Error with running black 21.8b0 on python 3.6: cannot import name 'TypeGuard'

[ilsurih]

Describe the bug

After 21.8b0 was released our py-3.6 CI started failing with the following error:
ImportError: cannot import name 'TypeGuard'

To Reproduce

Not sure what exactly can help to reproduce this. Comparing to previous run, the only changed version is black and importlib-metadata.

Expected behavior

NA, as it fails on startup

Environment (please complete the following information):
Using tox to install env, these are test dependencies:

flake8
flake8-black
flake8-bugbear
flake8-copyright
flake8-isort
pep8-naming

• Version:3.6
• OS and Python version: [Linux/Python 3.6] TBD

Does this bug also happen on main?

NA, as it is fails on startup

Additional context

typing-extensions released new patch for issue listed in changelog of 8b0: python/typing#865

Collecting typing-extensions>=3.6.4
  Downloading typing_extensions-3.10.0.2-py3-none-any.whl (26 kB)

Our CI doesn't lock version, however build is still failing

Current workaround is to lock to 7b0 and build passes with that version

[felix-hilden]

I suspect this was submitted in error, so I'll close it. But feel free to edit the content and respond if you did have a bug that was bothering you!

---

Edit: I see you just changed the title, I'm following along if you have any details!

[MarcoGorelli]

@ilsurih how did you install black? pip install black should come with typing-extensions 3.10.x, which should have TypeGuard

[ilsurih]

@MarcoGorelli, @felix-hilden, sorry, submitted by mistake, let me finish writing description details

[ilsurih]

@MarcoGorelli, we are using tox to run tests and it installs typing-extensions 3.10.0.2

[MarcoGorelli]

I can't reproduce this on Python3.6 with typing-extensions 3.10.0.2, black 21.8b0, and the flake8 plugins you listed. Could you share your tox.ini file?

[ilsurih]

I noticed that we are locking typing-extensions~=3.7.4 (comes from marshmallow-dataclass) and even if it installs latest version with black, it later reinstalls it back to 3.7.4.3:

2021-08-31T10:54:49.4395718Z Collecting typing-extensions>=3.6.4
2021-08-31T10:54:49.4544681Z Downloading typing_extensions-3.10.0.2-py3-none-any.whl (26 kB)
...
2021-08-31T10:54:58.3922311Z lint-check installdeps: :ART:-...
2021-08-31T10:56:44.0560819Z lint-check installed: ...black==21.8b0,...,typeguard==2.12.1,typing-extensions==3.7.4.3...

So it appears 21.8b0 introduced a change that is no longer compatible with typing-extensions==3.7.4.3

[MarcoGorelli]

Yes, 21.8b0 uses TypeGuard - that's why typing-extensions>=3.10.0.0 is required