, repoMapping, filename, loads, bzlTransitiveDigest);
+        label, repoMapping, mainRepoMapping, filename, loads, bzlTransitiveDigest);
   }
 
   public final Label.PackageContext packageContext() {
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
index 3d2443802e1ff4..962f468888e8ce 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
@@ -66,7 +66,11 @@
         "A BUILD target identifier."
             + "<p>For every <code>Label</code> instance <code>l</code>, the string representation"
             + " <code>str(l)</code> has the property that <code>Label(str(l)) == l</code>,"
-            + " regardless of where the <code>Label()</code> call occurs.")
+            + " regardless of where the <code>Label()</code> call occurs."
+            + "<p>When passed as positional arguments to <code>print()</code> or <code>fail()"
+            + "</code>, <code>Label</code> use a string representation optimized for human readability"
+            + " instead. This representation uses an <a href=\"/external/overview#apparent-repo-name\">"
+            + "apparent repository name</a> from the perspective of the main repository if possible.")
 @Immutable
 @ThreadSafe
 public final class Label implements Comparable<Label>, StarlarkValue, SkyKey, CommandLineItem {
@@ -442,7 +446,7 @@ 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;
   }
 
@@ -655,6 +659,11 @@ public void repr(Printer printer) {
     printer.append(")");
   }
 
+  @Override
+  public void debugPrint(Printer printer, StarlarkThread thread) {
+    printer.append(getDisplayForm(BazelModuleContext.ofInnermostBzlOrThrow(thread).mainRepoMapping()));
+  }
+
   @Override
   public void str(Printer printer, StarlarkSemantics semantics) {
     if (getRepository().isMain()
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
index 4271d0d6706489..5611913f178202 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
@@ -24,6 +24,7 @@
 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;
 
 /**
@@ -226,7 +227,7 @@ 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;
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
index 3747008f2cc58a..d7435f7fb68251 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
@@ -249,13 +249,15 @@ 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();
     }
@@ -263,6 +265,9 @@ public String getDisplayForm(RepositoryMapping mainRepositoryMapping) {
       // 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
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkingContext.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkingContext.java
index 1794531b75b4d8..7ffeaddebec14f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkingContext.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkingContext.java
@@ -276,23 +276,23 @@ public Sequence<Linkstamp> getLinkstampsForStarlark() {
     }
 
     @Override
-    public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+    public void debugPrint(Printer printer, StarlarkThread thread) {
       printer.append("<LinkerInput(owner=");
       if (owner == null) {
         printer.append("[null owner, uses old create_linking_context API]");
       } else {
-        owner.debugPrint(printer, semantics);
+        owner.debugPrint(printer, thread);
       }
       printer.append(", libraries=[");
       for (LibraryToLink libraryToLink : libraries) {
-        libraryToLink.debugPrint(printer, semantics);
+        libraryToLink.debugPrint(printer, thread);
         printer.append(", ");
       }
       printer.append("], userLinkFlags=[");
       printer.append(Joiner.on(", ").join(userLinkFlags));
       printer.append("], nonCodeInputs=[");
       for (Artifact nonCodeInput : nonCodeInputs) {
-        nonCodeInput.debugPrint(printer, semantics);
+        nonCodeInput.debugPrint(printer, thread);
         printer.append(", ");
       }
       // TODO(cparsons): Add debug repesentation of linkstamps.
@@ -390,10 +390,10 @@ public String toString() {
   @Nullable private final ExtraLinkTimeLibraries extraLinkTimeLibraries;
 
   @Override
-  public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public void debugPrint(Printer printer, StarlarkThread thread) {
     printer.append("<CcLinkingContext([");
     for (LinkerInput linkerInput : linkerInputs.toList()) {
-      linkerInput.debugPrint(printer, semantics);
+      linkerInput.debugPrint(printer, thread);
       printer.append(", ");
     }
     printer.append("])>");
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/FeatureConfigurationForStarlark.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/FeatureConfigurationForStarlark.java
index d567e577eea472..485fd1c0b5f277 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/FeatureConfigurationForStarlark.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/FeatureConfigurationForStarlark.java
@@ -62,7 +62,7 @@ public void str(Printer printer, StarlarkSemantics semantics) {
   }
 
   @Override
-  public void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public void debugPrint(Printer printer, StarlarkThread thread) {
     printer.append("<FeatureConfiguration(");
     printer.append(Joiner.on(", ").join(featureConfiguration.getEnabledFeatureNames()));
     printer.append(")>");
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/LibraryToLink.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/LibraryToLink.java
index d97ebd2981a464..9cfa09fb5df786 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/LibraryToLink.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/LibraryToLink.java
@@ -31,7 +31,6 @@
 import net.starlark.java.eval.Printer;
 import net.starlark.java.eval.Sequence;
 import net.starlark.java.eval.StarlarkList;
-import net.starlark.java.eval.StarlarkSemantics;
 import net.starlark.java.eval.StarlarkThread;
 
 /** Encapsulates information for linking a library. */
@@ -224,7 +223,7 @@ LinkerInputs.LibraryToLink getInterfaceLibraryToLink() {
   abstract boolean getDisableWholeArchive();
 
   @Override
-  public final void debugPrint(Printer printer, StarlarkSemantics semantics) {
+  public final void debugPrint(Printer printer, StarlarkThread thread) {
     printer.append("<LibraryToLink(");
     printer.append(
         Joiner.on(", ")
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/BUILD b/src/main/java/com/google/devtools/build/lib/skyframe/BUILD
index 8f39bc03046532..bebd8d4dc1323e 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/BUILD
@@ -2587,6 +2587,7 @@ java_library(
         ":sky_functions",
         "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:module_extension",
         "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:repo_rule_value",
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:resolution",
         "//src/main/java/com/google/devtools/build/lib/cmdline",
         "//src/main/java/com/google/devtools/build/lib/events",
         "//src/main/java/com/google/devtools/build/lib/packages",
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/BzlLoadFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/BzlLoadFunction.java
index 7c17bf89f6927b..749aa813ba4760 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/BzlLoadFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/BzlLoadFunction.java
@@ -65,6 +65,7 @@
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
@@ -762,6 +763,11 @@ private BzlLoadValue computeInternalWithCompiledBzl(
     if (repoMapping == null) {
       return null;
     }
+    Optional<RepositoryMapping> mainRepoMapping =
+        getMainRepositoryMapping(key, builtins.starlarkSemantics, env);
+    if (mainRepoMapping == null) {
+      return null;
+    }
     Label.RepoMappingRecorder repoMappingRecorder = new Label.RepoMappingRecorder();
     ImmutableList<Pair<String, Location>> programLoads = getLoadsFromProgram(prog);
     ImmutableList<Label> loadLabels =
@@ -840,6 +846,7 @@ private BzlLoadValue computeInternalWithCompiledBzl(
         BazelModuleContext.create(
             label,
             repoMapping,
+            mainRepoMapping.orElse(null),
             prog.getFilename(),
             ImmutableList.copyOf(loadMap.values()),
             transitiveDigest);
@@ -972,6 +979,33 @@ private static RepositoryMapping getRepositoryMapping(
     return repositoryMappingValue.getRepositoryMapping();
   }
 
+  @Nullable
+  private static Optional<RepositoryMapping> getMainRepositoryMapping(
+      BzlLoadValue.Key key, StarlarkSemantics starlarkSemantics, Environment env)
+      throws InterruptedException {
+    if (!starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_BZLMOD)) {
+      return Optional.empty();
+    }
+    RepositoryMappingValue.Key repoMappingKey;
+    if (key instanceof BzlLoadValue.KeyForBuild) {
+      repoMappingKey = RepositoryMappingValue.key(RepositoryName.MAIN);
+    } else if ((key instanceof BzlLoadValue.KeyForBzlmod
+            && !(key instanceof BzlLoadValue.KeyForBzlmodBootstrap))
+        || key instanceof BzlLoadValue.KeyForWorkspace) {
+      // Since the main repo mapping requires evaluating WORKSPACE, but WORKSPACE can load from
+      // extension repos, requesting the full main repo mapping would cause a cycle.
+      repoMappingKey = RepositoryMappingValue.KEY_FOR_ROOT_MODULE_WITHOUT_WORKSPACE_REPOS;
+    } else {
+      // Builtins and Bzlmod bootstrap repo rules don't need the main repo mapping.
+      return Optional.empty();
+    }
+    var mainRepositoryMappingValue = (RepositoryMappingValue) env.getValue(repoMappingKey);
+    if (mainRepositoryMappingValue == null) {
+      return null;
+    }
+    return Optional.of(mainRepositoryMappingValue.getRepositoryMapping());
+  }
+
   /**
    * Validates a label appearing in a {@code load()} statement, throwing {@link
    * LabelSyntaxException} on failure.
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoCycleReporter.java b/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoCycleReporter.java
index d11de3b25d8ff5..b01cd663549295 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoCycleReporter.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoCycleReporter.java
@@ -20,8 +20,11 @@
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.bazel.bzlmod.BazelDepGraphValue;
+import com.google.devtools.build.lib.bazel.bzlmod.BazelModuleResolutionValue;
 import com.google.devtools.build.lib.bazel.bzlmod.BzlmodRepoRuleValue;
 import com.google.devtools.build.lib.bazel.bzlmod.ModuleExtensionId;
+import com.google.devtools.build.lib.bazel.bzlmod.ModuleFileValue;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.events.Event;
@@ -69,6 +72,15 @@ public class BzlmodRepoCycleReporter implements CyclesReporter.SingleCycleReport
   private static final Predicate<SkyKey> IS_WORKSPACE_FILE =
       SkyFunctions.isSkyFunction(WorkspaceFileValue.WORKSPACE_FILE);
 
+  private static final Predicate<SkyKey> IS_MODULE_RESOLUTION =
+      SkyFunctions.isSkyFunction(SkyFunctions.BAZEL_MODULE_RESOLUTION);
+
+  private static final Predicate<SkyKey> IS_DEP_GRAPH =
+      SkyFunctions.isSkyFunction(SkyFunctions.BAZEL_DEP_GRAPH);
+
+  private static final Predicate<SkyKey> IS_MODULE_FILE =
+      SkyFunctions.isSkyFunction(SkyFunctions.MODULE_FILE);
+
   private static void requestRepoDefinitions(
       ExtendedEventHandler eventHandler, Iterable<SkyKey> repos) {
     for (SkyKey repo : repos) {
@@ -113,7 +125,10 @@ public boolean maybeReportCycle(
                 IS_MODULE_EXTENSION_REPO_MAPPING_ENTRIES,
                 IS_PACKAGE,
                 IS_EXTERNAL_PACKAGE,
-                IS_WORKSPACE_FILE))
+                IS_WORKSPACE_FILE,
+                IS_MODULE_RESOLUTION,
+                IS_DEP_GRAPH,
+                IS_MODULE_FILE))
         && Iterables.any(cycle, Predicates.or(IS_REPO_RULE, IS_EXTENSION_IMPL))) {
       StringBuilder cycleMessage =
           new StringBuilder(
@@ -127,7 +142,10 @@ public boolean maybeReportCycle(
                   IS_EXTENSION_IMPL,
                   IS_BZL_LOAD,
                   IS_REPO_MAPPING,
-                  IS_WORKSPACE_FILE));
+                  IS_WORKSPACE_FILE,
+                  IS_MODULE_RESOLUTION,
+                  IS_DEP_GRAPH,
+                  IS_MODULE_FILE));
       Function<Object, String> printer =
           rawInput -> {
             SkyKey input = (SkyKey) rawInput;
@@ -144,6 +162,12 @@ public boolean maybeReportCycle(
               return String.format("repository mapping of %s", key.repoName());
             } else if (input.argument() instanceof WorkspaceFileValue.WorkspaceFileKey) {
               return "WORKSPACE file";
+            } else if (input.argument() == BazelModuleResolutionValue.KEY) {
+              return "module resolution";
+            } else if (input.argument() == BazelDepGraphValue.KEY) {
+              return "module dependency graph";
+            } else if (input.argument() instanceof ModuleFileValue.Key) {
+              return "module file of " + input.argument();
             } else {
               Preconditions.checkArgument(input.argument() instanceof BzlLoadValue.Key);
               return ((BzlLoadValue.Key) input.argument()).getLabel().toString();
diff --git a/src/main/java/net/starlark/java/eval/MethodLibrary.java b/src/main/java/net/starlark/java/eval/MethodLibrary.java
index 9e3f978bd8494c..b8d206ad1017ff 100644
--- a/src/main/java/net/starlark/java/eval/MethodLibrary.java
+++ b/src/main/java/net/starlark/java/eval/MethodLibrary.java
@@ -841,14 +841,14 @@ public void fail(Object msg, Object attr, String sep, Tuple args, StarlarkThread
       if (needSeparator) {
         printer.append(sep);
       }
-      printer.debugPrint(msg, thread.getSemantics());
+      printer.debugPrint(msg, thread);
       needSeparator = true;
     }
     for (Object arg : args) {
       if (needSeparator) {
         printer.append(sep);
       }
-      printer.debugPrint(arg, thread.getSemantics());
+      printer.debugPrint(arg, thread);
       needSeparator = true;
     }
     throw Starlark.errorf("%s", printer.toString());
@@ -882,7 +882,7 @@ public void print(String sep, Sequence<?> args, StarlarkThread thread) throws Ev
     String separator = "";
     for (Object x : args) {
       p.append(separator);
-      p.debugPrint(x, thread.getSemantics());
+      p.debugPrint(x, thread);
       separator = sep;
     }
     // The PRINT_TEST_MARKER key is used in tests to verify the effects of command-line options.
diff --git a/src/main/java/net/starlark/java/eval/Printer.java b/src/main/java/net/starlark/java/eval/Printer.java
index 1215f0ef3d5b80..8bfc4626e6fc22 100644
--- a/src/main/java/net/starlark/java/eval/Printer.java
+++ b/src/main/java/net/starlark/java/eval/Printer.java
@@ -114,13 +114,13 @@ public final String toString() {
    *
    * <p>Implementations of StarlarkValue may define their own behavior of {@code debugPrint}.
    */
-  public Printer debugPrint(Object o, StarlarkSemantics semantics) {
+  public Printer debugPrint(Object o, StarlarkThread thread) {
     if (o instanceof StarlarkValue) {
-      ((StarlarkValue) o).debugPrint(this, semantics);
+      ((StarlarkValue) o).debugPrint(this, thread);
       return this;
     }
 
-    return this.str(o, semantics);
+    return this.str(o, thread.getSemantics());
   }
 
   /**
diff --git a/src/main/java/net/starlark/java/eval/StarlarkValue.java b/src/main/java/net/starlark/java/eval/StarlarkValue.java
index 851626d634d32c..c4ae15ef762983 100644
--- a/src/main/java/net/starlark/java/eval/StarlarkValue.java
+++ b/src/main/java/net/starlark/java/eval/StarlarkValue.java
@@ -57,8 +57,8 @@ default void str(Printer printer, StarlarkSemantics semantics) {
    *
    * @param printer a printer to be used for formatting nested values.
    */
-  default void debugPrint(Printer printer, StarlarkSemantics semantics) {
-    str(printer, semantics);
+  default void debugPrint(Printer printer, StarlarkThread thread) {
+    str(printer, thread.getSemantics());
   }
 
   /** Returns the truth-value of this Starlark value. */
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/actions/BuildInfoFileWriteActionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/actions/BuildInfoFileWriteActionTest.java
index 70e2b025f1933a..8724598d7f123f 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/actions/BuildInfoFileWriteActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/actions/BuildInfoFileWriteActionTest.java
@@ -78,6 +78,7 @@ private static Object exec(String... lines) throws Exception {
               BazelModuleContext.create(
                   Label.parseCanonicalUnchecked("//test:label"),
                   RepositoryMapping.ALWAYS_FALLBACK,
+                  /* mainRepoMapping= */ null,
                   "test/label.bzl",
                   /* loads= */ ImmutableList.of(),
                   /* bzlTransitiveDigest= */ new byte[0])),
diff --git a/src/test/java/com/google/devtools/build/lib/cmdline/LabelTest.java b/src/test/java/com/google/devtools/build/lib/cmdline/LabelTest.java
index 8a09a566f2de58..f099781f301681 100644
--- a/src/test/java/com/google/devtools/build/lib/cmdline/LabelTest.java
+++ b/src/test/java/com/google/devtools/build/lib/cmdline/LabelTest.java
@@ -419,6 +419,12 @@ public void testDisplayForm() throws Exception {
         .isEqualTo("@unremapped//:unremapped");
   }
 
+  @Test
+  public void testDisplayFormNullMapping() throws Exception {
+    assertThat(displayFormFor("//foo/bar:bar", null)).isEqualTo("//foo/bar:bar");
+    assertThat(displayFormFor("@@foo//bar:bar", null)).isEqualTo("@@foo//bar:bar");
+  }
+
   private static String shorthandDisplayFormFor(
       String rawLabel, RepositoryMapping repositoryMapping) throws Exception {
     return Label.parseCanonical(rawLabel).getShorthandDisplayForm(repositoryMapping);
diff --git a/src/test/java/com/google/devtools/build/lib/cmdline/PackageIdentifierTest.java b/src/test/java/com/google/devtools/build/lib/cmdline/PackageIdentifierTest.java
index 07f025f3f2c9bf..3336ed90524029 100644
--- a/src/test/java/com/google/devtools/build/lib/cmdline/PackageIdentifierTest.java
+++ b/src/test/java/com/google/devtools/build/lib/cmdline/PackageIdentifierTest.java
@@ -120,6 +120,7 @@ public void testDisplayFormInMainRepository() throws Exception {
                 RepositoryMapping.create(
                     ImmutableMap.of("foo", RepositoryName.create("bar")), RepositoryName.MAIN)))
         .isEqualTo("//some/pkg");
+    assertThat(pkg.getDisplayForm(null)).isEqualTo("//some/pkg");
   }
 
   @Test
@@ -139,5 +140,6 @@ public void testDisplayFormInExternalRepository() throws Exception {
                     ImmutableMap.of("local", RepositoryName.create("other_repo")),
                     RepositoryName.MAIN)))
         .isEqualTo("@@canonical//some/pkg");
+    assertThat(pkg.getDisplayForm(null)).isEqualTo("@@canonical//some/pkg");
   }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/cmdline/RepositoryNameTest.java b/src/test/java/com/google/devtools/build/lib/cmdline/RepositoryNameTest.java
index 482f2d2e779c52..71cb12ac7efb62 100644
--- a/src/test/java/com/google/devtools/build/lib/cmdline/RepositoryNameTest.java
+++ b/src/test/java/com/google/devtools/build/lib/cmdline/RepositoryNameTest.java
@@ -105,4 +105,21 @@ public void testGetDisplayForm() throws Exception {
                 .getDisplayForm(repositoryMapping))
         .isEqualTo("@@[unknown repo 'local' requested from @@owner]");
   }
+
+  @Test
+  public void testGetDisplayFormWithNullMapping() throws Exception {
+    assertThat(RepositoryName.create("").getDisplayForm(null)).isEmpty();
+    assertThat(RepositoryName.create("canonical").getDisplayForm(null)).isEqualTo("@@canonical");
+
+    assertThat(
+            RepositoryName.create("")
+                .toNonVisible(RepositoryName.create("owner"))
+                .getDisplayForm(null))
+        .isEqualTo("@@[unknown repo '' requested from @@owner]");
+    assertThat(
+            RepositoryName.create("canonical")
+                .toNonVisible(RepositoryName.create("owner"))
+                .getDisplayForm(null))
+        .isEqualTo("@@[unknown repo 'canonical' requested from @@owner]");
+  }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkIntegrationTest.java b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkIntegrationTest.java
index 331bc1e7d9c67c..7ddd7153602160 100644
--- a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkIntegrationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkIntegrationTest.java
@@ -1741,7 +1741,7 @@ def output_func(name):
 
     getConfiguredTarget("//test/starlark:cr");
     assertContainsEvent("output function cr");
-    assertContainsEvent("implementation @@//test/starlark:cr");
+    assertContainsEvent("implementation //test/starlark:cr");
   }
 
   @Test
diff --git a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleClassFunctionsTest.java b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleClassFunctionsTest.java
index 187cd6d0815293..32e068d24984b6 100644
--- a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleClassFunctionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleClassFunctionsTest.java
@@ -6088,6 +6088,7 @@ public void testLabelWithStrictVisibility() throws Exception {
             bzlLabel,
             RepositoryMapping.create(
                 ImmutableMap.of("my_module", currentRepo, "dep", otherRepo), currentRepo),
+            /* mainRepoMapping= */ null,
             "lib/label.bzl",
             /* loads= */ ImmutableList.of(),
             /* bzlTransitiveDigest= */ new byte[0]);
diff --git a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleImplementationFunctionsTest.java b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleImplementationFunctionsTest.java
index 56b63b339f9b82..3d796ca2018c78 100644
--- a/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleImplementationFunctionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleImplementationFunctionsTest.java
@@ -78,6 +78,7 @@
 import net.starlark.java.annot.Param;
 import net.starlark.java.annot.StarlarkMethod;
 import net.starlark.java.eval.EvalException;
+import net.starlark.java.eval.Mutability;
 import net.starlark.java.eval.Printer;
 import net.starlark.java.eval.Sequence;
 import net.starlark.java.eval.Starlark;
@@ -3710,7 +3711,13 @@ public void testPrintArgs() throws Exception {
     setRuleContext(createRuleContext("//foo:foo"));
     ev.exec("args = ruleContext.actions.args()", "args.add_all(['--foo', '--bar'])");
     Args args = (Args) ev.eval("args");
-    assertThat(new Printer().debugPrint(args, getStarlarkSemantics()).toString())
+    assertThat(
+            new Printer()
+                .debugPrint(
+                    args,
+                    StarlarkThread.createTransient(
+                        Mutability.create("test"), getStarlarkSemantics()))
+                .toString())
         .isEqualTo("--foo --bar");
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/starlark/util/BazelEvaluationTestCase.java b/src/test/java/com/google/devtools/build/lib/starlark/util/BazelEvaluationTestCase.java
index 721dc928a77284..03cfff25331a69 100644
--- a/src/test/java/com/google/devtools/build/lib/starlark/util/BazelEvaluationTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/starlark/util/BazelEvaluationTestCase.java
@@ -187,6 +187,7 @@ private Object newModule(ImmutableMap.Builder<String, Object> predeclared) {
     return BazelModuleContext.create(
         label,
         RepositoryMapping.ALWAYS_FALLBACK,
+        /* mainRepoMapping= */ null,
         "test/label.bzl",
         /* loads= */ ImmutableList.of(),
         /* bzlTransitiveDigest= */ new byte[0]);
diff --git a/src/test/java/net/starlark/java/eval/StarlarkEvaluationTest.java b/src/test/java/net/starlark/java/eval/StarlarkEvaluationTest.java
index e08bcd86bd4557..9b5ebf5980f951 100644
--- a/src/test/java/net/starlark/java/eval/StarlarkEvaluationTest.java
+++ b/src/test/java/net/starlark/java/eval/StarlarkEvaluationTest.java
@@ -377,7 +377,7 @@ public Structure proxyMethodsObject(StarlarkThread thread)
         useStarlarkThread = true)
     public String withArgsAndThread(
         StarlarkInt pos1, boolean pos2, boolean named, Sequence<?> args, StarlarkThread thread) {
-      String argsString = debugPrintArgs(args, thread.getSemantics());
+      String argsString = debugPrintArgs(args, thread);
       return "with_args_and_thread("
           + pos1
           + ", "
@@ -416,9 +416,11 @@ public String withKwargs(boolean pos, boolean named, Dict<String, Object> kwargs
           @Param(name = "foo", named = true, positional = true),
         },
         extraPositionals = @Param(name = "args"),
-        extraKeywords = @Param(name = "kwargs"))
-    public String withArgsAndKwargs(String foo, Tuple args, Dict<String, Object> kwargs) {
-      String argsString = debugPrintArgs(args, StarlarkSemantics.DEFAULT);
+        extraKeywords = @Param(name = "kwargs"),
+        useStarlarkThread = true)
+    public String withArgsAndKwargs(
+        String foo, Tuple args, Dict<String, Object> kwargs, StarlarkThread thread) {
+      String argsString = debugPrintArgs(args, thread);
       String kwargsString =
           "kwargs("
               + kwargs
@@ -436,12 +438,12 @@ public String toString() {
     }
   }
 
-  private static String debugPrintArgs(Iterable<?> args, StarlarkSemantics semantics) {
+  private static String debugPrintArgs(Iterable<?> args, StarlarkThread thread) {
     Printer p = new Printer();
     p.append("args(");
     String sep = "";
     for (Object arg : args) {
-      p.append(sep).debugPrint(arg, semantics);
+      p.append(sep).debugPrint(arg, thread);
       sep = ", ";
     }
     return p.append(")").toString();
diff --git a/src/test/py/bazel/bzlmod/bazel_module_test.py b/src/test/py/bazel/bzlmod/bazel_module_test.py
index 683869eeefac22..9834afb2c04457 100644
--- a/src/test/py/bazel/bzlmod/bazel_module_test.py
+++ b/src/test/py/bazel/bzlmod/bazel_module_test.py
@@ -942,6 +942,65 @@ def testInclude(self):
     )
     _, stdout, _ = self.RunBazel(['run', '//:main'])
     self.assertIn('main function => aaa@1.0', stdout)
+    
+
+  def testLabelDebugPrint(self):
+    """Tests that print emits labels in display form."""
+    self.ScratchFile(
+      'MODULE.bazel',
+      [
+        'bazel_dep(name="other_module", version="1.0")',
+        'local_path_override(module_name="other_module", path="other_module")',
+        'ext = use_extension("//:defs.bzl", "my_ext")',
+        'use_repo(ext, "repo")',
+      ]
+    )
+
+    self.ScratchFile(
+      'WORKSPACE.bzlmod',
+      [
+        'load("//:defs.bzl", "my_repo")',
+        'my_repo(name = "workspace_repo", type = "workspace")',
+      ]
+    )
+
+    self.ScratchFile('other_module/MODULE.bazel', ['module(name="other_module", version="1.0")'])
+
+    self.ScratchFile(
+      'defs.bzl',
+      [
+        'print("toplevel", Label("//:foo"), Label("@other_module//:bar"), Label("@@canonical_name//:baz"))',
+        'def _repo_impl(ctx):',
+        '  print("repo:" + ctx.attr.type, Label("//:foo"), Label("@other_module//:bar"), Label("@@canonical_name//:baz"))',
+        '  ctx.file("BUILD")',
+        '  ctx.file("data.bzl", "repo_data = \\"repo\\"")',
+        'my_repo = repository_rule(implementation=_repo_impl, attrs={"type":attr.string()})',
+        'def _ext_impl(ctx):',
+        '  print("ext", Label("//:foo"), Label("@other_module//:bar"), Label("@@canonical_name//:baz"))',
+        '  my_repo(name = "repo", type = "module")',
+        'my_ext = module_extension(implementation=_ext_impl)',
+        'def _rule_impl(ctx):',
+        '  print("rule", Label("//:foo"), Label("@other_module//:bar"), Label("@@canonical_name//:baz"))',
+        'my_rule = rule(implementation=_rule_impl)',
+      ]
+    )
+    self.ScratchFile(
+      "BUILD",
+      [
+        'load("@repo//:data.bzl", "repo_data")',
+        'load("@workspace_repo//:data.bzl", "repo_data")',
+        'load(":defs.bzl", "my_rule")',
+        'my_rule(name = "my_rule")',
+      ]
+    )
+
+    _, _, stderr = self.RunBazel(['build', '--enable_workspace', '//:my_rule'])
+    stderr = '\n'.join(stderr)
+    self.assertIn('toplevel //:foo @other_module//:bar @@canonical_name//:baz', stderr)
+    self.assertIn('repo:module //:foo @other_module//:bar @@canonical_name//:baz', stderr)
+    self.assertIn('repo:workspace //:foo @other_module//:bar @@canonical_name//:baz', stderr)
+    self.assertIn('ext //:foo @other_module//:bar @@canonical_name//:baz', stderr)
+    self.assertIn('rule //:foo @other_module//:bar @@canonical_name//:baz', stderr)
 
 
 if __name__ == '__main__':
diff --git a/src/test/shell/bazel/platforms_test.sh b/src/test/shell/bazel/platforms_test.sh
index c42d78d877c5a5..053e123684d38d 100755
--- a/src/test/shell/bazel/platforms_test.sh
+++ b/src/test/shell/bazel/platforms_test.sh
@@ -115,7 +115,7 @@ platform(
 EOF
 
   bazel build --experimental_platforms_api=true :a &> $TEST_log || fail "Build failed"
-  expect_log 'The label is: @@//:my_platform'
+  expect_log 'The label is: //:my_platform'
 }
 
 run_suite "platform repo test"