Handle access to files under invalid repo names gracefully

Fixes #24621

Closes #24666.

PiperOrigin-RevId: 708009380
Change-Id: I8706f1fdfba2282a27e84dff610e6511c1060e23

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

@@ -38,6 +38,7 @@
 import com.google.devtools.build.lib.bazel.repository.downloader.HttpUtils;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.LabelConstants;
+import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.ExtendedEventHandler.FetchProgress;
@@ -1554,11 +1555,16 @@ protected RepoCacheFriendlyPath toRepoCacheFriendlyPath(Path path, ShouldWatch s
       PathFragment relPath = path.relativeTo(outputBaseExternal);
       if (!relPath.isEmpty()) {
         // The file is under a repo root.
-        String repoName = relPath.getSegment(0);
+        RepositoryName repoName;
+        try {
+          repoName = RepositoryName.create(relPath.getSegment(0));
+        } catch (LabelSyntaxException e) {
+          throw Starlark.errorf(
+              "attempted to watch path under external repository directory: %s", e.getMessage());
+        }
         PathFragment repoRelPath =
-            relPath.relativeTo(PathFragment.createAlreadyNormalized(repoName));
-        return RepoCacheFriendlyPath.createInsideWorkspace(
-            RepositoryName.createUnvalidated(repoName), repoRelPath);
+            relPath.relativeTo(PathFragment.createAlreadyNormalized(repoName.getName()));
+        return RepoCacheFriendlyPath.createInsideWorkspace(repoName, repoRelPath);
       }
     }
     // The file is just under a random absolute path.

src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java

@@ -24,6 +24,7 @@
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.LabelConstants;
+import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
@@ -404,8 +405,15 @@ public static void addExternalFilesDependencies(
       // repository path.
       return;
     }
-    String repositoryName = repositoryPath.getSegment(0);
-    env.getValue(RepositoryDirectoryValue.key(RepositoryName.createUnvalidated(repositoryName)));
+    RepositoryName repositoryName;
+    try {
+      repositoryName = RepositoryName.create(repositoryPath.getSegment(0));
+    } catch (LabelSyntaxException ignored) {
+      // The directory of a repository with an invalid name can never exist, so we don't need to
+      // add a dependency on it.
+      return;
+    }
+    env.getValue(RepositoryDirectoryValue.key(repositoryName));
   }
 
   /** Sets up a mapping of environment variables to use. */

src/test/shell/bazel/starlark_repository_test.sh

@@ -3573,4 +3573,22 @@ EOF
     @repo//... &> $TEST_log || fail "expected Bazel to succeed"
 }
 
+function test_dependency_on_repo_with_invalid_name() {
+  cat >> $(setup_module_dot_bazel) <<'EOF'
+my_repo = use_repo_rule("//:repo.bzl", "my_repo")
+my_repo(name="repo")
+EOF
+  touch BUILD
+  cat > repo.bzl <<'EOF'
+def _impl(ctx):
+  ctx.read("../@invalid_name@/file")
+
+my_repo = repository_rule(_impl)
+EOF
+
+  bazel build @repo//... &> $TEST_log && fail "expected Bazel to fail"
+  expect_not_log "Unrecoverable error"
+  expect_log "attempted to watch path under external repository directory: invalid repository name '@invalid_name@'"
+}
+
 run_suite "local repository tests"