ConfigurationError: Config file '{paths_to_try[0]}' does not exist when using serve -f -

[ToshY]

Problem

Using the following command, I'm passing the mkdocs.yml to the container.

cat mkdocs.yml | docker run --rm -i \
  -u $(id -u):$(id -g) \
  -p 8002:8000 \
  -v ${PWD}:/docs \
  ghcr.io/squidfunk/mkdocs-material:9.6 \
  serve -a 0.0.0.0:8000 -f -

Output

INFO    -  Building documentation...
INFO    -  Cleaning site directory
INFO    -  Documentation built in 0.63 seconds
INFO    -  [17:17:31] Watching paths for changes: 'docs/version/v1'
INFO    -  [17:17:31] Serving on http://0.0.0.0:8000/

Starting up works. Page is accesible.

Now after making changes, I get the error:

INFO    -  Building documentation...
INFO    -  Cleaning site directory
INFO    -  Documentation built in 0.63 seconds
INFO    -  [17:17:31] Watching paths for changes: 'docs/version/v1'
INFO    -  [17:17:31] Serving on http://0.0.0.0:8000/
INFO    -  [17:17:36] Detected file changes
INFO    -  Building documentation...
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/mkdocs/livereload/__init__.py", line 211, in _build_loop
    self.builder()
  File "/usr/local/lib/python3.11/site-packages/mkdocs/commands/serve.py", line 64, in builder
    config = get_config()
             ^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/mkdocs/commands/serve.py", line 43, in get_config
    config = load_config(
             ^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/mkdocs/config/base.py", line 360, in load_config
    with _open_config_file(config_file) as fd:
  File "/usr/local/lib/python3.11/contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/mkdocs/config/base.py", line 324, in _open_config_file
    raise exceptions.ConfigurationError(f"Config file '{paths_to_try[0]}' does not exist.")
mkdocs.exceptions.ConfigurationError: Config file '<stdin>' does not exist.
ERROR   -  [17:17:36] An error happened during the rebuild. The server will appear stuck until build errors are resolved.

[squidfunk]

Thanks for reporting. This is behavior of MkDocs. You're providing configuration to stdin (which MkDocs claims to support for serve), and MkDocs tries to reload the file. Here's a reproduction that does not use Docker or Material for MkDocs:

mkdocs new .
cat mkdocs.yml | mkdocs serve -f -

Then make a single change to docs/index.md, and you'll get:

INFO    -  Building documentation...
INFO    -  Cleaning site directory
INFO    -  Documentation built in 0.03 seconds
INFO    -  [14:54:34] Watching paths for changes: 'docs'
INFO    -  [14:54:34] Serving on http://127.0.0.1:8000/
INFO    -  [14:54:40] Detected file changes
INFO    -  Building documentation...
Traceback (most recent call last):
  File "/Users/squidfunk/Desktop/Reproductions/community/venv/lib/python3.12/site-packages/mkdocs/livereload/__init__.py", line 211, in _build_loop
    self.builder()
  File "/Users/squidfunk/Desktop/Reproductions/community/venv/lib/python3.12/site-packages/mkdocs/commands/serve.py", line 64, in builder
    config = get_config()
             ^^^^^^^^^^^^
  File "/Users/squidfunk/Desktop/Reproductions/community/venv/lib/python3.12/site-packages/mkdocs/commands/serve.py", line 43, in get_config
    config = load_config(
             ^^^^^^^^^^^^
  File "/Users/squidfunk/Desktop/Reproductions/community/venv/lib/python3.12/site-packages/mkdocs/config/base.py", line 360, in load_config
    with _open_config_file(config_file) as fd:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.12.9/Frameworks/Python.framework/Versions/3.12/lib/python3.12/contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "/Users/squidfunk/Desktop/Reproductions/community/venv/lib/python3.12/site-packages/mkdocs/config/base.py", line 324, in _open_config_file
    raise exceptions.ConfigurationError(f"Config file '{paths_to_try[0]}' does not exist.")
mkdocs.exceptions.ConfigurationError: Config file '<stdin>' does not exist.
ERROR   -  [14:54:41] An error happened during the rebuild. The server will appear stuck until build errors are resolved.

Thus, please report this to the maintainers of MkDocs.

[ToshY]

Good to know. I will go report it there instead. Thanks for taking your time 👍