fix: narrow lockfile plugin CI selection

tests/test_plugin_catalog.py

@@ -1799,6 +1799,41 @@ def test_ci_selection_treats_cargo_lock_change_as_all_plugins(self) -> None:
                 },
             )
 
+    def test_ci_selection_keeps_cargo_lock_with_plugin_change_plugin_scoped(self) -> None:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = Path(tmpdir)
+            git = lambda *args: subprocess.run(  # noqa: E731
+                ["git", *args],
+                cwd=root,
+                text=True,
+                capture_output=True,
+                check=True,
+            )
+            git("init")
+            git("config", "user.name", "Test User")
+            git("config", "user.email", "test@example.com")
+            (root / "Cargo.toml").write_text(
+                '[workspace]\nmembers = ["plugins/rust/python-package/rate_limiter", "plugins/rust/python-package/pii_filter"]\n'
+            )
+            rate_limiter = self._create_plugin(root, "rate_limiter")
+            self._create_plugin(root, "pii_filter")
+            (root / "Cargo.lock").write_text("# seed\n")
+            git("add", ".")
+            git("commit", "--no-verify", "-m", "seed layout")
+            base_sha = git("rev-parse", "HEAD").stdout.strip()
+
+            (rate_limiter / "README.md").write_text("# rate_limiter\n\nUpdated docs.\n")
+            (root / "Cargo.lock").write_text("# updated\n")
+            git("add", ".")
+            git("commit", "--no-verify", "-m", "plugin lockfile update")
+
+            result = run_catalog("ci-selection", str(root), "diff", base_sha, "HEAD")
+            self.assertEqual(result.returncode, 0, result.stderr)
+            payload = json.loads(result.stdout)
+            self.assertEqual(payload["plugins"], ["rate_limiter"])
+            self.assertEqual(payload["cargo_packages"], ["rate_limiter"])
+            self.assertEqual(payload["plugin_count"], 1)
+
     def test_ci_selection_treats_deny_config_change_as_all_plugins(self) -> None:
         with tempfile.TemporaryDirectory() as tmpdir:
             root = Path(tmpdir)

tools/plugin_catalog.py

@@ -23,7 +23,6 @@
     ".config/",
     ".github/workflows/",
     "Cargo.toml",
-    "Cargo.lock",
     "deny.toml",
     "crates/",
     "README.md",
@@ -531,7 +530,10 @@ def _changed_plugins_for_records(
     changed: set[str] = set()
     managed_prefix = f"{MANAGED_ROOT.as_posix()}/"
     integration_prefix = "plugins/tests/"
+    has_lockfile_change = "Cargo.lock" in changed_paths
     for path in changed_paths:
+        if path == "Cargo.lock":
+            continue
         if not path.startswith(managed_prefix):
             if not path.startswith(integration_prefix):
                 continue
@@ -544,6 +546,8 @@ def _changed_plugins_for_records(
         slug = relative.split("/", maxsplit=1)[0]
         if slug in plugin_lookup:
             changed.add(slug)
+    if has_lockfile_change and not changed:
+        return sorted(plugin_lookup)
     return sorted(changed)