1 files changed, 58 insertions, 0 deletions
diff --git a/node_modules/merge-source-map/index.js b/node_modules/merge-source-map/index.js
new file mode 100644
index 000000000..d15871c1d
--- /dev/null
+++ b/node_modules/merge-source-map/index.js
@@ -0,0 +1,58 @@
+var sourceMap = require('source-map'),
+    SourceMapConsumer = sourceMap.SourceMapConsumer,
+    SourceMapGenerator = sourceMap.SourceMapGenerator
+
+module.exports = merge
+
+/**
+ * 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.
+ *
+ * @param {object|undefined} oldMap old source map object
+ * @param {object|undefined} newmap new source map object
+ * @return {object|undefined} merged source map object, or undefined when both old and new source map are undefined
+ */
+function merge(oldMap, newMap) {
+
+  if (!oldMap)
+    return newMap
+  if (!newMap)
+    return oldMap
+
+  var oldMapConsumer = new SourceMapConsumer(oldMap),
+      newMapConsumer = new SourceMapConsumer(newMap),
+      mergedMapGenerator = new SourceMapGenerator()
+
+  // iterate on new map and overwrite original position of new map with one of old map
+  newMapConsumer.eachMapping(function(m) {
+
+    // pass when `originalLine` is null.
+    // It occurs in case that the node does not have origin in original code.
+    if (m.originalLine == null)
+      return
+
+    var origPosInOldMap = oldMapConsumer.originalPositionFor({line: m.originalLine, column: m.originalColumn})
+    if (origPosInOldMap.source == null)
+      return
+
+    mergedMapGenerator.addMapping({
+      original: {
+        line: origPosInOldMap.line,
+        column: origPosInOldMap.column
+      },
+      generated: {
+        line: m.generatedLine,
+        column: m.generatedColumn
+      },
+      source: m.source,
+      name: m.name
+    })
+  })
+
+  var mergedMap = JSON.parse(mergedMapGenerator.toString())
+  mergedMap.sources = oldMap.sources
+  mergedMap.sourcesContent = oldMap.sourcesContent
+  mergedMap.sourceRoot = oldMap.sourceRoot
+
+  return mergedMap
+}