lastlint: LaTeX strict linter

A linter for Evan Chen's LaTeX style guide.

Usage

Pre-commit hook

Add to your .pre-commit-config.yaml:

repos:
  - repo: https://github.com/cjquines/lastlint
    rev: v0.6.0 # x-release-please-version
    hooks:
      - id: lastlint-fix

To only report errors rather than auto-fixing them, use the lastlint hook id.

Standalone

Install from PyPI. Using uv (recommended):

uv tool install lastlint
lastlint path/to/file.tex another.tex

To run without installing: uvx lastlint path/to/file.tex. With pip: pip install lastlint.

Multiple files are accepted, and glob patterns are expanded.

Pass --fix to auto-fix supported rules in place.

Pass --ignore E001,E013 to skip both reporting and fixing.

On a terminal, output is grouped per file and colorized; when piped or redirected it uses a plain file:line:col: EXXX: message format parseable by editors. Force either mode with --color always or --color never (also honors NO_COLOR and FORCE_COLOR).

Editor

An optional language server exposes lastlint to compatible text editors. Install it with the lsp extra:

uv tool install 'lastlint[lsp]'
# or: pip install 'lastlint[lsp]'

The server lastlint-lsp, over stdio, publishes diagnostics and implements formatting, so format-on-save will auto-fix LaTeX files. Pass ignored rules through initializationOptions, e.g. {"ignore": ["E001", "E013"]}.

The setups below assume lastlint-lsp is globally installed. To skip a global install, replace the command with uvx --from 'lastlint[lsp]' lastlint-lsp.

vim.lsp.config('lastlint', {
  cmd = { 'lastlint-lsp' },
  filetypes = { 'tex', 'plaintex' },
  root_markers = { '.git' },
})
vim.lsp.enable('lastlint')

{
  "clients": {
    "lastlint": {
      "enabled": true,
      "command": ["lastlint-lsp"],
      "selector": "text.tex.latex"
    }
  }
}

(with-eval-after-load 'eglot
  (add-to-list 'eglot-server-programs
               '((latex-mode LaTeX-mode) . ("lastlint-lsp"))))

Suppression

Add an inline comment to skip rules on a single line:

This text has "intentional" quotes.  % lastlint: disable=E002

Rules

Fixable rules are marked with 🔧.

Rules not implemented:

• Rule 8 (balanced delimiters): hard to lint reliably.
• Rule 16 (variables in prose): requires natural-language understanding.

E001

E001 skips two kinds of unfixable long lines: those containing a URL (http:// or https://), and fully-commented lines (only whitespace before the %). Lines with a long trailing comment after real content are still flagged.

I recommend SemBr for automatically adding line breaks.

E004

E004 picks the right \dots variant from context (\dotsc after a comma, \dotsb after an operator) and leaves a \cdots unresolved when neither side determines spacing.

E013

E013 checks every env except a small denylist: document, center, quote, and the verbatim envs (asy, tikzpicture, verbatim, lstlisting, …). See NO_INDENT_ENVS in lastlint.py to adjust.

The --fix pads under-indented lines inside indent envs to 2 * depth spaces (already-correctly-indented or deeper lines are left alone), and converts leading tabs to 2 spaces each.

Development

pip install -e .[dev]
pytest