merge-source-map

Merge old source map and new source map in multi-transform flow

API

1var merge = require('merge-source-map')

merge(oldMap, newMap)

Merge old source map and new source map and return merged. If old or new source map value is falsy, return another one as it is.

oldMap : object|undefined

old source map object

newmap : object|undefined

new source map object

Example

1var esprima    = require('esprima'),
2    estraverse = require('estraverse'),
3    escodegen  = require('escodegen'),
4    convert    = require('convert-source-map'),
5    merge      = require('merge-source-map')
6
7const CODE = 'a = 1',
8      FILEPATH = 'a.js'
9
10// create AST of original code
11var ast = esprima.parse(CODE, {sourceType: 'module', loc: true})
12
13// transform AST of original code
14estraverse.replace(ast, {
15  enter: function(node, parent) { /* change AST */ },
16  leave: function(node, parent) { /* change AST */ }
17})
18
19// generate code and source map from transformed AST
20var gen = escodegen.generate(ast, {
21  sourceMap: FILEPATH,
22  sourceMapWithCode: true,
23  sourceContent: CODE
24})
25
26// merge old source map and new source map
27var oldMap = convert.fromSource(CODE) && convert.fromSource(CODE).toObject(),
28    newMap = JSON.parse(gen.map.toString()),
29    mergedMap = merge(oldMap, newMap),
30    mapComment = convert.fromObject(mergedMap).toComment()
31
32// attach merge source map to transformed code
33var transformed = gen.code + '\n' + mapComment
34
35console.log(transformed);

Test

% npm install
% npm test

License

MIT (c) keik