'Symbols' object has no attribute 'namedexpr_test'

[CuriousLearner]

Error: 'Symbols' object has no attribute 'namedexpr_test'

Operating system: OSX
Python version: 3.7
Black version: master
Does also happen on master:

To answer the last question, you have two options:

1. Use the online formatter at https://black.now.sh/?version=master, which will use the latest master branch.
2. Or run black on your machine:
   • create a new virtualenv (make sure it's the same Python version);
   • clone this repository;
   • run pip install -e .;
   • make sure it's sane by running python setup.py test; and
   • run black like you did last time.

I've run this using pre-commit hooks which gives the following error:

black....................................................................Failed
hookid: black

error: cannot format /Users/sanyamkhurana/work/mymp/mymp/maps/serializers.py: 'Symbols' object has no attribute 'namedexpr_test'
error: cannot format /Users/sanyamkhurana/work/mymp/mymp/maps/models.py: 'Symbols' object has no attribute 'namedexpr_test'
error: cannot format /Users/sanyamkhurana/work/mymp/mymp/maps/services.py: 'Symbols' object has no attribute 'namedexpr_test'
Oh no! 💥 💔 💥
1 file left unchanged, 3 files failed to reformat.

Note that if I install black using pip and try to reformat, these files are reformatted properly without any errors. The version I got from pip install is 19.3b0 which is working fine, but the master is breaking.

Here is my pre-commit-config.yaml

repos:
- repo: https://github.com/ambv/black
  rev: master
  hooks:
    - id: black
      language_version: python3.7

I've trimmed it for brevity. Please note that this was working fine 5 days earlier.

Please let me know if you need any more details.

[JelleZijlstra]

@zsol I'm guessing this is a result of the PEP 572 changes?

@CuriousLearner does this happen on all of your code or just on specific constructs?

[CuriousLearner]

@JelleZijlstra This happens for all the changes that are in the git working tree.

I've also tried to modify my pre-commit-hooks to use stable instead of a master like:

repos:
- repo: https://github.com/ambv/black
  rev: stable
  hooks:
    - id: black
      language_version: python3.7

and it seems that it is able to easily work for all those files that were failed by the master.

[zsol]

I'll take a look at this ASAP.

[zsol]

This is likely because the grammar in the cache is not regenerated, but it should be. @CuriousLearner can you try blowing away $HOME/.cache/black and rerunning the precommit hook from master?

[zsol]

We're relying on the fact that the cache is keyed by black.__version__, so this changes during a release. Maybe it should change per commit? I don't think we're making any reasonable precautions that would make cache-sharing between black versions in-between releases safe.

[JelleZijlstra]

If there is a good way to make the cache keyed by commit, that seems like the best solution.

Arguably people who run off master should be prepared for this sort of confusion, but we can hardly blame them for using master if we take so long between releases...

[zsol]

Pandas does it like this which looks promising on the surface until you open up _version.py :D ... although it's a generated file...

[CuriousLearner]

@zsol I couldn't find a cache for black in my home directory but I found one for pre-commit

$HOME/.cache/pre-commit so, I removed the entire cache, rebuilt my pre-commit hooks, and I was able to use the master version to succesfully reformat my files.

So, I think you're correct!