Smart code line length validation

[orsinium]

Rule request

Thesis

1. Validate that code line not longer than N chars. Looks like 89.5 chars is a convention for now (one, two).
2. Allow lines longer than N chars if the part after N chars contains only a string and optional comma.
3. Maybe, even such lines should be limited. For instance, not to get longer than 120 chars. However, this part can be validated by flake8 max-line-length without any effort from us.

Example:

d = {
  # it is ok
  'one': 'some really long message that goes beyond 90 chars',
}

Reasoning

Statements longer than 80 columns will be broken into sensible chunks, unless exceeding 80 columns significantly increases readability and does not hide information. <...> However, never break user-visible strings such as printk messages, because that breaks the ability to grep for them.

• linux coding style

I see a lot of Python code that does some awful breaks to fit long text messages into the project's line limit just because. However, it creates a lot of difficulties:

1. Difficult to grep.
2. Easy to miss a space on the string breaks.
3. It doesn't make code more readable at all, even decreases readability. In most cases, I don't care if the ending of an error message goes outside of my screen.

After all, it's good to relax a rule that looks not so reasonable in the modern world:

Go has no line length limit. Don't worry about overflowing a punched card.

[sobolevn]

Yes, there are issues with some long lines:

• URL that are long
• Text messages

[orsinium]

Yes, exactly. Sometimes it helps to move it into a separate var:

msg = "something went really-really wrong"
raise SomeReallyEnterpriseClassicJavaNameError(msg)

But sometimes the message itself is too long.

[ruwaid4]

Hi again, me and my friend would like to try and take on this issue. What's the believed difficulty level for this one?

[sobolevn]

This one is not clear to me yet. You can select any issue from: https://github.com/wemake-services/wemake-python-styleguide/milestone/16

It would be easier 🙂

[orsinium]

flake8-bugbear has B950: line too long rule.

https://github.com/PyCQA/flake8-bugbear/blob/5e541a8e7036cb43c97c86295eeb2c6498980f01/bugbear.py#L44-L52

The idea is a bit similar: to relax a bit line length limit.

[orsinium]

Also, if the line-length limit is violated by # noqa... or # pragma... comment. You can't just move it on a separate line, the linter says where the comment must be put.

UPD: also, # {N,W,E,R}: comments from pytest-mypy-testing and pytest-mypy-plugins

[orsinium]

The related task for a go linter: walle/lll#11

[orsinium]

I decided to experiment with it a bit and made a separate small plugin:
https://github.com/orsinium-labs/flake8-length

[sobolevn]

Awesome! 👍