New mapping

site/en/external/extension.md

@@ -165,6 +165,14 @@ several repo visibility rules:
         the apparent name `foo`, and the extension generates a repo with the
         specified name `foo`, then for all repos generated by that extension
         `foo` refers to the former.
+*   Similarly, in a module extension's implementation function, repos created
+    by the extension can refer to each other by their apparent names in
+    attributes, regardless of the order in which they are created.
+    *   In case of a conflict with a repository visible to the module, labels
+        passed to repository rule attributes can be wrapped in a call to
+        [`Label`](/rules/lib/toplevel/attr#label) to ensure that they refer to
+        the repo visible to the module instead of the repo generated by the
+        extension of the same name.
 
 ## Best practices
 

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionEvalStarlarkThreadContext.java

@@ -67,27 +67,31 @@ record RepoRuleCall(
 
   private final String repoPrefix;
   private final PackageIdentifier basePackageId;
-  private final RepositoryMapping repoMapping;
+  private final RepositoryMapping baseRepoMapping;
   private final BlazeDirectories directories;
   private final ExtendedEventHandler eventHandler;
   private final Map<String, RepoRuleCall> deferredRepos = new LinkedHashMap<>();
 
   public ModuleExtensionEvalStarlarkThreadContext(
       String repoPrefix,
       PackageIdentifier basePackageId,
-      RepositoryMapping repoMapping,
+      RepositoryMapping baseRepoMapping,
       RepositoryMapping mainRepoMapping,
       BlazeDirectories directories,
       ExtendedEventHandler eventHandler) {
     super(() -> mainRepoMapping);
     this.repoPrefix = repoPrefix;
     this.basePackageId = basePackageId;
-    this.repoMapping = repoMapping;
+    this.baseRepoMapping = baseRepoMapping;
     this.directories = directories;
     this.eventHandler = eventHandler;
   }
 
-  public void lazilyCreateRepos(
+  /**
+   * Records a call to a repo rule that should be created at the end of the module extension
+   * evaluation.
+   */
+  public void lazilyCreateRepo(
       StarlarkThread thread, Dict<String, Object> kwargs, RuleClass ruleClass)
       throws EvalException {
     Object nameValue = kwargs.getOrDefault("name", Starlark.NONE);
@@ -106,18 +110,34 @@ public void lazilyCreateRepos(
         name,
         new RepoRuleCall(
             ruleClass,
+            // The extension may mutate the values of the kwargs after this function returns.
             (Dict<String, Object>) deepCloneStarlarkObject(kwargs),
             thread.getCallerLocation(),
             thread.getCallStack()));
   }
 
   /**
-   * Returns the repos generated by the extension so far. The key is the "internal name" (as
-   * specified by the extension) of the repo, and the value is the package containing (only) the
-   * repo rule.
+   * Evaluates the repo rule calls recorded by {@link #lazilyCreateRepo} and returns all repos
+   * generated by the extension. The key is the "internal name" (as specified by the extension) of
+   * the repo, and the value is the package containing (only) the repo rule.
    */
   public ImmutableMap<String, RepoSpec> createAndGetRepos(StarlarkSemantics starlarkSemantics)
       throws EvalException, InterruptedException {
+    // LINT.IfChange
+    // Make it possible to refer to extension repos in the label attributes of another extension
+    // repo. Wrapping a label in Label(...) ensures that it is evaluated with respect to the
+    // containing module's repo mapping instead.
+    ImmutableMap.Builder<String, RepositoryName> fullRepoMappingEntries = ImmutableMap.builder();
+    fullRepoMappingEntries.putAll(baseRepoMapping.entries());
+    fullRepoMappingEntries.putAll(
+        Maps.asMap(
+            deferredRepos.keySet(),
+            apparentName -> RepositoryName.createUnvalidated(repoPrefix + apparentName)));
+    RepositoryMapping fullRepoMapping =
+        RepositoryMapping.create(
+            fullRepoMappingEntries.buildKeepingLast(), baseRepoMapping.ownerRepo());
+    // LINT.ThenChange(//src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionRepoMappingEntriesFunction.java)
+
     ImmutableMap.Builder<String, RepoSpec> repoSpecs = ImmutableMap.builder();
     for (var entry : deferredRepos.entrySet()) {
       String name = entry.getKey();
@@ -127,7 +147,7 @@ public ImmutableMap<String, RepoSpec> createAndGetRepos(StarlarkSemantics starla
         Rule rule =
             BzlmodRepoRuleCreator.createRule(
                 basePackageId,
-                repoMapping,
+                fullRepoMapping,
                 directories,
                 starlarkSemantics,
                 eventHandler,
@@ -162,6 +182,7 @@ public ImmutableMap<String, RepoSpec> createAndGetRepos(StarlarkSemantics starla
     return repoSpecs.buildOrThrow();
   }
 
+  /** Deep-clones a potentially mutable Starlark object. Immutable (sub-)objects are not cloned. */
   private static Object deepCloneStarlarkObject(Object x) {
     if (x instanceof String || x instanceof Boolean) {
       return x;

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionRepoMappingEntriesFunction.java

@@ -70,9 +70,11 @@ private ModuleExtensionRepoMappingEntriesValue computeRepoMappingEntries(
     // extension generates an internal repo name "bar", then within a repo generated by the
     // extension, "bar" will refer to the latter. We should explore a way to differentiate between
     // the two to avoid any surprises.
+    // LINT.IfChange
     ImmutableMap.Builder<String, RepositoryName> entries = ImmutableMap.builder();
     entries.putAll(bazelDepGraphValue.getFullRepoMapping(moduleKey).entries());
     entries.putAll(extensionEvalValue.getCanonicalRepoNameToInternalNames().inverse());
     return ModuleExtensionRepoMappingEntriesValue.create(entries.buildKeepingLast(), moduleKey);
+    // LINT.ThenChange(//src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionEvalStarlarkThreadContext.java)
   }
 }

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/SingleExtensionEvalFunction.java

@@ -569,7 +569,7 @@ RunModuleExtensionResult run(
         SingleExtensionUsagesValue usagesValue,
         StarlarkSemantics starlarkSemantics,
         ModuleExtensionId extensionId,
-        RepositoryMapping repositoryMapping)
+        RepositoryMapping mainRepositoryMapping)
         throws InterruptedException, SingleExtensionEvalFunctionException;
   }
 

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

@@ -222,7 +222,7 @@ public Object call(StarlarkThread thread, Tuple args, Dict<String, Object> kwarg
       if (!isExported()) {
         throw new EvalException("attempting to instantiate a non-exported repository rule");
       }
-      extensionEvalContext.lazilyCreateRepos(thread, kwargs, getRuleClass());
+      extensionEvalContext.lazilyCreateRepo(thread, kwargs, getRuleClass());
       return Starlark.NONE;
     }
 

src/main/java/net/starlark/java/eval/EvalException.java

@@ -57,6 +57,10 @@ public EvalException(Throwable cause) {
     super(getCauseMessage(cause), cause);
   }
 
+  /**
+   * Constructs an EvalException using the same message as the cause exception and with the given
+   * callstack.
+   */
   public EvalException(Throwable cause, List<StarlarkThread.CallStackEntry> callstack) {
     this(cause);
     this.callstack = ImmutableList.copyOf(callstack);

src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionResolutionTest.java

@@ -3066,17 +3066,17 @@ def _other_ext_impl(ctx):
     }
     assertThat((List<?>) result.get(skyKey).getModule().getGlobal("foo_list"))
         .containsExactly(
-            "@@+other_ext+other_foo//:target1",
-            "@@+other_ext+other_bar//:target2",
+            "@@+ext+foo//:target1",
+            "@@+ext+bar//:target2",
             "@@+other_ext+other_foo//:target3",
             "@@+other_ext+other_bar//:target4",
             "@@+other_ext+other_foo//:foo",
             "@@+other_ext+other_bar//:bar")
         .inOrder();
     assertThat((List<?>) result.get(skyKey).getModule().getGlobal("bar_list"))
         .containsExactly(
-            "@@+other_ext+other_foo//:target5",
-            "@@+other_ext+other_bar//:target6",
+            "@@+ext+foo//:target5",
+            "@@+ext+bar//:target6",
             "@@+other_ext+other_foo//:target7",
             "@@+other_ext+other_bar//:target8",
             "@@+other_ext+other_foo//:foo",