Add an error message when both myst_nb and myst_parser included in extensions#713
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frankier wants to merge 1 commit intoexecutablebooks:mainfrom
Open
Add an error message when both myst_nb and myst_parser included in extensions#713frankier wants to merge 1 commit intoexecutablebooks:mainfrom
frankier wants to merge 1 commit intoexecutablebooks:mainfrom
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bsipocz
requested changes
Apr 13, 2026
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bsipocz
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bsipocz
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While this looks good on the diff level, I don't see it actually having any effect locally if you change the order of the extensions in the config file.
conf.py:
extensions = [
'myst_nb',
'myst_parser',
]
traceback:
Extension error!
Versions
========
* Platform: darwin; (macOS-12.5.1-arm64-arm-64bit)
* Python version: 3.12.1 (CPython)
* Sphinx version: 9.1.0
* Docutils version: 0.21.2
* Jinja2 version: 3.1.6
* Pygments version: 2.18.0
Last Messages
=============
None.
Loaded Extensions
=================
None.
Traceback
=========
Traceback (most recent call last):
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/cmd/build.py", line 414, in build_main
app = Sphinx(
^^^^^^^
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/application.py", line 299, in __init__
self.setup_extension(extension)
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/application.py", line 505, in setup_extension
self.registry.load_extension(self, extname)
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/registry.py", line 569, in load_extension
metadata = setup(app)
^^^^^^^^^^
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/myst_parser/__init__.py", line 13, in setup
setup_sphinx(app, load_parser=True)
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/myst_parser/sphinx_ext/main.py", line 37, in setup_sphinx
app.add_source_suffix(".md", "markdown")
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/application.py", line 1726, in add_source_suffix
self.registry.add_source_suffix(suffix, filetype, override=override)
File "/Users/bsipocz/.pyenv/versions/3.12.1/lib/python3.12/site-packages/sphinx/registry.py", line 350, in add_source_suffix
raise ExtensionError(__('source_suffix %r is already registered') % suffix)
sphinx.errors.ExtensionError: source_suffix '.md' is already registered
The full traceback has been saved in:
/var/folders/9s/070g0pd502q70k3gffpxv8km0000gq/T/sphinx-err-cmvshwrb.log
To report this error to the developers, please open an issue at <https://github.com/sphinx-doc/sphinx/issues/>. Thanks!
Please also report this if it was a user error, so that a better error message can be provided next time.
| if "myst_parser" in app.extensions: | ||
| raise ValueError( | ||
| "Cannot load both myst_nb and myst_parser Sphinx extensions " | ||
| "-- load only myst_nb since it includes myst_parser" |
Member
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Maybe rephrase to be more clear about the action item:
Suggested change
| "-- load only myst_nb since it includes myst_parser" | |
| "-- please only list only myst_nb as an extension in your configuration since it includes myst_parser." |
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Fixes #653