Let flake8 check examples

[seisman]

flake8 would check for whitespace and lines >80 (both not caught by black in examples); currently flake8 is only used for pygmt, setup.py, and doc/conf.py.

Originally posted by @meghanrjones in #935 (comment)

Do we want flake8 to check all examples? Or do we want to limit line length in examples?

[seisman]

I don't like flake8 because it still doesn't support pyproject.toml (https://gitlab.com/pycqa/flake8/-/issues/428), but there are alternatives (e.g., https://flakehell.readthedocs.io/)

[weiji14]

Funny, I was looking at flakehell too last week. Dropping flake8 and switching to flakehell might allow us to get rid of the setup.cfg file I think. See also https://dev.to/bowmanjd/using-flake8-and-pyproject-toml-with-flakehell-1cn1

[seisman]

allow us to get rid of the setup.cfg file I think.

Yes!

[weiji14]

allow us to get rid of the setup.cfg file I think.

Yes!

See also https://stackoverflow.com/questions/44878600/is-setup-cfg-deprecated 😄. I think it should be safe to remove setup.cfg once (and if) we switch from flake8 to flakehell, but need to be extra careful in case it breaks some obscure Python packaging component.

[seisman]

Unfortunately, flakehell is no longer maintained.

[weiji14]

Unfortunately, flakehell is no longer maintained.

Oo, that was sudden. Guess we'll need to find or wait for an alternative.

Edit: Would autopep8 help with the original whitespace issue? It also support pyproject.toml according to https://github.com/hhatto/autopep8#pyprojecttoml

[seisman]

As I understand it, flake8 is still the most popular and widely-used tool for style checking. I think we should still use flake8, and (1) wait for the official pyproject.toml support (https://gitlab.com/pycqa/flake8/-/issues/428); (2) see if someone forks and maintains flakehell; (3) see if there are similar wrappers.

Back to the initial issue, I think we should let flake8 check the examples. It should also fix the trailing whitespace issue in #935.

To let flake8 check all examples, we need to change one single line in Makefile:

pygmt/Makefile

Line 11 in e057927

FLAKE8_FILES=$(PROJECT) setup.py doc/conf.py

and fix all warnings.

Before that, we need to discuss #962 first.

[seisman]

There is an "official" fork of flakehell at https://github.com/flakehell/flakehell.