add --extensions cli arg for python filter

docs/cli.md

@@ -56,6 +56,13 @@ files:
 watchfiles --filter python 'pytest --lf' src tests
 ```
 
+If you want to watch additional file extensions beyond the default Python files (`.py`, `.pyx`, `.pyd`), you can use
+the `--extensions` flag:
+
+```bash title="Watching Python files and templates"
+watchfiles --filter python --extensions '.html,.jinja' 'pytest --lf' src tests
+```
+
 ## Help
 
 Run `watchfiles --help` for more options.

docs/cli_help.txt

@@ -1,4 +1,5 @@
 usage: watchfiles [-h] [--ignore-paths [IGNORE_PATHS]]
+                  [--extensions [EXTENSIONS]]
                   [--target-type [{command,function,auto}]]
                   [--filter [FILTER]] [--args [ARGS]] [--verbose]
                   [--non-recursive] [--verbosity [{warning,info,debug}]]
@@ -28,6 +29,8 @@ options:
   -h, --help            show this help message and exit
   --ignore-paths [IGNORE_PATHS]
                         Specify directories to ignore, to ignore multiple paths use a comma as separator, e.g. "env" or "env,node_modules"
+  --extensions [EXTENSIONS]
+                        Specify extra extensions to watch, to specify multiple extensions use a comma as separator, e.g. ".jinja" or ".html,.jinja"
   --target-type [{command,function,auto}]
                         Whether the target should be intercepted as a shell command or a python function, defaults to "auto" which infers the target type from the target string
   --filter [FILTER]     Which files to watch, defaults to "default" which uses the "DefaultFilter", "python" uses the "PythonFilter", "all" uses no filter, any other value is interpreted as a python function/class path which is imported

tests/test_cli.py

@@ -59,6 +59,35 @@ def test_ignore_paths(mocker, tmp_work_path):
     )
 
 
+def test_extensions(mocker, tmp_work_path):
+    mocker.patch('watchfiles.cli.sys.stdin.fileno')
+    mocker.patch('os.ttyname', return_value='/path/to/tty')
+    mock_run_process = mocker.patch('watchfiles.cli.run_process')
+    cli(
+        '--extensions',
+        '.html,.jinja',
+        '--filter',
+        'python',
+        'os.getcwd',
+        '.',
+    )
+    mock_run_process.assert_called_once_with(
+        Path(str(tmp_work_path)),
+        target='os.getcwd',
+        target_type='function',
+        watch_filter=(
+            IsInstance(PythonFilter)
+            & HasAttributes(extensions=('.py', '.pyx', '.pyd', '.html', '.jinja'), _ignore_paths=())
+        ),
+        debug=False,
+        grace_period=0,
+        sigint_timeout=5,
+        sigkill_timeout=1,
+        recursive=True,
+        ignore_permission_denied=False,
+    )
+
+
 class SysError(RuntimeError):
     pass
 

watchfiles/cli.py

@@ -57,6 +57,15 @@ def cli(*args_: str) -> None:
             'to ignore multiple paths use a comma as separator, e.g. "env" or "env,node_modules"'
         ),
     )
+    parser.add_argument(
+        '--extensions',
+        nargs='?',
+        type=str,
+        help=(
+            'Specify extra extensions to watch, '
+            'to specify multiple extensions use a comma as separator, e.g. ".jinja" or ".html,.jinja"'
+        ),
+    )
     parser.add_argument(
         '--target-type',
         nargs='?',
@@ -157,7 +166,11 @@ def cli(*args_: str) -> None:
         print(f'path "{e}" does not exist', file=sys.stderr)
         sys.exit(1)
 
-    watch_filter, watch_filter_str = build_filter(arg_namespace.filter, arg_namespace.ignore_paths)
+    watch_filter, watch_filter_str = build_filter(
+        arg_namespace.filter,
+        arg_namespace.ignore_paths,
+        arg_namespace.extensions,
+    )
 
     logger.info(
         'watchfiles v%s 👀  path=%s target="%s" (%s) filter=%s...',
@@ -195,19 +208,26 @@ def import_exit(function_path: str) -> Any:
 
 
 def build_filter(
-    filter_name: str, ignore_paths_str: Optional[str]
+    filter_name: str, ignore_paths_str: Optional[str], extensions_str: Optional[str] = None
 ) -> Tuple[Union[None, DefaultFilter, Callable[[Change, str], bool]], str]:
     ignore_paths: List[Path] = []
     if ignore_paths_str:
         ignore_paths = [Path(p).resolve() for p in ignore_paths_str.split(',')]
+    extensions: List[str] = []
+    if extensions_str:
+        extensions = [p for p in extensions_str.split(',')]
 
     if filter_name == 'default':
+        if extensions:
+            logger.warning('"--extensions" argument ignored as "all" filter was selected')
         return DefaultFilter(ignore_paths=ignore_paths), 'DefaultFilter'
     elif filter_name == 'python':
-        return PythonFilter(ignore_paths=ignore_paths), 'PythonFilter'
+        return PythonFilter(ignore_paths=ignore_paths, extra_extensions=extensions), 'PythonFilter'
     elif filter_name == 'all':
         if ignore_paths:
             logger.warning('"--ignore-paths" argument ignored as "all" filter was selected')
+        if extensions:
+            logger.warning('"--extensions" argument ignored as "all" filter was selected')
         return None, '(no filter)'
 
     watch_filter_cls = import_exit(filter_name)