You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
228 lines
7.3 KiB
228 lines
7.3 KiB
1 month ago
|
# @jridgewell/gen-mapping
|
||
|
|
|
||
|
|
> Generate source maps
|
||
|
|
|
||
|
|
`gen-mapping` allows you to generate a source map during transpilation or minification.
|
||
|
|
With a source map, you're able to trace the original location in the source file, either in Chrome's
|
||
|
|
DevTools or using a library like [`@jridgewell/trace-mapping`][trace-mapping].
|
||
|
|
|
||
|
|
You may already be familiar with the [`source-map`][source-map] package's `SourceMapGenerator`. This
|
||
|
|
provides the same `addMapping` and `setSourceContent` API.
|
||
|
|
|
||
|
|
## Installation
|
||
|
|
|
||
|
|
```sh
|
||
|
|
npm install @jridgewell/gen-mapping
|
||
|
|
```
|
||
|
|
|
||
|
|
## Usage
|
||
|
|
|
||
|
|
```typescript
|
||
|
|
import { GenMapping, addMapping, setSourceContent, toEncodedMap, toDecodedMap } from '@jridgewell/gen-mapping';
|
||
|
|
|
||
|
|
const map = new GenMapping({
|
||
|
|
file: 'output.js',
|
||
|
|
sourceRoot: 'https://example.com/',
|
||
|
|
});
|
||
|
|
|
||
|
|
setSourceContent(map, 'input.js', `function foo() {}`);
|
||
|
|
|
||
|
|
addMapping(map, {
|
||
|
|
// Lines start at line 1, columns at column 0.
|
||
|
|
generated: { line: 1, column: 0 },
|
||
|
|
source: 'input.js',
|
||
|
|
original: { line: 1, column: 0 },
|
||
|
|
});
|
||
|
|
|
||
|
|
addMapping(map, {
|
||
|
|
generated: { line: 1, column: 9 },
|
||
|
|
source: 'input.js',
|
||
|
|
original: { line: 1, column: 9 },
|
||
|
|
name: 'foo',
|
||
|
|
});
|
||
|
|
|
||
|
|
assert.deepEqual(toDecodedMap(map), {
|
||
|
|
version: 3,
|
||
|
|
file: 'output.js',
|
||
|
|
names: ['foo'],
|
||
|
|
sourceRoot: 'https://example.com/',
|
||
|
|
sources: ['input.js'],
|
||
|
|
sourcesContent: ['function foo() {}'],
|
||
|
|
mappings: [
|
||
|
|
[ [0, 0, 0, 0], [9, 0, 0, 9, 0] ]
|
||
|
|
],
|
||
|
|
});
|
||
|
|
|
||
|
|
assert.deepEqual(toEncodedMap(map), {
|
||
|
|
version: 3,
|
||
|
|
file: 'output.js',
|
||
|
|
names: ['foo'],
|
||
|
|
sourceRoot: 'https://example.com/',
|
||
|
|
sources: ['input.js'],
|
||
|
|
sourcesContent: ['function foo() {}'],
|
||
|
|
mappings: 'AAAA,SAASA',
|
||
|
|
});
|
||
|
|
```
|
||
|
|
|
||
|
|
### Smaller Sourcemaps
|
||
|
|
|
||
|
|
Not everything needs to be added to a sourcemap, and needless markings can cause signficantly
|
||
|
|
larger file sizes. `gen-mapping` exposes `maybeAddSegment`/`maybeAddMapping` APIs that will
|
||
|
|
intelligently determine if this marking adds useful information. If not, the marking will be
|
||
|
|
skipped.
|
||
|
|
|
||
|
|
```typescript
|
||
|
|
import { maybeAddMapping } from '@jridgewell/gen-mapping';
|
||
|
|
|
||
|
|
const map = new GenMapping();
|
||
|
|
|
||
|
|
// Adding a sourceless marking at the beginning of a line isn't useful.
|
||
|
|
maybeAddMapping(map, {
|
||
|
|
generated: { line: 1, column: 0 },
|
||
|
|
});
|
||
|
|
|
||
|
|
// Adding a new source marking is useful.
|
||
|
|
maybeAddMapping(map, {
|
||
|
|
generated: { line: 1, column: 0 },
|
||
|
|
source: 'input.js',
|
||
|
|
original: { line: 1, column: 0 },
|
||
|
|
});
|
||
|
|
|
||
|
|
// But adding another marking pointing to the exact same original location isn't, even if the
|
||
|
|
// generated column changed.
|
||
|
|
maybeAddMapping(map, {
|
||
|
|
generated: { line: 1, column: 9 },
|
||
|
|
source: 'input.js',
|
||
|
|
original: { line: 1, column: 0 },
|
||
|
|
});
|
||
|
|
|
||
|
|
assert.deepEqual(toEncodedMap(map), {
|
||
|
|
version: 3,
|
||
|
|
names: [],
|
||
|
|
sources: ['input.js'],
|
||
|
|
sourcesContent: [null],
|
||
|
|
mappings: 'AAAA',
|
||
|
|
});
|
||
|
|
```
|
||
|
|
|
||
|
|
## Benchmarks
|
||
|
|
|
||
|
|
```
|
||
|
|
node v18.0.0
|
||
|
|
|
||
|
|
amp.js.map
|
||
|
|
Memory Usage:
|
||
|
|
gen-mapping: addSegment 5852872 bytes
|
||
|
|
gen-mapping: addMapping 7716042 bytes
|
||
|
|
source-map-js 6143250 bytes
|
||
|
|
source-map-0.6.1 6124102 bytes
|
||
|
|
source-map-0.8.0 6121173 bytes
|
||
|
|
Smallest memory usage is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Adding speed:
|
||
|
|
gen-mapping: addSegment x 441 ops/sec ±2.07% (90 runs sampled)
|
||
|
|
gen-mapping: addMapping x 350 ops/sec ±2.40% (86 runs sampled)
|
||
|
|
source-map-js: addMapping x 169 ops/sec ±2.42% (80 runs sampled)
|
||
|
|
source-map-0.6.1: addMapping x 167 ops/sec ±2.56% (80 runs sampled)
|
||
|
|
source-map-0.8.0: addMapping x 168 ops/sec ±2.52% (80 runs sampled)
|
||
|
|
Fastest is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Generate speed:
|
||
|
|
gen-mapping: decoded output x 150,824,370 ops/sec ±0.07% (102 runs sampled)
|
||
|
|
gen-mapping: encoded output x 663 ops/sec ±0.22% (98 runs sampled)
|
||
|
|
source-map-js: encoded output x 197 ops/sec ±0.45% (84 runs sampled)
|
||
|
|
source-map-0.6.1: encoded output x 198 ops/sec ±0.33% (85 runs sampled)
|
||
|
|
source-map-0.8.0: encoded output x 197 ops/sec ±0.06% (93 runs sampled)
|
||
|
|
Fastest is gen-mapping: decoded output
|
||
|
|
|
||
|
|
|
||
|
|
***
|
||
|
|
|
||
|
|
|
||
|
|
babel.min.js.map
|
||
|
|
Memory Usage:
|
||
|
|
gen-mapping: addSegment 37578063 bytes
|
||
|
|
gen-mapping: addMapping 37212897 bytes
|
||
|
|
source-map-js 47638527 bytes
|
||
|
|
source-map-0.6.1 47690503 bytes
|
||
|
|
source-map-0.8.0 47470188 bytes
|
||
|
|
Smallest memory usage is gen-mapping: addMapping
|
||
|
|
|
||
|
|
Adding speed:
|
||
|
|
gen-mapping: addSegment x 31.05 ops/sec ±8.31% (43 runs sampled)
|
||
|
|
gen-mapping: addMapping x 29.83 ops/sec ±7.36% (51 runs sampled)
|
||
|
|
source-map-js: addMapping x 20.73 ops/sec ±6.22% (38 runs sampled)
|
||
|
|
source-map-0.6.1: addMapping x 20.03 ops/sec ±10.51% (38 runs sampled)
|
||
|
|
source-map-0.8.0: addMapping x 19.30 ops/sec ±8.27% (37 runs sampled)
|
||
|
|
Fastest is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Generate speed:
|
||
|
|
gen-mapping: decoded output x 381,379,234 ops/sec ±0.29% (96 runs sampled)
|
||
|
|
gen-mapping: encoded output x 95.15 ops/sec ±2.98% (72 runs sampled)
|
||
|
|
source-map-js: encoded output x 15.20 ops/sec ±7.41% (33 runs sampled)
|
||
|
|
source-map-0.6.1: encoded output x 16.36 ops/sec ±10.46% (31 runs sampled)
|
||
|
|
source-map-0.8.0: encoded output x 16.06 ops/sec ±6.45% (31 runs sampled)
|
||
|
|
Fastest is gen-mapping: decoded output
|
||
|
|
|
||
|
|
|
||
|
|
***
|
||
|
|
|
||
|
|
|
||
|
|
preact.js.map
|
||
|
|
Memory Usage:
|
||
|
|
gen-mapping: addSegment 416247 bytes
|
||
|
|
gen-mapping: addMapping 419824 bytes
|
||
|
|
source-map-js 1024619 bytes
|
||
|
|
source-map-0.6.1 1146004 bytes
|
||
|
|
source-map-0.8.0 1113250 bytes
|
||
|
|
Smallest memory usage is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Adding speed:
|
||
|
|
gen-mapping: addSegment x 13,755 ops/sec ±0.15% (98 runs sampled)
|
||
|
|
gen-mapping: addMapping x 13,013 ops/sec ±0.11% (101 runs sampled)
|
||
|
|
source-map-js: addMapping x 4,564 ops/sec ±0.21% (98 runs sampled)
|
||
|
|
source-map-0.6.1: addMapping x 4,562 ops/sec ±0.11% (99 runs sampled)
|
||
|
|
source-map-0.8.0: addMapping x 4,593 ops/sec ±0.11% (100 runs sampled)
|
||
|
|
Fastest is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Generate speed:
|
||
|
|
gen-mapping: decoded output x 379,864,020 ops/sec ±0.23% (93 runs sampled)
|
||
|
|
gen-mapping: encoded output x 14,368 ops/sec ±4.07% (82 runs sampled)
|
||
|
|
source-map-js: encoded output x 5,261 ops/sec ±0.21% (99 runs sampled)
|
||
|
|
source-map-0.6.1: encoded output x 5,124 ops/sec ±0.58% (99 runs sampled)
|
||
|
|
source-map-0.8.0: encoded output x 5,434 ops/sec ±0.33% (96 runs sampled)
|
||
|
|
Fastest is gen-mapping: decoded output
|
||
|
|
|
||
|
|
|
||
|
|
***
|
||
|
|
|
||
|
|
|
||
|
|
react.js.map
|
||
|
|
Memory Usage:
|
||
|
|
gen-mapping: addSegment 975096 bytes
|
||
|
|
gen-mapping: addMapping 1102981 bytes
|
||
|
|
source-map-js 2918836 bytes
|
||
|
|
source-map-0.6.1 2885435 bytes
|
||
|
|
source-map-0.8.0 2874336 bytes
|
||
|
|
Smallest memory usage is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Adding speed:
|
||
|
|
gen-mapping: addSegment x 4,772 ops/sec ±0.15% (100 runs sampled)
|
||
|
|
gen-mapping: addMapping x 4,456 ops/sec ±0.13% (97 runs sampled)
|
||
|
|
source-map-js: addMapping x 1,618 ops/sec ±0.24% (97 runs sampled)
|
||
|
|
source-map-0.6.1: addMapping x 1,622 ops/sec ±0.12% (99 runs sampled)
|
||
|
|
source-map-0.8.0: addMapping x 1,631 ops/sec ±0.12% (100 runs sampled)
|
||
|
|
Fastest is gen-mapping: addSegment
|
||
|
|
|
||
|
|
Generate speed:
|
||
|
|
gen-mapping: decoded output x 379,107,695 ops/sec ±0.07% (99 runs sampled)
|
||
|
|
gen-mapping: encoded output x 5,421 ops/sec ±1.60% (89 runs sampled)
|
||
|
|
source-map-js: encoded output x 2,113 ops/sec ±1.81% (98 runs sampled)
|
||
|
|
source-map-0.6.1: encoded output x 2,126 ops/sec ±0.10% (100 runs sampled)
|
||
|
|
source-map-0.8.0: encoded output x 2,176 ops/sec ±0.39% (98 runs sampled)
|
||
|
|
Fastest is gen-mapping: decoded output
|
||
|
|
```
|
||
|
|
|
||
|
|
[source-map]: https://www.npmjs.com/package/source-map
|
||
|
|
[trace-mapping]: https://github.com/jridgewell/trace-mapping
|