[pylint] Implement misplaced-bare-raise (E0704)

[clemux]

Related issue: #970

Summary

What it does

This rule triggers an error when a bare raise statement is not in an except or finally block.

Why is this bad?

If raise statement is not in an except or finally block, there is no active exception to
re-raise, so it will fail with a RuntimeError exception.

Example

def validate_positive(x):
   if x <= 0:
       raise

Use instead:

def validate_positive(x):
   if x <= 0:
       raise ValueError(f"{x} is not positive")

Test Plan

Added unit test and snapshot.
Manually compared ruff and pylint outputs on pylint's tests.

References

• pylint documentation
• pylint implementation

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

[charliermarsh]

Thanks! Do you mind taking a look at some of the violations flagged in the ecosystem check, and seeing how they compare to pylint's behavior?

[clemux]

They are the same with pylint. I had to run pylint on each file though, I'm not sure what I'm doing wrong. For example, with pip:

(venv) clemux@Nardole:~/dev/pip/src$ pylint --disable=all --enable=misplaced-bare-raise .
(venv) clemux@Nardole:~/dev/pip/src$ pylint --disable=all --enable=misplaced-bare-raise pip/_internal/utils/misc.py
************* Module pip._internal.utils.misc
pip/_internal/utils/misc.py:157:4: E0704: The raise statement is not inside an except clause (misplaced-bare-raise)

------------------------------------------------------------------
Your code has been rated at 9.85/10 (previous run: 9.85/10, +0.00)

[clemux]

I wanted to use ruff_python_ast::helpers::RaiseStatementVisitor, but it doesn't store the raise statement itself.

It's only used in two rules, so maybe I can refactor that?

[charliermarsh]

Ah yeah -- can we change RaiseStatementVisitor to store Vec<&'a ast::StmtRaise>?

[clemux]

Shall I do that in a separate PR?

[charliermarsh]

I would be cool with including it here, but either is fine.

[clemux]

Not needed anymore, so I guess I won't touch RaiseStatementVisitor.