Black reformat

[zerolab]

Fixes #6056

This PR

• adds black to pre-commit configuration, testing_extras in setup.py, Makefile and lint job in CircleCI configuration.
• updates flake8 and isort configuration to use the black profile. Note that I left isort at the current version (5.6.4) as profiles support was added in 5.0.0
• updates editorconfig with the new line length (88) for py files
• updates python guidelines in docs

and finally, reformats with black (and fixes E501 - line length for updated flake8 config)

Rebasing PRs

Based on the methodology from #7908

# Make a copy of your branch
git branch save/my-existing-branch my-existing-branch
# Make sure you have the latest `main` from Wagtail
git checkout main
git pull upstream main
# Rebase your work onto the version of `main` right before
# we reformatted the whole project with Prettier –
# you can then resolve conflicts that would have been present anyway.
git rebase 6dae6e5d07059a12ec70deec6510b041582a88e7
# Install dependencies
## pre-commit via pip and initialize
pip install pre-commit && pre-commit install
## black/flake8 directly via Wagtail's testing dependencies (either in a VM or a virtual environment)
pip install -e .[testing]
# Run black and flake8
## with pre-commit
pre-commit run black && pre-commit run flake8
## without
black . && flake8 .
# Rebase again, this time with the reformatting as the base,
# always preserving your changes in case of conflicts, and automatically linting and reformatting.
## pre-commit
git rebase \
  --strategy-option=theirs \
  --exec '(pre-commit run black --all-files || true) && git add . && git commit --amend --no-edit --no-verify' \
  d10f15e55806c6944827d801cd9c2d53f5da4186
## or, directly
git rebase \
  --strategy-option=theirs \
  --exec '(black --target-version py37 . || true) && git add . && git commit --amend --no-edit --no-verify' \
  d10f15e55806c6944827d801cd9c2d53f5da4186
# Lint again, this should not show any errors
## using precommit
pre-commit run --all-files
## or, directly
black --target-version py37 .
flake8 .
# Finally rebase onto the latest version from Wagtail main, as per usual.
git rebase main

To-Do

• update https://github.com/wagtail/wagtail/blob/main/.git-blame-ignore-revs after merge (f16d29e)
• replace the-commit-after-reformatting with the reformat commit sha after merge

[squash-labs]

Manage this branch in Squash

Test this branch here: https://zerolabchoreblack-configuratio-j43q0.squash.io

[atombrella]

Please remember to add the commit hash to https://github.com/wagtail/wagtail/blob/main/.git-blame-ignore-revs once merged

[zerolab]

Absolutely. As well as instructions for reading WIP PRs

[thibaudcolas]

I have a couple questions about the configuration and want to suggest we don’t enforce line lengths with flake8 in addition to black, since it doesn’t seem to be very useful.

In addition, should we use black’s --target-version py37? Trying it out, it was additionally adding trailing commas in a few files.

Finally, with Wagtail having lots of Python code in its documentation, I was wondering if we should run black there (see blackdoc) for consistency? Either in this PR or as a separate follow-up.

[thibaudcolas]

Looking good! I get no extra reformatting locally, and it seems like all linting is passing in CI. Note I only reviewed some of the code changes a few commits ago – haven’t re-reviewed the reformatting changes since.

[zerolab]

Merged in d10f15e + parents.
Changelog - 716bf92
.git-blame-ignore-revs - f16d29e

[lb-]

Great stuff @zerolab

[gasman]

@zerolab Please can we put the 'rebasing PRs' instructions somewhere more easily findable (a wiki page perhaps), and ensure they're fixed and updated as necessary? (one-commit-before-reformatting doesn't appear to be defined, and I'm not sure it makes sense to rebase on top of it while main is checked out...)

[gasman]

@zerolab Please can we put the 'rebasing PRs' instructions somewhere more easily findable (a wiki page perhaps), and ensure they're fixed and updated as necessary? (one-commit-before-reformatting doesn't appear to be defined, and I'm not sure it makes sense to rebase on top of it while main is checked out...)

Never mind - piecing it together from the instructions on #6059 (comment) now. Will create that wiki page when I'm done :-)

[zerolab]

Gah, I missed one-commit-before-reformatting. Added in the code block in the first comment (the sha was 6dae6e5d07059a12ec70deec6510b041582a88e7)