fix: Defer tomlkit import until uv management is confirmed

Author: erral

src/mxdev/uv.py

@@ -24,23 +24,30 @@ def read(self, state: State) -> None:
         pass
 
     def write(self, state: State) -> None:
-        try:
-            import tomlkit
-        except ImportError:
-            raise RuntimeError("tomlkit is required for the uv hook. Install it with: pip install mxdev[uv]")
-
         pyproject_path = Path(state.configuration.settings.get("directory", ".")) / "pyproject.toml"
         if not pyproject_path.exists():
             logger.debug("[%s] pyproject.toml not found, skipping.", self.namespace)
             return
 
         try:
-            with pyproject_path.open("r", encoding="utf-8") as f:
-                doc = tomlkit.load(f)
+            content = pyproject_path.read_text(encoding="utf-8")
         except OSError as e:
             logger.error("[%s] Failed to read pyproject.toml: %s", self.namespace, e)
             return
 
+        if "[tool.uv]" not in content:
+            logger.debug(
+                "[%s] Project not explicitly managed by uv ([tool.uv] managed=true missing), skipping.", self.namespace
+            )
+            return
+
+        try:
+            import tomlkit
+        except ImportError:
+            raise RuntimeError("tomlkit is required for the uv hook. Install it with: pip install mxdev[uv]")
+
+        doc = tomlkit.loads(content)
+
         # Check for the UV managed signal
         tool_uv = doc.get("tool", {}).get("uv", {})
         if tool_uv.get("managed") is not True:

tests/test_uv.py

@@ -310,6 +310,32 @@ def fake_import(name, *args, **kw):
     assert "tomlkit is required for the uv hook" in str(excinfo.value)
 
 
+def test_hook_does_not_require_tomlkit_if_not_uv_managed(mocker, tmp_path, monkeypatch):
+    monkeypatch.chdir(tmp_path)
+    hook = UvPyprojectUpdater()
+
+    (tmp_path / "mx.ini").write_text("[settings]")
+    config = Configuration("mx.ini")
+    state = State(config)
+
+    (tmp_path / "pyproject.toml").write_text("[project]\\nname = 'test'\\n")
+
+    mocker.patch.dict(sys.modules, {"tomlkit": None})
+    import builtins
+
+    orig_import = builtins.__import__
+
+    def fake_import(name, *args, **kw):
+        if name == "tomlkit":
+            raise ImportError("No module named 'tomlkit'")
+        return orig_import(name, *args, **kw)
+
+    mocker.patch("builtins.__import__", side_effect=fake_import)
+
+    # Should not raise any error, even though tomlkit import is mocked to fail
+    hook.write(state)
+
+
 def test_hook_resolves_path_relative_to_config(mocker, tmp_path, monkeypatch):
     monkeypatch.chdir(tmp_path)