BugFix: napari does not start with Python v3.11.1: "ValueError: A distribution name is required."

[glichtner]

Description

Summary

napari does not start with Python 3.11.1 as importlib.metadata.Distribution raises ValueError: A distribution name is required.

Solution

The solution is to add an additional check for empty app_module in running_as_bundled_app() and return False if it is empty.

Details

• The from_name() function of Python's importlib.metadata.Distribution has been changed to check for the emptiness of the name parameter in Python 3.11.1 (vs 3.11.0; see updated version here vs previous version ).
• An empty name will now throw a ValueError, preventing napari from starting with Python v3.11.1, as napari.utils.misc.running_as_bundled_app() calls importlib.metadata.metadata() with an empty app_module parameter when running as stand-alone or using pytest.
• This app_module parameter is directly relayed to Distribution.from_name, resulting in the following error when running napari with Python 3.11.1 (Ubuntu 22.04.1 LTS; napari pypi release 0.4.17 and github commit 54c1dbf )

Traceback (most recent call last):
  File "/home/glichtner/code/test/test/bin/napari", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/__main__.py", line 561, in main
    _run()
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/__main__.py", line 218, in _run
    from napari import Viewer, run
  File "<frozen importlib._bootstrap>", line 1231, in _handle_fromlist
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/_lazy.py", line 48, in __getattr__
    submod = import_module(
             ^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/viewer.py", line 8, in <module>
    from .components.viewer_model import ViewerModel
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/components/__init__.py", line 19, in <module>
    from .layerlist import LayerList
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/components/layerlist.py", line 9, in <module>
    from ..layers import Layer
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/layers/__init__.py", line 11, in <module>
    from .base import Layer
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/layers/base/__init__.py", line 1, in <module>
    from .base import Layer, no_op
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/layers/base/base.py", line 28, in <module>
    from ...utils.key_bindings import KeymapProvider
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/utils/key_bindings.py", line 46, in <module>
    from ..settings import get_settings
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/settings/__init__.py", line 6, in <module>
    from ._napari_settings import CURRENT_SCHEMA_VERSION, NapariSettings
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/settings/_napari_settings.py", line 14, in <module>
    from ._plugins import PluginsSettings
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/settings/_plugins.py", line 27, in <module>
    class PluginsSettings(EventedSettings):
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/settings/_plugins.py", line 75, in PluginsSettings
    class NapariConfig:
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/settings/_plugins.py", line 83, in NapariConfig
    if running_as_bundled_app() or running_as_constructor_app():
       ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/glichtner/code/test/test/lib/python3.11/site-packages/napari/utils/misc.py", line 67, in running_as_bundled_app
    metadata = importlib.metadata.metadata(app_module)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/importlib/metadata/__init__.py", line 998, in metadata
    return Distribution.from_name(distribution_name).metadata
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/importlib/metadata/__init__.py", line 561, in from_name
    raise ValueError("A distribution name is required.")
ValueError: A distribution name is required.

• The error occurs with Python v3.11.1 on macos, windows and linux (as indicated by my napari's plugin test runs: https://github.com/glichtner/napari-pystackreg/actions/runs/3923263123).
• I have tested the fix on Ubuntu 22.04.1 LTS

Type of change

• Bug-fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

References

How has this been tested?

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• example: all tests pass with my change
• example: I check if my changes works with both PySide and PyQt backends
  as there are small differences between the two Qt bindings.

Final checklist:

• My PR is the minimum possible work for the desired functionality
• [] I have commented my code, particularly in hard-to-understand areas
• [] I have made corresponding changes to the documentation
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[psobolewskiPhD]

Thanks for the contribution!
🙏
I've activated CI and requested reviews from some smart folks!

[codecov]

Codecov Report

Merging #5482 (1b5ae32) into main (6d27f81) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5482      +/-   ##
==========================================
- Coverage   89.40%   89.35%   -0.06%     
==========================================
  Files         609      609              
  Lines       51146    51148       +2     
==========================================
- Hits        45729    45705      -24     
- Misses       5417     5443      +26     

Impacted Files	Coverage Δ
napari/utils/misc.py	81.89% <100.00%> (+0.15%)	⬆️
napari/_tests/test_draw.py	36.84% <0.00%> (-63.16%)	⬇️
napari/components/experimental/chunk/_pool.py	85.71% <0.00%> (-7.94%)	⬇️
napari/_qt/widgets/qt_color_swatch.py	71.54% <0.00%> (-3.26%)	⬇️
napari/utils/interactions.py	72.64% <0.00%> (-2.84%)	⬇️
napari/utils/info.py	81.91% <0.00%> (-2.13%)	⬇️
napari/components/_tests/test_layer_slicer.py	97.98% <0.00%> (-1.21%)	⬇️
napari/_qt/qt_event_loop.py	80.27% <0.00%> (-0.69%)	⬇️
napari/_qt/dialogs/qt_package_installer.py	81.81% <0.00%> (+0.39%)	⬆️
napari/utils/theme.py	94.04% <0.00%> (+0.59%)	⬆️
... and 1 more

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[Czaki]

PR related to this PR: #5439,

EDIT. IT will be nice to add some CI run for python 3.11 to our matrix. Without this we do not know if it is the only bug in 3.11 env.

[jaimergp]

This LGTM, but I have a question: under what circumstances is __package__ set to None?

[Czaki]

start 24h clock

This LGTM, but I have a question: under what circumstances is __package__ set to None?

I do not know, but it is present for a long time.

This what was changed is importlib.metadata.metadata that stops accepting None as the argument.