92 lines
2.2 KiB
Markdown
92 lines
2.2 KiB
Markdown
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# merge-source-map
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[](https://npmjs.org/package/merge-source-map)
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[](https://npmjs.org/package/merge-source-map)
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[](https://travis-ci.org/keik/merge-source-map)
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[](https://coveralls.io/github/keik/merge-source-map)
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Merge old source map and new source map in multi-transform flow
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# API
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```javascript
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var merge = require('merge-source-map')
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```
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## `merge(oldMap, newMap)`
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Merge old source map and new source map and return merged.
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If old or new source map value is falsy, return another one as it is.
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<dl>
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<dt>
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<code>oldMap</code> : <code>object|undefined</code>
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</dt>
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<dd>
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old source map object
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</dd>
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<dt>
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<code>newmap</code> : <code>object|undefined</code>
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</dt>
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<dd>
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new source map object
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</dd>
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</dl>
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# Example
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```javascript
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var esprima = require('esprima'),
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estraverse = require('estraverse'),
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escodegen = require('escodegen'),
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convert = require('convert-source-map'),
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merge = require('merge-source-map')
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const CODE = 'a = 1',
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FILEPATH = 'a.js'
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// create AST of original code
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var ast = esprima.parse(CODE, {sourceType: 'module', loc: true})
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// transform AST of original code
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estraverse.replace(ast, {
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enter: function(node, parent) { /* change AST */ },
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leave: function(node, parent) { /* change AST */ }
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})
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// generate code and source map from transformed AST
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var gen = escodegen.generate(ast, {
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sourceMap: FILEPATH,
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sourceMapWithCode: true,
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sourceContent: CODE
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})
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// merge old source map and new source map
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var oldMap = convert.fromSource(CODE) && convert.fromSource(CODE).toObject(),
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newMap = JSON.parse(gen.map.toString()),
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mergedMap = merge(oldMap, newMap),
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mapComment = convert.fromObject(mergedMap).toComment()
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// attach merge source map to transformed code
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var transformed = gen.code + '\n' + mapComment
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console.log(transformed);
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```
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# Test
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```
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% npm install
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% npm test
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```
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# License
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MIT (c) keik
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