[7.1.1] Allow any canonical repo name to be used with bazel mod show_repo

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

@@ -334,18 +334,7 @@ public ImmutableMap<String, RepositoryName> resolveToRepoNames(
         ImmutableMap<String, ImmutableSet<ModuleKey>> modulesIndex,
         ImmutableMap<ModuleKey, AugmentedModule> depGraph,
         ImmutableMap<ModuleKey, RepositoryName> moduleKeyToCanonicalNames,
-        RepositoryMapping mapping)
-        throws InvalidArgumentException {
-      if (depGraph.values().stream()
-          .filter(m -> moduleKeyToCanonicalNames.get(m.getKey()).equals(repoName()) && m.isUsed())
-          .findAny()
-          .isEmpty()) {
-        throw new InvalidArgumentException(
-            String.format(
-                "No module with the canonical repo name @@%s exists in the dependency graph",
-                repoName().getName()),
-            Code.INVALID_ARGUMENTS);
-      }
+        RepositoryMapping mapping) {
       return ImmutableMap.of(toString(), repoName());
     }
 

src/main/java/com/google/devtools/build/lib/bazel/commands/ModCommand.java

@@ -94,6 +94,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Optional;
@@ -494,6 +495,14 @@ private BlazeCommandResult execInternal(CommandEnvironment env, OptionsParsingRe
                         e ->
                             (BzlmodRepoRuleValue)
                                 result.get(BzlmodRepoRuleValue.key(e.getValue()))));
+        for (Map.Entry<String, BzlmodRepoRuleValue> entry : targetRepoRuleValues.entrySet()) {
+          if (entry.getValue() == BzlmodRepoRuleValue.REPO_RULE_NOT_FOUND_VALUE) {
+            return reportAndCreateFailureResult(
+                env,
+                String.format("In repo argument %s: no such repo", entry.getKey()),
+                Code.INVALID_ARGUMENTS);
+          }
+        }
       }
     } catch (InterruptedException e) {
       String errorMessage = "mod command interrupted: " + e.getMessage();

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

@@ -303,10 +303,10 @@ public void resolve_canonicalRepoName_notFound() throws Exception {
                 baseModuleUnusedDeps,
                 /* includeUnused= */ true,
                 /* warnUnused= */ true));
-    assertThrows(
-        InvalidArgumentException.class,
-        () ->
-            arg.resolveToRepoNames(modulesIndex, depGraph, moduleKeyToCanonicalNames, rootMapping));
+    // The repo need not exist in the "repo -> repo" case.
+    assertThat(
+            arg.resolveToRepoNames(modulesIndex, depGraph, moduleKeyToCanonicalNames, rootMapping))
+        .containsExactly("@@bar~1.0", RepositoryName.create("bar~1.0"));
   }
 
   @Test
@@ -341,9 +341,8 @@ public void resolve_canonicalRepoName_unused() throws Exception {
         .containsExactly(foo1);
 
     // resolving to repo names doesn't care about unused deps.
-    assertThrows(
-        InvalidArgumentException.class,
-        () ->
-            arg.resolveToRepoNames(modulesIndex, depGraph, moduleKeyToCanonicalNames, rootMapping));
+    assertThat(
+            arg.resolveToRepoNames(modulesIndex, depGraph, moduleKeyToCanonicalNames, rootMapping))
+        .containsExactly("@@foo~1.0", RepositoryName.create("foo~1.0"));
   }
 }

src/test/py/bazel/bzlmod/mod_command_test.py

@@ -465,6 +465,18 @@ def testShowRepoThrowsUnusedModule(self):
         stderr,
     )
 
+  def testShowRepoThrowsNonexistentRepo(self):
+    _, _, stderr = self.RunBazel(
+        ['mod', 'show_repo', '@@lol'],
+        allow_failure=True,
+        rstrip=True,
+    )
+    self.assertIn(
+        "ERROR: In repo argument @@lol: no such repo. Type 'bazel help mod' "
+        'for syntax and help.',
+        stderr,
+    )
+
   def testDumpRepoMapping(self):
     _, stdout, _ = self.RunBazel(
         [