mcore-linting-and-formatting

name	mcore-linting-and-formatting
description	Linting and formatting for Megatron-LM. Covers running autoformat.sh, tools (ruff, black, isort, pylint, mypy), and code style rules.
license	Apache-2.0
when_to_use	Running linting or autoformat; fixing style violations before a PR; 'pre-commit fails', 'ruff error', 'isort', 'mypy', 'style violation', 'how do I format', 'autoformat.sh'.
metadata	{"author":"Philip Petrakian <[e-mail]>"}

Linting and Formatting

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Running the Formatter

Run before opening a PR:

# Check mode (no changes applied)
BASE_REF=main CHECK_ONLY=true SKIP_DOCS=false bash tools/autoformat.sh

# Fix mode
BASE_REF=main CHECK_ONLY=false bash tools/autoformat.sh

Tools invoked: black, isort, pylint, ruff, mypy.

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Import Ordering

After editing imports in any Python files, always run uv run isort on those files before committing:

uv run isort <file1>.py <file2>.py

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Setting Up the Linting Group

Inside the container:

uv sync --locked --only-group linting

This installs ruff, black, isort, pylint — the same tools used by tools/autoformat.sh and CI's linting job.

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Code Style Rules

• Type hints: required on all public API functions. Use X | None, not Optional[X].
• Docstrings: Google-style on all public classes and functions.
• Naming: follow Python conventions — snake_case for functions and variables, PascalCase for classes.
• Line length: 119 characters (configured in pyproject.toml).
• No bare except: always catch specific exception types.