fix: revert watchfiles to optional-dependency (#118)

Author: manzt

.changeset/itchy-dolphins-kick.md

@@ -1,5 +1,5 @@
 ---
-"anywidget": patch
+"anywidget": minor
 ---
 
 fix: replace deprecated `ipykernel.comm.Comm` with `comm` module

.changeset/sixty-mirrors-buy.md

@@ -0,0 +1,5 @@
+---
+"anywidget": patch
+---
+
+fix: revert `watchfiles` to optional-dependency

README.md

@@ -25,7 +25,7 @@ Learn more in
 may be installed with `pip`:
 
 ```bash
-pip install anywidget
+pip install "anywidget[dev]"
 ```
 
 It is also available on

anywidget/_util.py

@@ -164,6 +164,27 @@ def get_repr_metadata() -> dict:
     return {_WIDGET_MIME_TYPE: {"colab": {"custom_widget_manager": {"url": url}}}}
 
 
+def _should_start_thread(path: pathlib.Path) -> bool:
+    if "site-packages" in path.parts:
+        # file is inside site-packages, likely not a local development install
+        return False
+
+    try:
+        import watchfiles  # noqa: F401
+    except ImportError:
+        import warnings
+
+        warnings.warn(
+            "anywidget: Live-reloading feature is disabled."
+            " To enable, please install the 'watchfiles' package.",
+            stacklevel=2,
+        )
+
+        return False
+
+    return True
+
+
 def try_file_contents(x: Any) -> FileContents | None:
     """Try to coerce x into a FileContents object."""
     if not isinstance(x, (str, pathlib.Path)):
@@ -175,11 +196,9 @@ def try_file_contents(x: Any) -> FileContents | None:
     with contextlib.suppress(OSError):
         maybe_path = pathlib.Path(maybe_path).resolve().absolute()
         if maybe_path.is_file():
-            # Start a watch thread if file is outside of site-packages
-            # (i.e., likely a development install)
             return FileContents(
                 path=maybe_path,
-                start_thread="site-packages" not in maybe_path.parts,
+                start_thread=_should_start_thread(maybe_path),
             )
 
     return None

docs/src/pages/blog/anywidget-02.md

@@ -13,7 +13,7 @@ _TL;DR: **anywidget** v0.2 brings modern web development to Jupyter. You can now
 use a **file path** to enable **anywidget**'s integrated Hot Module Replacement (HMR):_
 
 ```sh
-pip install --upgrade anywidget
+pip install --upgrade "anywidget[dev]"
 ```
 
 ```python
@@ -193,7 +193,7 @@ to allow for the special JSX syntax (e.g., `<App />`).
 To start using **anywidget** v0.2, upgrade your package using pip:
 
 ```sh
-pip install --upgrade anywidget
+pip install --upgrade "anywidget[dev]"
 ```
 
 I encourage you to explore the new features in **anywidget** v0.2 and experience the

docs/src/pages/en/getting-started.mdx

@@ -28,7 +28,7 @@ ecosystem, allowing your widget to run automatically in **Jupyter Notebooks**,
 ## Example
 
 ```
-pip install anywidget
+pip install "anywidget[dev]"
 ```
 
 ```python

pyproject.toml

@@ -17,7 +17,6 @@ dependencies = [
     "importlib-metadata ; python_version < '3.8'",
     "typing-extensions>=4.2.0",
     "psygnal>=0.8.1",
-    "watchfiles>=0.18.0",
 ]
 
 [project.optional-dependencies]
@@ -29,7 +28,8 @@ test = [
     "ruff",
 ]
 dev = [
-    "comm",
+    "comm>=0.1.0",
+    "watchfiles>=0.18.0",
 ]
 
 [project.urls]

tests/test_utils.py

@@ -120,3 +120,18 @@ def test_try_file_contents(tmp_path: pathlib.Path):
     file_contents = try_file_contents(bar)
     assert isinstance(file_contents, FileContents)
     assert file_contents._background_thread is None
+
+
+def test_try_file_contents_warns(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: pathlib.Path
+):
+    monkeypatch.setitem(sys.modules, "watchfiles", None)
+
+    foo = tmp_path / "foo.txt"
+    foo.write_text("foo")
+
+    with pytest.warns(UserWarning, match="anywidget:"):
+        file_contents = try_file_contents(foo)
+
+    assert isinstance(file_contents, FileContents)
+    assert file_contents._background_thread is None