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

Previously we enforced that the canonical repo name had to correspond to a module (i.e. not an extension-generated repo). This makes no sense, so this change simple deletes that enforcement.

To compensate for the lack of checks whether the repo exists at all, we add an additional check after requesting the BzlmodRepoRuleValues that all requested repos must exist.

Fixes bazelbuild#21621

PiperOrigin-RevId: 615733963
Change-Id: Icf706b36f0e8d3c775bc26528948e5102910d4a0

Author: Wyverald

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(
         [