@astral-sh/ruff-wasm-bundler

Ruff WASM

⚠️ WARNING: This API is experimental and may change at any time

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An extremely fast Python linter and code formatter, written in Rust.

This is a WASM version of the Ruff API which can be used to lint/format Python in a browser environment.

There are multiple versions for the different wasm-pack targets. See here for more info on targets.

• Bundler
• Web
• Node.js

Usage

This example uses the wasm-pack web target and is known to work with Vite.

import init, { Workspace, type Diagnostic } from '@astral-sh/ruff-api';

const exampleDocument = `print('hello'); print("world")`

await init(); // Initializes WASM module

// These are default settings just to illustrate configuring Ruff
// Settings info: https://docs.astral.sh/ruff/settings
const workspace = new Workspace({
  'line-length': 88,
  'indent-width': 4,
  format: {
    'indent-style': 'space',
    'quote-style': 'double',
  },
  lint: {
    select: [
      'E4',
      'E7',
      'E9',
      'F'
    ],
  },
});

// Will contain 1 diagnostic code for E702: Multiple statements on one line
const diagnostics: Diagnostic[] = workspace.check(exampleDocument);

const formatted = workspace.format(exampleDocument);

Changelog

0.8.0

Check out the blog post for a migration guide and overview of the changes!

Breaking changes

See also, the "Remapped rules" section which may result in disabled rules.

• Default to Python 3.9

  Ruff now defaults to Python 3.9 instead of 3.8 if no explicit Python version is configured using ruff.target-version or project.requires-python (#13896)

• Changed location of pydoclint diagnostics

  pydoclint diagnostics now point to the first-line of the problematic docstring. Previously, this was not the case.

  If you've opted into these preview rules but have them suppressed using noqa comments in some places, this change may mean that you need to move the noqa suppression comments. Most users should be unaffected by this change.

• Use XDG (i.e. ~/.local/bin) instead of the Cargo home directory in the standalone installer

  Previously, Ruff's installer used $CARGO_HOME or ~/.cargo/bin for its target install directory. Now, Ruff will be installed into $XDG_BIN_HOME, $XDG_DATA_HOME/../bin, or ~/.local/bin (in that order).

  This change is only relevant to users of the standalone Ruff installer (using the shell or PowerShell script). If you installed Ruff using uv or pip, you should be unaffected.

• Changes to the line width calculation

  Ruff now uses a new version of the unicode-width Rust crate to calculate the line width. In very rare cases, this may lead to lines containing Unicode characters being reformatted, or being considered too long when they were not before (E501).

Removed Rules

The following deprecated rules have been removed:

• missing-type-self (ANN101)
• missing-type-cls (ANN102)
• syntax-error (E999)
• pytest-missing-fixture-name-underscore (PT004)
• pytest-incorrect-fixture-name-underscore (PT005)
• unpacked-list-comprehension (UP027)

Remapped rules

The following rules have been remapped to new rule codes:

• flake8-type-checking: TCH to TC

Stabilization

The following rules have been stabilized and are no longer in preview:

• builtin-import-shadowing (A004)
• mutable-contextvar-default (B039)
• fast-api-redundant-response-model (FAST001)
• fast-api-non-annotated-dependency (FAST002)
• dict-index-missing-items (PLC0206)
• pep484-style-positional-only-parameter (PYI063)
• redundant-final-literal (PYI064)
• bad-version-info-order (PYI066)
• parenthesize-chained-operators (RUF021)
• unsorted-dunder-all (RUF022)
• unsorted-dunder-slots (RUF023)
• assert-with-print-message (RUF030)
• unnecessary-default-type-args (UP043)

The following behaviors have been stabilized:

• ambiguous-variable-name (E741): Violations in stub files are now ignored. Stub authors typically don't control variable names.
• printf-string-formatting (UP031): Report all printf-like usages even if no autofix is available

The following fixes have been stabilized:

• zip-instead-of-pairwise (RUF007)

Preview features

• [flake8-datetimez] Exempt min.time() and max.time() (DTZ901) (#14394)
• [flake8-pie] Mark fix as unsafe if the following statement is a string literal (PIE790) (#14393)
• [flake8-pyi] New rule redundant-none-literal (PYI061) (#14316)
• [flake8-pyi] Add autofix for redundant-numeric-union (PYI041) (#14273)
• [ruff] New rule map-int-version-parsing (RUF048) (#14373)
• [ruff] New rule redundant-bool-literal (RUF038) (#14319)
• [ruff] New rule unraw-re-pattern (RUF039) (#14446)
• [pycodestyle] Exempt pytest.importorskip() calls (E402) (#14474)
• [pylint] Autofix suggests using sets when possible (PLR1714) (#14372)

Rule changes

• invalid-pyproject-toml (RUF200): Updated to reflect the provisionally accepted PEP 639.
• [flake8-pyi] Avoid panic in unfixable case (PYI041) (#14402)
• [flake8-type-checking] Correctly handle quotes in subscript expression when generating an autofix (#14371)
• [pylint] Suggest correct autofix for __contains__ (PLC2801) (#14424)

Configuration

• Ruff now emits a warning instead of an error when a configuration ignores a rule that has been removed (#14435)
• Ruff now validates that lint.flake8-import-conventions.aliases only uses valid module names and aliases (#14477)