var sourceMap = require('source-map')
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var SourceMapConsumer = sourceMap.SourceMapConsumer
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var SourceMapGenerator = sourceMap.SourceMapGenerator
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module.exports = merge
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/**
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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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*
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* @param {object|string} [oldMap] old source map object
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* @param {object|string} [newmap] new source map object
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* @return {object|undefined} merged source map object, or undefined when both old and new source map are undefined
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*/
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function merge(oldMap, newMap) {
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if (!oldMap) return newMap
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if (!newMap) return oldMap
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var oldMapConsumer = new SourceMapConsumer(oldMap)
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var newMapConsumer = new SourceMapConsumer(newMap)
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var mergedMapGenerator = new SourceMapGenerator()
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// iterate on new map and overwrite original position of new map with one of old map
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newMapConsumer.eachMapping(function(m) {
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// pass when `originalLine` is null.
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// It occurs in case that the node does not have origin in original code.
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if (m.originalLine == null) return
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var origPosInOldMap = oldMapConsumer.originalPositionFor({
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line: m.originalLine,
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column: m.originalColumn
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})
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if (origPosInOldMap.source == null) return
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mergedMapGenerator.addMapping({
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original: {
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line: origPosInOldMap.line,
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column: origPosInOldMap.column
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},
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generated: {
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line: m.generatedLine,
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column: m.generatedColumn
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},
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source: origPosInOldMap.source,
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name: origPosInOldMap.name
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})
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})
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var consumers = [oldMapConsumer, newMapConsumer]
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consumers.forEach(function(consumer) {
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consumer.sources.forEach(function(sourceFile) {
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mergedMapGenerator._sources.add(sourceFile)
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var sourceContent = consumer.sourceContentFor(sourceFile)
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if (sourceContent != null) {
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mergedMapGenerator.setSourceContent(sourceFile, sourceContent)
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}
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})
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})
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mergedMapGenerator._sourceRoot = oldMap.sourceRoot
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mergedMapGenerator._file = oldMap.file
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return JSON.parse(mergedMapGenerator.toString())
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}
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