@srcmap/gen-mapping

Drop-in replacement for @jridgewell/gen-mapping powered by Rust via WebAssembly.

Same API, same types, same behavior. Swap the import and get source map generation backed by Rust under the hood.

Install

npm install @srcmap/gen-mapping

Usage

// Before:
// import { GenMapping, addMapping, toEncodedMap } from '@jridgewell/gen-mapping'

// After:
import { GenMapping, addMapping, toEncodedMap } from '@srcmap/gen-mapping'

const map = new GenMapping({ file: 'bundle.js' })

addMapping(map, {
  generated: { line: 1, column: 0 },
  source: 'src/app.ts',
  original: { line: 10, column: 4 },
  name: 'handleClick',
  content: 'const handleClick = () => { ... }',
})

const encoded = toEncodedMap(map)

// Cleanup WASM memory (optional, also via `using` with Symbol.dispose)
map.free()

API compatibility

All exports from @jridgewell/gen-mapping are supported:

| Export | Description | |--------|-------------| | GenMapping | Main class — creates a new source map builder | | addMapping(map, mapping) | Add a mapping (1-based lines, 0-based columns) | | maybeAddMapping(map, mapping) | Add only if it differs from the previous mapping on the same line | | setSourceContent(map, source, content) | Set source content for a source file | | setIgnore(map, source, ignore?) | Mark a source as ignored | | toEncodedMap(map) | Return as encoded source map (VLQ string mappings) | | toDecodedMap(map) | Return as decoded source map (array mappings) | | allMappings(map) | Return all mappings as Mapping[] | | fromMap(input) | Construct from an existing source map |

Line/column convention

Follows @jridgewell/gen-mapping conventions:

• addMapping / maybeAddMapping: 1-based lines, 0-based columns
• Decoded mappings output: 0-based lines, 0-based columns

Differences from @jridgewell/gen-mapping

• WASM memory: Call map.free() when done, or use using map = new GenMapping(...) with Symbol.dispose
• VLQ encoding runs in WASM: No JS-side encoding overhead

Part of srcmap

High-performance source map tooling written in Rust. See also:

• @srcmap/trace-mapping - Drop-in for @jridgewell/trace-mapping (consumer)
• @srcmap/remapping - Drop-in for @ampproject/remapping (composition)
• @srcmap/generator-wasm - Lower-level WASM generator API

License

MIT