multi-stage-sourcemap 

This library provide re-mapping function for multi-level sourcemap.

Installation

`` sh
npm install multi-stage-sourcemap
`

Concept

$3

well-know basic sourcemap is no problem.

!basic-sourcemap.png

$3

Multi-level SourceMap has a problem.

Source Map Revision 3 Proposal doens't provide the way of mapping Minified Code to Original Code in the following figure.

!multiple-sourcemap.png

Example:

`
A.js -> B.js -> C.js
B.js.map -> C.js.map
`

We can't see from C.js to A.js.

$3

multi-stage-sourcemap can mapping C.js to A.js

!multiple-stage-sourcemap.png

> The easy but lossy way is to ignore the intermediate steps in the process for the purposes of debugging, the source location information from the translation is either ignored (the intermediate translation is considered the “Original Source”) or the source location information is carried through (the intermediate translation hidden). -- Source Map Revision 3 Proposal

multi-stage-sourcemap does that!

`
C.js -> ... -> A.js
`

Code:

` js
var transfer = require("multi-stage-sourcemap").transfer;
var cToAMap = transfer({fromSourceMap: cMap, toSourceMap: bMap});
`

Usage

$3

Return the re-mapped rawSourceMap string.

The only argument is an object with the following properties:

- fromSourceMap : Object - rawSourceMap or String - JSON.stringify(rawSourceMap)
- toSourceMap : Object - rawSourceMap or String - JSON.stringify(rawSourceMap)

rawSourceMap is like below object.

` js
var rawSourceMap = {
version: 3,
file: 'min.js',
names: ['bar', 'baz', 'n'],
sources: ['one.js', 'two.js'],
sourceRoot: 'http://exammuple.com/www/js/',
mappings: 'CAAC,IAAI,IAAM,SAAUA,GAClB,OAAOC,IAAID;CCDb,IAAI,IAAM,SAAUE,GAClB,OAAOA'
};
`

For details, please see mozilla/source-map.

Use Case

- [AltJS][] -> JavaScript -> minify
- [AltJS][] -> JavaScript -> [power-assert][]
- [power-assert][] supports multi-level sourcemaps using this module.
- twada/battlefield-sourcemaps
- power-assert 多段 SourceMap 対応の方針

etc...

AltJS is languages that compile to JS.
(It's contain ES6 with Traceur. )


[AltJS]: https://github.com/jashkenas/coffeescript/wiki/List-of-languages-that-compile-to-JS "List of languages that compile to JS · jashkenas/coffeescript Wiki"
[power-assert]: https://github.com/twada/power-assert "twada/power-assert"

Related library

- Rich-Harris/sorcery

Contributing

1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature`
5. Submit a pull request :D

License

MIT