Makefile: Add lint-python which uses flake8

[cclauss]

Add a lint-python section to Makefile which pip installs flake8 and then executes:

• flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

Based on the experimentation done at https://travis-ci.com/nodejs/node/builds/79706150 - #21942

These tests currently exclude several directories and files:

• ./deps/npm/node_modules/node-gyp -- this repo currently has no automated testing
• ./deps/v8 -- contains several Python 3 only features such as async def
• ./src/noperfctr_macros.py -- contains "macros" which Python AST views as syntax errors
• ./src/notrace_macros.py -- contains "macros" which Python AST views as syntax errors
• ./tools -- contains "macros" which Python AST views as syntax errors

Hopefully this list can be reduced in future PRs with code modifications or the use of # noqa

E901,E999,F821,F822,F823 are the "showstopper" flake8 issues that can halt the runtime with a SyntaxError, NameError, etc. Most other flake8 issues are merely "style violations" -- useful for readability but they do not effect runtime safety.

• F821: undefined name name
• F822: undefined name name in __all__
• F823: local variable name referenced before assignment
• E901: SyntaxError or IndentationError
• E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[mscdex]

Is it not possible to bundle the linting library instead, like we do for eslint? That way we don't need to make system-wide changes (e.g. implicitly upgrading pip)?

[cclauss]

We could remove pip install —upgrade pip.

[cclauss]

@mscdex Does that last commit cover what you wanted or did I misunderstand your request?

Is the automated testing actually doing a "make lint"? If so, how do I view the output?

https://github.com/nodejs/node/runs/8932739 does not seem to contain the words "lint-python" or "flake8".

[targos]

This doesn't work on my system when not run as root:

OSError: [Errno 13] Permission denied: '/usr/lib/python2.7/site-packages/enum34-1.1.6.dist-info'
make[1]: *** [Makefile:1212: lint-python] Error 2

[cclauss]

Can you please try to add --user to the command and let me know if that works?

[targos]

👌 It works with --user

[targos]

Exclusions don't seem to work. I see many errors coming from deps/v8 in the output

[cclauss]

You see these errors where? Locally or in server-based build log?

[targos]

Locally, with make lint

[refack]

/cc @nodejs/python @nodejs/build-files

[refack]

1. Should split build code to a lint-python-build target, and add conditions (maype if $(shell python -m flake8 --version)
2. remove @ for traceability
3. IMHO setting should go into tox.ini and not stored in the Makefile

[refack]

see comments

[refack]

Hello @cclauss and thank you for the contribution 🥇
I made a few comments about the current implementation, but a part from that I'm not so sure this should run as part of the lint target (probably just the lint-ci target). We have a goal of optimizing the build time, for developers running locally, and separately on the CI cluster. The churn of the python files in the project is very low, so IMHO we could skip running this for every change...
Also we should simply exclude the whole of the /deps/ dir since those files are vendored in from 3rd party repos (almost everything) same for /tools/gyp/, as well as the /src/ and /lib/ dirs since they should not contain any python files.

[cclauss]

I implemented all suggestions except:

1. the if statement to jump from lint-python to lint-python-build (I could not get it right)
2. tox.ini because I am not a fan of another level of indirection and it robs the power to create a second pass thru flake8 with no --select but with --exit-zero on to find PEP8 violations.
3. Slight changes on the --excludes and a lint-python-all-files that has no --exclude

[richardlau]

lint-python: lint-python-build

?

[mscdex]

Does that last commit cover what you wanted or did I misunderstand your request?

What I meant was include the 'flake8' module in the repo, like we do with eslint for js files, to avoid having to install it system/user-wide (which I would find to be unexpected behavior).

[jasnell]

What's the status on this one?

[cclauss]

@mscdex it is expected behavior for Python package. "Vendoring in" is quite rare in the Python world.

@refack Could you please advise here. It has been three months...

[cclauss]

That is lots of approval... https://blog.github.com/2018-10-21-october21-incident-report

[refack]

@nodejs/build-files @nodejs/python PTAL
CI: https://ci.nodejs.org/job/node-test-pull-request/18041/

[refack]

Congratulations 🎉
Landed in 0c39290
@cclauss, thank you very much for the contribution.