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@cclauss cclauss commented Apr 15, 2025

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
ihrpr
ihrpr previously requested changes 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
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 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

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. To find complexity in the codebase, just 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
+ max-statements = 102  # 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
@cclauss cclauss force-pushed the ruff-rules-for-pylint branch from 191f41b to 1596aca Compare June 3, 2025 12:41
@cclauss cclauss requested a review from Kludex June 3, 2025 12:43
gspencergoog pushed a commit to gspencergoog/mcp-python-sdk that referenced this pull request Jul 29, 2025
This replaces absolute URLs with paths, links the "Roots" column header,
and moves anchor definitions for the table header links to the top for
organizational purposes.

Closes modelcontextprotocol#525

Co-authored-by: Andrew Qu <[email protected]>
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Apologies for the delay in coming back to this.

It would be great if we could address the issues introduced by the new lint rules instead of adding linter overrides.

Happy to come back to this quickly if you have the capacity to take a stab at this?

@felixweinberger felixweinberger added the needs more work Not ready to be merged yet, needs additional changes. label Sep 5, 2025
@cclauss cclauss requested a review from a team September 5, 2025 13:37
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While I'm not a fan of ignoring ruff rules, in this case I believe it is justified given we're actually sharpening our lint rules overall and simply making explicit what we were previously implicitly ignoring.

Therefore I think we should land this in the interest of managing growing complexity on the Python SDK.

I've also created an issue for our v2 release where ideally we'd get rid of all ignores here.

"PL", # Pylint
"UP", # pyupgrade
]
ignore = ["PERF203", "PLC0415", "PLR0402"]
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"PLC0415" and "PLR0402" are newly added.

I'm assuming that's because we've added to the selection of tools above causing new lint errors to appear that we previously were ignoring by omission?

If so I'm OK with this trade-off in the short term to have a bit more manageable complexity.

[tool.ruff.lint.per-file-ignores]
"__init__.py" = ["F401"]
"tests/server/fastmcp/test_func_metadata.py" = ["E501"]
"tests/shared/test_progress_notifications.py" = ["PLW0603"]
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Not my favorite solution, but assuming the same thing applies as above - we have this code already, we were just ignoring it by omission.

PLW0603

@felixweinberger felixweinberger dismissed ihrpr’s stale review September 5, 2025 14:19

Requested changes have been addressed

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@cclauss thank you for the contribution and apologies again for the delay!

@felixweinberger felixweinberger merged commit c47c767 into modelcontextprotocol:main Sep 5, 2025
35 of 36 checks passed
@cclauss cclauss deleted the ruff-rules-for-pylint branch September 5, 2025 14:50
rbehal pushed a commit to gumloop/gumloop-mcp that referenced this pull request Sep 25, 2025
* Add regression test for stateless request memory cleanup (modelcontextprotocol#1140)

* Implement RFC9728 - Support WWW-Authenticate header by MCP client (modelcontextprotocol#1071)

* Add streamable HTTP starlette example to Python SDK docs (modelcontextprotocol#1111)

* fix markdown error in README in main (modelcontextprotocol#1147)

* README - replace code snippets with examples - add lowlevel to snippets (modelcontextprotocol#1150)

* README - replace code snippets with examples - streamable http (modelcontextprotocol#1155)

* chore: don't allow users to create issues outside the templates (modelcontextprotocol#1163)

* Tests(cli): Add coverage for helper functions (modelcontextprotocol#635)

* Docs: Update CallToolResult parsing in README (modelcontextprotocol#812)

Co-authored-by: Felix Weinberger <[email protected]>

* docs: add pre-commit install guide on CONTRIBUTING.md (modelcontextprotocol#995)

Co-authored-by: Felix Weinberger <[email protected]>

* fix flaky fix-test_streamablehttp_client_resumption test (modelcontextprotocol#1166)

* README - replace code snippets with examples -- auth examples (modelcontextprotocol#1164)

* Support falling back to OIDC metadata for auth (modelcontextprotocol#1061)

* Add CODEOWNERS file for sdk (modelcontextprotocol#1169)

* fix flaky test test_88_random_error (modelcontextprotocol#1171)

* Make sure `RequestId` is not coerced as `int` (modelcontextprotocol#1178)

* Fix: Replace threading.Lock with anyio.Lock for Ray deployment compatibility (modelcontextprotocol#1151)

* fix: fix OAuth flow request object handling (modelcontextprotocol#1174)

* update codeowners group (modelcontextprotocol#1191)

* fix: perform auth server metadata discovery fallbacks on any 4xx (modelcontextprotocol#1193)

* server: skip duplicate response on CancelledError (modelcontextprotocol#1153)

Co-authored-by: ihrpr <[email protected]>

* Unpack settings in FastMCP (modelcontextprotocol#1198)

* chore: Remove unused prompt_manager.py file (modelcontextprotocol#1229)

Co-authored-by: Tapan Chugh <[email protected]>

* Improved supported for ProtectedResourceMetadata (modelcontextprotocol#1235)

Co-authored-by: Paul Carleton <[email protected]>

* chore: Remove unused variable notification_options (modelcontextprotocol#1238)

* Improve README around the Context object (modelcontextprotocol#1203)

* fix: allow to pass `list[str]` to `token_endpoint_auth_signing_alg_values_supported` (modelcontextprotocol#1226)

* Remove strict validation on `response_modes_supported` member of `OAuthMetadata` (modelcontextprotocol#1243)

* Add pyright strict mode on the whole project (modelcontextprotocol#1254)

* Consistent casing for default headers Accept and Content-Type (modelcontextprotocol#1263)

* Update dependencies and fix type issues (modelcontextprotocol#1268)

Co-authored-by: Marcelo Trylesinski <[email protected]>

* fix: prevent async generator cleanup errors in StreamableHTTP transport (modelcontextprotocol#1271)

Co-authored-by: David Soria Parra <[email protected]>

* chore: uncomment .idea/ in .gitignore (modelcontextprotocol#1287)

Co-authored-by: Claude <[email protected]>

* docs: clarify streamable_http_path configuration when mounting servers (modelcontextprotocol#1172)

* feat: Add CORS configuration for browser-based MCP clients (modelcontextprotocol#1059)

Co-authored-by: Marcelo Trylesinski <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>

* Added Audio to FastMCP (modelcontextprotocol#1130)

* fix: avoid uncessary retries in OAuth authenticated requests (modelcontextprotocol#1206)

Co-authored-by: Felix Weinberger <[email protected]>

* Add PATHEXT to default STDIO env vars in windows (modelcontextprotocol#1256)

* fix: error too many values to unpack (expected 2) (modelcontextprotocol#1279)

Signed-off-by: San Nguyen <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>

* SDK Parity: Avoid Parsing Server Response for non-JsonRPCMessage Requests (modelcontextprotocol#1290)

* types: Setting default value for method: Literal (modelcontextprotocol#1292)

* changes structured temperature to not deadly (modelcontextprotocol#1328)

* Update simple-resource example to use non-deprecated read_resource return type (modelcontextprotocol#1331)

Co-authored-by: Claude <[email protected]>

* docs: Update README to include link to API docs for modelcontextprotocol#1329 (modelcontextprotocol#1330)

* Allow ping requests before initialization (modelcontextprotocol#1312)

* Python lint: Ruff rules for pylint and code complexity (modelcontextprotocol#525)

* Fix context injection for resources and prompts (modelcontextprotocol#1336)

* fix(fastmcp): propagate mimeType in resource template list (modelcontextprotocol#1186)

Co-authored-by: Felix Weinberger <[email protected]>

* fix: allow elicitations accepted without content (modelcontextprotocol#1285)

Co-authored-by: Olivier Schiavo <[email protected]>

* Use --frozen in pre-commit config (modelcontextprotocol#1375)

* Return HTTP 403 for invalid Origin headers (modelcontextprotocol#1353)

* Add test for ProtectedResourceMetadataParsing (modelcontextprotocol#1236)

Co-authored-by: Paul Carleton <[email protected]>
Co-authored-by: Marcelo Trylesinski <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>

* Fastmcp logging progress example (modelcontextprotocol#1270)

Co-authored-by: Felix Weinberger <[email protected]>

* feat: add paginated list decorators for prompts, resources, and tools (modelcontextprotocol#1286)

Co-authored-by: Claude <[email protected]>

* Remove "unconditionally" from conditional description (modelcontextprotocol#1289)

* Use streamable-http consistently in examples (modelcontextprotocol#1389)

* feat: Add SDK support for SEP-1034 default values in elicitation schemas (modelcontextprotocol#1337)

Co-authored-by: Tapan Chugh <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>

* Implementation of SEP 973 - Additional metadata + icons support (modelcontextprotocol#1357)

* Merge upstream/main with custom filtering

---------

Signed-off-by: San Nguyen <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>
Co-authored-by: yurikunash <[email protected]>
Co-authored-by: Pamela Fox <[email protected]>
Co-authored-by: Inna Harper <[email protected]>
Co-authored-by: Marcelo Trylesinski <[email protected]>
Co-authored-by: Ian Davenport <[email protected]>
Co-authored-by: Dagang Wei <[email protected]>
Co-authored-by: Felix Weinberger <[email protected]>
Co-authored-by: Stanley Law <[email protected]>
Co-authored-by: Luca Chang <[email protected]>
Co-authored-by: leweng <[email protected]>
Co-authored-by: Clare Liguori <[email protected]>
Co-authored-by: lukacf <[email protected]>
Co-authored-by: ihrpr <[email protected]>
Co-authored-by: Tapan Chugh <[email protected]>
Co-authored-by: Tapan Chugh <[email protected]>
Co-authored-by: Yann Jouanin <[email protected]>
Co-authored-by: Paul Carleton <[email protected]>
Co-authored-by: Sreenath Somarajapuram <[email protected]>
Co-authored-by: Omer Korner <[email protected]>
Co-authored-by: joesavage-silabs <[email protected]>
Co-authored-by: Gregory L <[email protected]>
Co-authored-by: David Soria Parra <[email protected]>
Co-authored-by: Moustapha Ebnou <[email protected]>
Co-authored-by: Max Isbey <[email protected]>
Co-authored-by: Claude <[email protected]>
Co-authored-by: Jerome <[email protected]>
Co-authored-by: xavier <[email protected]>
Co-authored-by: keurcien <[email protected]>
Co-authored-by: Tim Esler <[email protected]>
Co-authored-by: San Nguyen <[email protected]>
Co-authored-by: Justin Wang <[email protected]>
Co-authored-by: jess <[email protected]>
Co-authored-by: Peter Alexander <[email protected]>
Co-authored-by: Reid Geyer <[email protected]>
Co-authored-by: Eleftheria Stein-Kousathana <[email protected]>
Co-authored-by: Christian Clauss <[email protected]>
Co-authored-by: pchoudhury22 <[email protected]>
Co-authored-by: owengo <[email protected]>
Co-authored-by: Olivier Schiavo <[email protected]>
Co-authored-by: Steve Billings <[email protected]>
Co-authored-by: Mike Salvatore <[email protected]>
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