merge-source-map

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

# API

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

## <tt>merge(oldMap, newMap)</tt>

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

var esprima = require('esprima'),
estraverse = require('estraverse'),
escodegen = require('escodegen'),
convert = require('convert-source-map'),
merge = require('merge-source-map')
const CODE = 'a = 1',
FILEPATH = 'a.js'
// create AST of original code
var ast = esprima.parse(CODE, {sourceType: 'module', loc: true})
// transform AST of original code
estraverse.replace(ast, {
enter: function(node, parent) { /* change AST */ },
leave: function(node, parent) { /* change AST */ }
})
// generate code and source map from transformed AST
var gen = escodegen.generate(ast, {
sourceMap: FILEPATH,
sourceMapWithCode: true,
sourceContent: CODE
})
// merge old source map and new source map
var oldMap = convert.fromSource(CODE) && convert.fromSource(CODE).toObject(),
newMap = JSON.parse(gen.map.toString()),
mergedMap = merge(oldMap, newMap),
mapComment = convert.fromObject(mergedMap).toComment()
// attach merge source map to transformed code
var transformed = gen.code + '\n' + mapComment
console.log(transformed);

# Test

% npm install
% npm test

# License

MIT (c) keik