feat: lint configuration

[dmadisetti]

📝 Summary

Closes #8341

Adds configuration entry points changes for lint rule selection. Example:

[tool.marimo.lint]
ignore = ["MF004"]

[vercel]

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Mar 25, 2026 9:24pm

[Copilot]

Pull request overview

Adds configurable lint rule selection to marimo check via config ([tool.marimo.lint]) and CLI overrides, including support for per-file PEP 723 script metadata.

Changes:

• Introduces LintConfig (select/ignore) and a rule resolution mechanism (resolve_rules) to filter enabled lint rules.
• Threads lint_config through RuleEngine/Linter, adds CLI flags --select/--ignore, and supports PEP 723 file-level lint config merging.
• Adds unit/integration tests and a PEP 723 fixture file demonstrating [tool.marimo.lint].

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
marimo/_config/config.py	Adds LintConfig and exposes it under MarimoConfig/PartialMarimoConfig.
marimo/_lint/rule_selector.py	New rule selection implementation (select/ignore, prefix matching, sorted output).
marimo/_lint/rule_engine.py	Accepts lint_config in create_default() and filters rules accordingly.
marimo/_lint/linter.py	Wires lint_config into linting pipeline; adds per-file PEP 723 config support.
marimo/_lint/__init__.py	Adds resolve_lint_config() helper and passes lint config into run_check().
marimo/_cli/cli.py	Adds marimo check --select/--ignore options and passes resolved lint config into lint runner.
marimo/_ai/_tools/tools/lint.py	Notes TODO for applying session lint config in AI tool path.
tests/_lint/utils.py	Extends lint test helper to accept lint_config.
tests/_lint/test_rule_selector.py	Adds unit tests for rule selection behavior.
tests/_lint/test_lint_config_integration.py	Adds integration tests for config propagation + PEP 723 config reading.
tests/_lint/test_files/empty_cell_with_lint_config.py	Adds a PEP 723 metadata fixture demonstrating lint ignore configuration.

[Copilot]

_rule_engine_for_file() re-reads the file from disk via ScriptConfigManager even though the notebook contents were already read earlier in get_notebook_status(). For large repos this adds avoidable I/O per file. Consider parsing the PEP 723 block from load_result.contents (or passing the already-read text into ScriptConfigManager / a helper) so each file is only read once.

[codecov]

Bundle Report

Changes will increase total bundle size by 52 bytes (0.0%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
marimo-esm	25.59MB	52 bytes (0.0%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: marimo-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
assets/add-*.js	52 bytes	55.39kB	0.09%

[mscolnick]

nice work! I think (if not already done) it would be good to relax the empty cell rule to allow for comments. That was the main reason some people wanted configuration in the first place

[dmadisetti]

Thanks! Will followup