ruff check --preview --select=E303

[cclauss]

As requested at:

• Ensure the ino we give to readdir matches the ino we give to stat #23139 (comment)

% ruff rule E303

too-many-blank-lines (E303)

Derived from the pycodestyle linter.

Fix is always available.

This rule is in preview and is not stable. The --preview flag is required for use.

What it does

Checks for extraneous blank lines.

Why is this bad?

PEP 8 recommends using blank lines as follows:

• No more than two blank lines between top-level statements.
• No more than one blank line between non-top-level statements.

Example

def func1():
    pass



def func2():
    pass

Use instead:

def func1():
    pass


def func2():
    pass

Typing stub files (.pyi)

The rule allows at most one blank line in typing stub files in accordance to the typing style guide recommendation.

Note: The rule respects the following isort settings when determining the maximum number of blank lines allowed between two statements:

• [lint.isort.lines-after-imports]: For top-level statements directly following an import statement.
• [lint.isort.lines-between-types]: For import statements directly following a from ... import ... statement or vice versa.

Options

• lint.isort.lines-after-imports
• lint.isort.lines-between-types

References

• PEP 8: Blank Lines
• Flake 8 rule
• Typing Style Guide

[sbc100]

Is there any way to have ruff check include E303 without adding these extra command line argument?

I'm just thinking for local development its nice to just run ruff check from time to time.

[cclauss]

Nope. We need to target using both --preview and --select=E303. Without --preview, E303 will not be tested. Without --select=E303 then ruff check --preview with our current ruff config in pyproject.toml returns:

Found 17355 errors.
[*] 497 fixable with the --fix option (221 hidden fixes can be enabled with the --unsafe-fixes option).

I chose this approach because running both commands one after the other will take a small fraction of one second.

[sbc100]

Ok that sounds like a reasonable solution for now. Can you add a comment explaining why this is needed? Is it simply that the ruff authors are still working on the E303 rule? Will it become stable at some point and we can remove this? Perhaps mention that in the comment?

[cclauss]

Will do… https://docs.astral.sh/ruff/preview

[cclauss]

TODO (cclauss): When ruff supports rule E303 without --preview, remove

1. lint.select E303
2. lint.explicit-preview-rules = true, and
3. lint.preview = true

[cclauss]

I reverted to the original solution. tool.ruff.lint.explicit-preview-rules would have been much easier to use and understand if it took a list of rules but it is just a bool so it invoked ruff rule F841 but only when tuple unpacking. Too confusing.