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Python lint: Ruff rules for pylint and code complexity #525

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Python lint: Ruff rules for pylint and code complexity #525

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@cclauss cclauss commented Apr 15, 2025 •
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Add ruff rules for Pylint and McCabe cyclomatic code complexity.

% ruff check --select=C90,PL --statistics | sort -k2

 5	C901   	[ ] complex-structure
 1	PLC0414	[ ] useless-import-alias
19	PLR0402	[*] manual-from-import
 1	PLR0911	[ ] too-many-return-statements
 1	PLR0912	[ ] too-many-branches
 5	PLR0913	[ ] too-many-arguments
 1	PLR0915	[ ] too-many-statements
26	PLR2004	[ ] magic-value-comparison
 1	PLW1510	[*] subprocess-run-without-check
[*] 20 fixable with the `--fix` option (1 hidden fix can be enabled with the `--unsafe-fixes` option).
Found 60 errors.

Motivation and Context

Pylint checks for errors, enforces a coding standard, looks for code smells, and can suggest how code could be refactored.
McCabe detects functions with high complexity that are hard to understand and maintain.

The C90 and PLR091 rules enable the setting of upper limits on code complexity. If a contributor wants to raise these limits, that can lead to useful discussion in code reviews about why complexity needs to rise and maintainability needs to go down.

How Has This Been Tested?

Breaking Changes

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

Additional context

@cclauss cclauss force-pushed the ruff-rules-for-pylint branch from 8690e74 to 1d06973 Compare April 15, 2025 20:50
@ihrpr ihrpr added this to the r-05-25 milestone Apr 29, 2025
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ihrpr reviewed May 23, 2025
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Thank you for contributing to Python SDK!

  1. Please can you provide rationale for the specific numerical thresholds chosen
  2. Is implementing both C90 and PL linting rules simultaneously necessary?
  3. Please remove the widespread import style changes which aren't central to the linting goals

The subprocess check=False change is great, but should be submitted as a separate PR focused on that specific fix.

cclauss added a commit to cclauss/python-sdk that referenced this pull request May 23, 2025
@cclauss
Python lint: Ruff rule PLW1510 -- subprocess-run-without-check
b4758a8 
A subset of:
*  modelcontextprotocol#525

% `ruff check --select=PLW1510`
```
 1	PLW1510	[*] subprocess-run-without-check
```
https://docs.astral.sh/ruff/rules/subprocess-run-without-check
@cclauss cclauss mentioned this pull request May 23, 2025
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@cclauss cclauss force-pushed the ruff-rules-for-pylint branch from 1d06973 to 7628dcb Compare May 23, 2025 17:38
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cclauss commented May 23, 2025 •
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Please read the git commit when reviewing pull requests.

Please can you provide rationale for the specific numerical thresholds chosen

The C90 and PLR091 rules enable the setting of upper limits on code complexity. If a contributor wants to raise these limits, that can lead to useful discussion in code reviews about why complexity needs to rise and maintainability needs to go down.

The current code complexity determines the values set in this PR, with comments showing the recommended values. If you want to find complexity in the codebase, then lower any of these values by one and run ruff check. Failure to review and merge this pr has forced an increase in max-complexity, max-branches, max-returns, and max-statements. Putting C90 and PLR091 in the same PR makes sense because they both set upper limits on code complexity and maintainability.

- mccabe.max-complexity = 13  # Default is 10
- max-branches = 14    # Default is 12
- max-returns = 7      # Default is 6
- max-statements = 69  # Default is 50
+ mccabe.max-complexity = 24  # Default is 10
+ max-branches = 23    # Default is 12
+ max-returns = 13      # Default is 6
+ max-statements = 99  # Default is 50

I have the RUFF settings to ignore the pylint import rules PLC0414 and PLR0402.

@cclauss cclauss requested a review from ihrpr May 24, 2025 06:54
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