feat: freeze typed metrics registry and bounded exemplars

tests/unit/test_check_metrics_boundaries.py

@@ -0,0 +1,76 @@
+import subprocess
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+CHECKER = ROOT / "scripts" / "check-metrics-boundaries.py"
+
+
+class MetricsBoundaryTests(unittest.TestCase):
+    def run_checker(self, root: Path, *paths: str) -> subprocess.CompletedProcess[str]:
+        return subprocess.run(
+            ["python3", str(CHECKER), "--root", str(root), "--files", *paths],
+            text=True,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            check=False,
+        )
+
+    def test_rejects_direct_alias_import_reexport_and_wrapper_bypasses(self) -> None:
+        cases = {
+            "direct.rs": 'metrics::counter!("bad").increment(1);',
+            "alias.rs": 'use metrics as m; m::counter!("bad").increment(1);',
+            "import.rs": 'use metrics::counter; counter!("bad").increment(1);',
+            "reexport.rs": 'pub use metrics::histogram;',
+            "absolute.rs": '::metrics::gauge!("bad").set(1.0);',
+            "wrapper.rs": 'macro_rules! bad { () => { metrics::counter!("bad") } }',
+        }
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            paths = []
+            for name, content in cases.items():
+                path = root / "apps" / "demo" / "src" / name
+                path.parent.mkdir(parents=True, exist_ok=True)
+                path.write_text(content, encoding="utf-8")
+                paths.append(str(path.relative_to(root)))
+            result = self.run_checker(root, *paths)
+            self.assertNotEqual(result.returncode, 0)
+            for name in cases:
+                self.assertIn(name, result.stderr)
+            self.assertNotIn(str(root), result.stderr)
+
+    def test_allows_typed_facade_and_narrow_observability_adapter(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            product = root / "apps" / "demo" / "src" / "main.rs"
+            adapter = root / "crates" / "crank-observability" / "src" / "instrumentation.rs"
+            product.parent.mkdir(parents=True)
+            adapter.parent.mkdir(parents=True)
+            product.write_text("crank_metrics::record_cache_outcome(value);", encoding="utf-8")
+            adapter.write_text("metrics::describe_counter!(definition.name, definition.description);", encoding="utf-8")
+            result = self.run_checker(root, str(product.relative_to(root)), str(adapter.relative_to(root)))
+            self.assertEqual(result.returncode, 0, result.stderr)
+
+    def test_explicit_missing_traversal_and_symlink_fail_closed(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            outside = root.parent / "metrics-boundary-outside.rs"
+            outside.write_text('metrics::counter!("bad");', encoding="utf-8")
+            try:
+                for path in ["missing.rs", "../metrics-boundary-outside.rs"]:
+                    result = self.run_checker(root, path)
+                    self.assertNotEqual(result.returncode, 0)
+                target = root / "target.rs"
+                target.write_text("", encoding="utf-8")
+                link = root / "link.rs"
+                link.symlink_to(target)
+                result = self.run_checker(root, "link.rs")
+                self.assertNotEqual(result.returncode, 0)
+            finally:
+                outside.unlink(missing_ok=True)
+
+
+if __name__ == "__main__":
+    unittest.main()