@fuzdev/tsv_format_wasm

formatter for Svelte, TypeScript, and CSS

Rust-based formatter compiled to WASM. A near-Prettier formatter that tracks Prettier + prettier-plugin-svelte closely, with documented divergences.

Formatting only — for parser / AST extraction, see @fuzdev/tsv_parse_wasm, or @fuzdev/tsv_wasm for both plus a CLI.

Source of truth, full docs, and conformance notes: github.com/fuzdev/tsv.

Install

npm i @fuzdev/tsv_format_wasm

Usage

Three formatting functions: format_svelte, format_typescript, format_css. Each takes a source string and returns the formatted string, throwing on a parse error.

Node.js, Bun, Deno

Zero config — WASM is initialized synchronously at import time:

import {format_css, format_svelte, format_typescript} from '@fuzdev/tsv_format_wasm';

const formatted = format_svelte('<script>\nconst   x=1\n</script>');

Browsers and bundlers

Call await init() once before formatting. Bundlers that understand new URL('./file.wasm', import.meta.url) (Vite, Webpack, Rollup) resolve the WASM asset automatically:

import {format_svelte, init} from '@fuzdev/tsv_format_wasm';

await init();
const formatted = format_svelte('<script>\nconst   x=1\n</script>');

init_sync({ module }) is also exported for Workers and custom loading.

tsv is non-configurable: settings are fixed at Prettier's defaults except printWidth: 100, useTabs: true, singleQuote: true, and trailingComma: 'none' — no options, like gofmt and Black.

File scoping (IgnoreStack)

For tooling that needs tsv's exact file scoping, this package also exports an IgnoreStack class — the same hierarchical, git-faithful matcher (per-directory .gitignore, .formatignore, and .prettierignore layers) the tsv CLI uses to decide which files it formats. Build it from a repo's ignore files (one layer per directory, anchored at that directory), then query per path; locating the files and walking directories is the caller's job.

import {IgnoreStack} from '@fuzdev/tsv_format_wasm';

const stack = new IgnoreStack();
stack.push_gitignore('', 'build/\n*.log\n'); // a .gitignore (anchor '' = root)
stack.push_tsv('', '!keep.log\n'); // a .formatignore, evaluated after the gitignores
stack.is_ignored('build/out.js', false); // → true
stack.is_ignored('keep.log', false); // → false (the tsv layer re-includes it)

Status

v0.1 — pre-release. API may change.

License

MIT