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129 lines
4.8 KiB
129 lines
4.8 KiB
3 years ago
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# @jridgewell/gen-mapping
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> Generate source maps
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`gen-mapping` allows you to generate a source map during transpilation or minification.
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With a source map, you're able to trace the original location in the source file, either in Chrome's
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DevTools or using a library like [`@jridgewell/trace-mapping`][trace-mapping].
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You may already be familiar with the [`source-map`][source-map] package's `SourceMapGenerator`. This
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provides the same `addMapping` and `setSourceContent` API.
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## Installation
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```sh
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npm install @jridgewell/gen-mapping
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```
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## Usage
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```typescript
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import { GenMapping, addMapping, setSourceContent, encodedMap } from '@jridgewell/gen-mapping';
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const map = new GenMapping({
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file: 'output.js',
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sourceRoot: 'https://example.com/',
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});
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setSourceContent(map, 'input.js', `function foo() {}`);
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addMapping(map, {
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// Lines start at line 1, columns at column 0.
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generated: { line: 1, column: 0 },
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source: 'input.js',
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original: { line: 1, column: 0 },
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});
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addMapping(map, {
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generated: { line: 1, column: 9 },
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source: 'input.js',
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original: { line: 1, column: 9 },
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name: 'foo',
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});
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assert.deepEqual(encodedMap(map), {
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version: 3,
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file: 'output.js',
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names: ['foo'],
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sourceRoot: 'https://example.com/',
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sources: ['input.js'],
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sourcesContent: ['function foo() {}'],
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mappings: 'AAAA,SAASA',
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});
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```
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## Benchmarks
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```
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node v18.0.0
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amp.js.map
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gen-mapping: addSegment x 462 ops/sec ±1.53% (91 runs sampled)
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gen-mapping: addMapping x 471 ops/sec ±0.77% (93 runs sampled)
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source-map-js: addMapping x 178 ops/sec ±1.14% (84 runs sampled)
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source-map-0.6.1: addMapping x 178 ops/sec ±1.21% (84 runs sampled)
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source-map-0.8.0: addMapping x 177 ops/sec ±1.21% (83 runs sampled)
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Fastest is gen-mapping: addMapping,gen-mapping: addSegment
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gen-mapping: decoded output x 157,499,812 ops/sec ±0.25% (100 runs sampled)
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gen-mapping: encoded output x 625 ops/sec ±1.95% (88 runs sampled)
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source-map-js: encoded output x 162 ops/sec ±0.37% (84 runs sampled)
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source-map-0.6.1: encoded output x 161 ops/sec ±0.51% (84 runs sampled)
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source-map-0.8.0: encoded output x 191 ops/sec ±0.12% (90 runs sampled)
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Fastest is gen-mapping: decoded output
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***
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babel.min.js.map
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gen-mapping: addSegment x 35.38 ops/sec ±4.48% (48 runs sampled)
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gen-mapping: addMapping x 29.93 ops/sec ±5.03% (55 runs sampled)
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source-map-js: addMapping x 22.19 ops/sec ±3.39% (41 runs sampled)
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source-map-0.6.1: addMapping x 22.57 ops/sec ±2.90% (41 runs sampled)
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source-map-0.8.0: addMapping x 22.73 ops/sec ±2.84% (41 runs sampled)
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Fastest is gen-mapping: addSegment
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gen-mapping: decoded output x 157,767,591 ops/sec ±0.10% (99 runs sampled)
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gen-mapping: encoded output x 97.06 ops/sec ±1.69% (73 runs sampled)
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source-map-js: encoded output x 17.51 ops/sec ±2.27% (37 runs sampled)
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source-map-0.6.1: encoded output x 17.40 ops/sec ±4.61% (35 runs sampled)
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source-map-0.8.0: encoded output x 17.83 ops/sec ±4.85% (36 runs sampled)
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Fastest is gen-mapping: decoded output
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***
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preact.js.map
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gen-mapping: addSegment x 13,516 ops/sec ±0.27% (98 runs sampled)
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gen-mapping: addMapping x 12,117 ops/sec ±0.25% (97 runs sampled)
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source-map-js: addMapping x 4,285 ops/sec ±1.53% (98 runs sampled)
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source-map-0.6.1: addMapping x 4,482 ops/sec ±0.20% (100 runs sampled)
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source-map-0.8.0: addMapping x 4,482 ops/sec ±0.28% (99 runs sampled)
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Fastest is gen-mapping: addSegment
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gen-mapping: decoded output x 157,769,691 ops/sec ±0.06% (92 runs sampled)
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gen-mapping: encoded output x 18,610 ops/sec ±1.03% (93 runs sampled)
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source-map-js: encoded output x 5,397 ops/sec ±0.38% (97 runs sampled)
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source-map-0.6.1: encoded output x 5,422 ops/sec ±0.16% (100 runs sampled)
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source-map-0.8.0: encoded output x 5,595 ops/sec ±0.11% (100 runs sampled)
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Fastest is gen-mapping: decoded output
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***
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react.js.map
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gen-mapping: addSegment x 5,058 ops/sec ±0.27% (100 runs sampled)
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gen-mapping: addMapping x 4,352 ops/sec ±0.13% (97 runs sampled)
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source-map-js: addMapping x 1,569 ops/sec ±0.19% (99 runs sampled)
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source-map-0.6.1: addMapping x 1,550 ops/sec ±0.31% (97 runs sampled)
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source-map-0.8.0: addMapping x 1,560 ops/sec ±0.18% (99 runs sampled)
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Fastest is gen-mapping: addSegment
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gen-mapping: decoded output x 157,479,701 ops/sec ±0.14% (99 runs sampled)
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gen-mapping: encoded output x 6,392 ops/sec ±1.03% (94 runs sampled)
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source-map-js: encoded output x 2,213 ops/sec ±0.36% (99 runs sampled)
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source-map-0.6.1: encoded output x 2,238 ops/sec ±0.23% (100 runs sampled)
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source-map-0.8.0: encoded output x 2,304 ops/sec ±0.20% (100 runs sampled)
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Fastest is gen-mapping: decoded output
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```
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[source-map]: https://www.npmjs.com/package/source-map
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[trace-mapping]: https://github.com/jridgewell/trace-mapping
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