Add --sourcemap-sources-root to RN packager

Reviewed By: davidaurelio

Differential Revision: D4357122

fbshipit-source-id: dc19474aa54ea4684a6b1c586a9d1e5da0980327

react-packager/src/lib/relativizeSourceMap.js

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ */
+
+'use strict';
+
+const path = require('path');
+
+import type { MixedSourceMap } from './SourceMap';
+
+function relativizeSourceMapInternal(sourceMap: any, sourcesRoot: string) {
+  if (sourceMap.sections) {
+    for (var i = 0; i < sourceMap.sections.length; i++) {
+      relativizeSourceMapInternal(sourceMap.sections[i].map, sourcesRoot);
+    }
+  } else {
+    for (var i = 0; i < sourceMap.sources.length; i++) {
+      sourceMap.sources[i] = path.relative(sourcesRoot, sourceMap.sources[i]);
+    }
+  }
+}
+
+function relativizeSourceMap(sourceMap: MixedSourceMap, sourcesRoot?: string): MixedSourceMap {
+  if (!sourcesRoot) {
+    return sourceMap;
+  }
+  relativizeSourceMapInternal(sourceMap, sourcesRoot);
+  return sourceMap;
+}
+
+module.exports = relativizeSourceMap;