Raise an early error on invalid labels in transitions inputs/outputs

When a label pointing to an unavailable repository is specified as a transition's input or output, an early error is raised instead of crashing during transition evaluation.

Fixes bazelbuild#19632

Closes bazelbuild#19634.

PiperOrigin-RevId: 570634319
Change-Id: Icda2946313898db2372484b4f845aafcf5a8b272

src/main/java/com/google/devtools/build/lib/rules/config/ConfigGlobalLibrary.java

@@ -21,6 +21,7 @@
 import com.google.devtools.build.lib.analysis.config.StarlarkDefinedConfigTransition.Settings;
 import com.google.devtools.build.lib.cmdline.BazelModuleContext;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
 import com.google.devtools.build.lib.starlarkbuildapi.config.ConfigGlobalLibraryApi;
 import com.google.devtools.build.lib.starlarkbuildapi.config.ConfigurationTransitionApi;
 import java.util.HashSet;
@@ -57,9 +58,11 @@ public ConfigurationTransitionApi transition(
     // that info through StarlarkSemantics) or add an "exec = True" paramter to Starlark's
     // transition() function.
     boolean isExecTransition = implementation.getLocation().file().endsWith("_exec_platforms.bzl");
-    validateBuildSettingKeys(inputsList, Settings.INPUTS, isExecTransition);
-    validateBuildSettingKeys(outputsList, Settings.OUTPUTS, isExecTransition);
     BazelModuleContext moduleContext = BazelModuleContext.ofInnermostBzlOrThrow(thread);
+    validateBuildSettingKeys(
+        inputsList, Settings.INPUTS, isExecTransition, moduleContext.packageContext());
+    validateBuildSettingKeys(
+        outputsList, Settings.OUTPUTS, isExecTransition, moduleContext.packageContext());
     Location location = thread.getCallerLocation();
     return StarlarkDefinedConfigTransition.newRegularTransition(
         implementation,
@@ -79,16 +82,22 @@ public ConfigurationTransitionApi analysisTestTransition(
       throws EvalException {
     Map<String, Object> changedSettingsMap =
         Dict.cast(changedSettings, String.class, Object.class, "changed_settings dict");
-    validateBuildSettingKeys(
-        changedSettingsMap.keySet(), Settings.OUTPUTS, /* isExecTransition= */ false);
     BazelModuleContext moduleContext = BazelModuleContext.ofInnermostBzlOrThrow(thread);
+    validateBuildSettingKeys(
+        changedSettingsMap.keySet(),
+        Settings.OUTPUTS,
+        /* isExecTransition= */ false,
+        moduleContext.packageContext());
     Location location = thread.getCallerLocation();
     return StarlarkDefinedConfigTransition.newAnalysisTestTransition(
         changedSettingsMap, moduleContext.repoMapping(), moduleContext.label(), location);
   }
 
   private void validateBuildSettingKeys(
-      Iterable<String> optionKeys, Settings keyErrorDescriptor, boolean isExecTransition)
+      Iterable<String> optionKeys,
+      Settings keyErrorDescriptor,
+      boolean isExecTransition,
+      Label.PackageContext packageContext)
       throws EvalException {
 
     HashSet<String> processedOptions = Sets.newHashSet();
@@ -97,8 +106,16 @@ private void validateBuildSettingKeys(
     for (String optionKey : optionKeys) {
       if (!optionKey.startsWith(COMMAND_LINE_OPTION_PREFIX)) {
         try {
-          var unused = Label.parseCanonicalUnchecked(optionKey);
-        } catch (IllegalArgumentException e) {
+          Label label = Label.parseWithRepoContext(optionKey, packageContext);
+          if (!label.getRepository().isVisible()) {
+            throw Starlark.errorf(
+                "invalid transition %s '%s': no repo visible as @%s from %s",
+                singularErrorDescriptor,
+                label,
+                label.getRepository().getName(),
+                label.getRepository().getOwnerRepoDisplayString());
+          }
+        } catch (LabelSyntaxException e) {
           throw Starlark.errorf(
               "invalid transition %s '%s'. If this is intended as a native option, "
                   + "it must begin with //command_line_option: %s",

src/test/java/com/google/devtools/build/lib/rules/LabelBuildSettingTest.java

@@ -339,4 +339,48 @@ public void transitionOutput_otherRepo() throws Exception {
     assertThat(getConfiguredTarget("//test:buildme")).isNotNull();
     assertNoEvents();
   }
+
+  @Test
+  public void testInvisibleRepoInLabelResultsInEarlyError() throws Exception {
+    setBuildLanguageOptions("--enable_bzlmod");
+
+    scratch.file("MODULE.bazel");
+    scratch.file(
+        "test/defs.bzl",
+        "def _setting_impl(ctx):",
+        "  return []",
+        "string_flag = rule(",
+        "  implementation = _setting_impl,",
+        "  build_setting = config.string(flag=True),",
+        ")",
+        "def _transition_impl(settings, attr):",
+        "  return {'//test:formation': 'mesa'}",
+        "formation_transition = transition(",
+        "  implementation = _transition_impl,",
+        "  inputs = ['@foobar//test:formation'],", // invalid repo name
+        "  outputs = ['//test:formation'],",
+        ")",
+        "def _impl(ctx):",
+        "  return []",
+        "state = rule(",
+        "  implementation = _impl,",
+        "  cfg = formation_transition,",
+        "  attrs = {",
+        "    '_allowlist_function_transition': attr.label(",
+        "        default = '//tools/allowlists/function_transition_allowlist',",
+        "    ),",
+        "  })");
+    scratch.file(
+        "test/BUILD",
+        "load('//test:defs.bzl', 'state', 'string_flag')",
+        "state(name = 'arizona')",
+        "string_flag(name = 'formation', build_setting_default = 'canyon')");
+
+    reporter.removeHandler(failFastHandler);
+    getConfiguredTarget("//test:arizona");
+
+    assertContainsEvent(
+        "Error in transition: invalid transition input '@[unknown repo 'foobar' requested from @]"
+            + "//test:formation': no repo visible as @foobar from main repository");
+  }
 }