@rsvelte/lint

A fast, native Svelte linter built directly on the rsvelte compiler — no second ESTree parse, no Node.js in the hot path. rsvelte-lint combines two diagnostic sources in one pass:

1. Validator wrap — the rsvelte compiler already emits ~70 warning codes, ~145 error codes, and 42 a11y_* rules during analysis. Those surface directly as lint diagnostics.
2. Native rule engine — a single shared AST walk that ports eslint-plugin-svelte's rules natively (all 80 upstream rules are ported and validated byte-for-byte against the plugin's own fixtures — see Rule coverage).

⚠️ Early stage (v0). Output and flags are stabilising.

Install

npm install -D @rsvelte/lint
# pnpm add -D @rsvelte/lint
# yarn add -D @rsvelte/lint

The package resolves the right prebuilt native binary for your platform via optionalDependencies — there's no oxfmt-style external dependency to install alongside it; rsvelte-lint is self-contained. Supported targets:

| OS | Architecture | |---|---| | macOS | arm64, x64 | | Linux | x64 (glibc), arm64 (glibc) | | Windows | x64 (MSVC) |

If your platform isn't listed, please open an issue.

How the CLI is launched

rsvelte-lint's bin entry is a small Node launcher that resolves the platform-native binary from optionalDependencies and execs it, forwarding argv/stdio and the exit code — one Node cold start per invocation. There is no install-time step and nothing to allow in a package manager's build-script gate (e.g. pnpm's onlyBuiltDependencies).

Usage

npx rsvelte-lint src/                 # lint a directory (recurses, finds *.svelte)
npx rsvelte-lint src/App.svelte       # lint a single file
npx rsvelte-lint --fix src/           # apply autofixes in place
npx rsvelte-lint --format sarif src/  # SARIF for CI code-scanning
npx rsvelte-lint --list-rules         # print every native rule + default severity

Add it to your package.json:

{
  "scripts": {
    "lint": "rsvelte-lint src/",
    "lint:fix": "rsvelte-lint --fix src/"
  }
}

Directory arguments are walked recursively for .svelte files (skipping nothing special — point it at src/, not the whole repo, if you have generated .svelte output you don't want linted, or use ignores in your config — see Configuration). Multiple paths and files can be mixed on one invocation: rsvelte-lint src/lib src/routes/+page.svelte.

Other flags:

| Flag | Effect | |---|---| | --off <rule> | Turn a rule off (repeatable) | | --error <rule> | Treat a rule as an error (repeatable) | | --max-warnings <n> | Exit non-zero if warnings exceed n | | --config <file> | Explicit config path (see Configuration) |

Run rsvelte-lint --help for the authoritative list.

Configuration

rsvelte-lint looks for rsvelte-lint.json (or .rsvelte-lintrc.json), walking upward from the working directory, unless --config <file> is passed explicitly:

{
  "extends": ["recommended"],
  "rules": {
    "svelte/no-at-html-tags": "error",
    "svelte/button-has-type": ["warn", { "submit": true, "reset": false }],
    "svelte/no-restricted-html-elements": ["error", { "elements": ["marquee"] }]
  },
  "files": ["src/**/*.svelte"],
  "ignores": ["**/generated/**"]
}

• extends — ["recommended"] (the default even with no config file at all) runs every rule at its declared default severity. ["none"] (aliases: "off", "empty") starts from a baseline where nothing runs unless explicitly turned on in rules.
• rules — keyed by rule id (a native svelte/* id, or a bare compiler code like a11y_img_redundant_alt for validator-wrapped findings). A value is either a severity scalar — "off" / "warn" / "error", or the numeric ESLint equivalents 0 / 1 / 2 — or a [severity, options] pair, where options is passed straight through to the rule (most rules read options[0] as an object, matching ESLint's variadic rule-options convention).
• files / ignores — gitignore-flavoured globs (**, *, ?) over the path relative to the working directory. An empty files list matches every candidate passed on the command line; ignores always wins over files.

Run --list-rules to see every native rule's id, category, default severity, and whether it's autofixable; rules with an options schema are marked (options).

The same file drives editor diagnostics: @rsvelte/language-server and the rsvelte VS Code extension discover it by walking up from the file being linted, so the editor and CI agree on the rule set. files / ignores stay CLI-only — an editor lints the document it is handed.

Migrating from ESLint

rsvelte-lint ships as a complement to eslint-plugin-svelte first, not (yet) a replacement — the two are designed to run side by side without double-reporting:

# Import your existing eslint.config.js svelte/* severities into rsvelte-lint
npx rsvelte-lint --config-from-eslint eslint.config.js src/

# Generate a flat-config snippet that turns the native-owned svelte/* rules
# off in ESLint, so each finding fires exactly once
npx rsvelte-lint --print-eslint-config > eslint.rsvelte.json

--config-from-eslint <file> statically parses an ESLint flat config and imports its svelte/* rule severities as overrides on top of your rsvelte-lint.json (or the recommended preset if you have none). --print-eslint-config prints a flat-config object disabling every rsvelte-lint-owned rule id in ESLint; spread it into your eslint.config.js.

Suppressing findings

Three suppression forms are supported, so existing ESLint-annotated code and Svelte's own convention both work with no changes:

• <!-- eslint-disable-next-line svelte/no-at-html-tags --> / <!-- eslint-disable-line [rule ...] --> — suppress specific rules (or every rule, with no ids) on the following/same line.
• <!-- eslint-disable [rule ...] --> … <!-- eslint-enable [rule ...] --> — suppress a block range; an unmatched eslint-disable runs to end of file.
• <!-- svelte-ignore <code> --> — Svelte's own convention, treated like disable-next-line for the listed compiler/rule codes. Unlike eslint-disable, a bare <!-- svelte-ignore --> with no codes suppresses nothing (it never wildcards).

A file can also carry an inline configure comment to override a rule's severity or options for that file only, matching ESLint's own inline-config syntax:

<script>
  /* eslint svelte/sort-attributes: ["error", { "order": ["id", "class"] }] */
</script>

This form is parsed leniently (single-quoted strings, unquoted keys, and trailing commas are all accepted, matching ESLint's own levn parser); an unparseable comment is ignored rather than treated as an error, so it never turns into a wrong finding.

Output formats and exit codes

--format accepts human (default), human-verbose, machine, machine-verbose, github-actions (alias github), or sarif. The human formats print a rsvelte-lint found N errors and M warnings in K files summary; the others stay line-oriented for tooling.

| Exit code | Meaning | |---|---| | 0 | No errors (and, if --max-warnings is set, warnings within budget) | | 1 | At least one error, or warnings exceeded --max-warnings | | 2 | Usage error (bad --format, unreadable config, no input paths) |

CI integration

# .github/workflows/lint.yml
- run: npx rsvelte-lint --format github-actions src/

--format github-actions emits ::error file=…::… / ::warning file=…::… workflow commands so findings show up as inline annotations on the PR diff. For code-scanning integration, use --format sarif with github/codeql-action/upload-sarif:

- run: npx rsvelte-lint --format sarif src/ > rsvelte-lint.sarif
  continue-on-error: true
- uses: github/codeql-action/upload-sarif@v3
  with:
    sarif_file: rsvelte-lint.sarif

Rule coverage

All 80 eslint-plugin-svelte rules are ported natively and validated byte-for-byte (message, line, column, autofix output, and editor suggestions) against that plugin's own upstream fixtures by a CI-enforced compat oracle. The authoritative list of ported rules and the handful of fixtures that genuinely need a JS/TS tokenizer or type checker (out of scope for the native engine, covered separately) is the oracle test registry at crates/rsvelte_lint/tests/eslint_plugin_oracle.rs. The default recommended preset runs every rule at its declared default severity: most correctness and style rules default to warn (a handful — e.g. no-dupe-else-if-blocks, no-dupe-style-properties, no-object-in-text-mustaches — to error), while all pure-formatting rules (owned by the sibling @rsvelte/fmt) plus a set of opinionated opt-in rules such as button-has-type, no-restricted-html-elements, and sort-attributes default to off and must be enabled via rules in your config. Run --list-rules to see the full default-severity table.

Supported platforms

See Install above.

See also

• @rsvelte/oxlint-plugin — the same diagnostics as an oxlint plugin, if you'd rather run one linter over JS/TS and Svelte together. Note the current limits of oxlint's .svelte support (script-less files, markup diagnostic positions) — this CLI is the faithful one.
• @rsvelte/fmt — the sibling Rust-powered formatter for .svelte + JS/TS/CSS.
• @rsvelte/svelte-check — type-checking CLI.
• @rsvelte/compiler — the compiler itself, as WebAssembly.
• crates/rsvelte_lint — the Rust crate this package wraps, including the architecture decision record and demo.

License

MIT