[7.1.0] Improve use_repo_rule error when not referencing a repository_rule

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

@@ -620,7 +620,7 @@ public RunModuleExtensionResult run(
       // Instiantiate the repos one by one.
       for (InnateExtensionRepo repo : repos) {
         Object exported = repo.loadedBzl().getModule().getGlobal(repo.ruleName());
-        if (!(exported instanceof RepositoryRuleFunction)) {
+        if (exported == null) {
           ImmutableSet<String> exportedRepoRules =
               repo.loadedBzl().getModule().getGlobals().entrySet().stream()
                   .filter(e -> e.getValue() instanceof RepositoryRuleFunction)
@@ -636,6 +636,17 @@ public RunModuleExtensionResult run(
                   repo.tag().getLocation(),
                   SpellChecker.didYouMean(repo.ruleName(), exportedRepoRules)),
               Transience.PERSISTENT);
+        } else if (!(exported instanceof RepositoryRuleFunction)) {
+          throw new SingleExtensionEvalFunctionException(
+              ExternalDepsException.withMessage(
+                  Code.BAD_MODULE,
+                  "%s exports a value called %s of type %s, yet a repository_rule is requested"
+                      + " at %s",
+                  repo.bzlLabel(),
+                  repo.ruleName(),
+                  Starlark.type(exported),
+                  repo.tag().getLocation()),
+              Transience.PERSISTENT);
         }
         RepositoryRuleFunction repoRule = (RepositoryRuleFunction) exported;
         Dict<String, Object> kwargs = repo.tag().getAttributeValues().attributes();

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

@@ -2448,7 +2448,35 @@ public void innate_noSuchRepoRule() throws Exception {
         "load('@data//:data.bzl', self_data='data')",
         "data=self_data");
     scratch.file(
-        workspaceRoot.getRelative("repo.bzl").getPathString(), "data_repo = 3  # not a repo rule");
+        workspaceRoot.getRelative("repo.bzl").getPathString(),
+        "# not a repo rule",
+        "def data_repo(name):",
+        "    pass");
+
+    SkyKey skyKey = BzlLoadValue.keyForBuild(Label.parseCanonical("//:data.bzl"));
+    reporter.removeHandler(failFastHandler);
+    EvaluationResult<BzlLoadValue> result =
+        evaluator.evaluate(ImmutableList.of(skyKey), evaluationContext);
+    assertThat(result.hasError()).isTrue();
+    assertThat(result.getError().getException())
+        .hasMessageThat()
+        .contains(
+            "//:repo.bzl exports a value called data_repo of type function, yet a repository_rule"
+                + " is requested at /ws/MODULE.bazel");
+  }
+
+  @Test
+  public void innate_noSuchValue() throws Exception {
+    scratch.file(
+        workspaceRoot.getRelative("MODULE.bazel").getPathString(),
+        "data_repo = use_repo_rule('//:repo.bzl', 'data_repo')",
+        "data_repo(name='data', data='get up at 6am.')");
+    scratch.file(workspaceRoot.getRelative("BUILD").getPathString());
+    scratch.file(
+        workspaceRoot.getRelative("data.bzl").getPathString(),
+        "load('@data//:data.bzl', self_data='data')",
+        "data=self_data");
+    scratch.file(workspaceRoot.getRelative("repo.bzl").getPathString(), "");
 
     SkyKey skyKey = BzlLoadValue.keyForBuild(Label.parseCanonical("//:data.bzl"));
     reporter.removeHandler(failFastHandler);