From dd76272fb1e724227c941666d69acb158fe1c87a Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Tue, 3 Nov 2015 14:24:36 +0000
Subject: [PATCH] fix source map merging - closes #2522, fixes #2336

---
 packages/babel-cli/src/babel/file.js          |  2 +-
 .../src/transformation/file/index.js          | 31 ++++++++++++---
 packages/babel-core/test/api.js               | 39 +++++++++++++++++++
 3 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/packages/babel-cli/src/babel/file.js b/packages/babel-cli/src/babel/file.js
index b8e03b526f..068cd3b870 100644
--- a/packages/babel-cli/src/babel/file.js
+++ b/packages/babel-cli/src/babel/file.js
@@ -25,7 +25,7 @@ module.exports = function (commander, filenames, opts) {
     let offset = 0;
 
     _.each(results, function (result) {
-      let filename = result.filename;
+      let filename = result.filename || "stdout";
       code += result.code + "\n";
 
       if (result.map) {
diff --git a/packages/babel-core/src/transformation/file/index.js b/packages/babel-core/src/transformation/file/index.js
index 5d5e18f29f..9257f8f882 100644
--- a/packages/babel-core/src/transformation/file/index.js
+++ b/packages/babel-core/src/transformation/file/index.js
@@ -355,13 +355,32 @@ export default class File extends Store {
     if (inputMap) {
       let inputMapConsumer   = new sourceMap.SourceMapConsumer(inputMap);
       let outputMapConsumer  = new sourceMap.SourceMapConsumer(map);
-      let outputMapGenerator = sourceMap.SourceMapGenerator.fromSourceMap(outputMapConsumer);
-      outputMapGenerator.applySourceMap(inputMapConsumer);
 
-      let mergedMap = outputMapGenerator.toJSON();
-      mergedMap.sources = inputMap.sources;
-      mergedMap.file    = inputMap.file;
-      return mergedMap;
+      let mergedGenerator = new sourceMap.SourceMapGenerator({
+        file: inputMapConsumer.file,
+        sourceRoot: inputMapConsumer.sourceRoot
+      });
+
+      inputMapConsumer.eachMapping(function (mapping) {
+        mergedGenerator.addMapping({
+          source: inputMapConsumer.file,
+
+          original: {
+            line: mapping.originalLine,
+            column: mapping.originalColumn
+          },
+
+          generated: outputMapConsumer.generatedPositionFor({
+            line: mapping.generatedLine,
+            column: mapping.generatedColumn,
+            source: outputMapConsumer.file
+          })
+        });
+      });
+
+      let mergedMap = mergedGenerator.toJSON();
+      inputMap.mappings = mergedMap.mappings;
+      return inputMap;
     } else {
       return map;
     }
diff --git a/packages/babel-core/test/api.js b/packages/babel-core/test/api.js
index 445efb8921..e279d5f613 100644
--- a/packages/babel-core/test/api.js
+++ b/packages/babel-core/test/api.js
@@ -3,6 +3,7 @@ require("../lib/api/node");
 var buildExternalHelpers = require("../lib/tools/build-external-helpers");
 var transform            = require("../lib/api/node").transform;
 var Pipeline             = require("../lib/transformation/pipeline");
+var sourceMap            = require("source-map");
 var assert               = require("assert");
 var File                 = require("../lib/transformation/file").default;
 
@@ -33,6 +34,44 @@ suite("api", function () {
     });
   });
 
+  test("source map merging", function () {
+    var result = transform([
+      'function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }',
+      '',
+      'let Foo = function Foo() {',
+      '  _classCallCheck(this, Foo);',
+      '};',
+      '',
+      '//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInN0ZG91dCJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiOztJQUFNLEdBQUcsWUFBSCxHQUFHO3dCQUFILEdBQUciLCJmaWxlIjoidW5kZWZpbmVkIiwic291cmNlc0NvbnRlbnQiOlsiY2xhc3MgRm9vIHt9XG4iXX0='
+    ].join("\n"), {
+      sourceMap: true
+    });
+
+    assert.deepEqual([
+      "function _classCallCheck(instance, Constructor) {",
+      "  if (!(instance instanceof Constructor)) {",
+      '    throw new TypeError("Cannot call a class as a function");',
+      "  }",
+      "}",
+      "",
+      "let Foo = function Foo() {",
+      "  _classCallCheck(this, Foo);",
+      "};"
+    ].join("\n"), result.code);
+
+    var consumer = new sourceMap.SourceMapConsumer(result.map);
+
+    assert.deepEqual(consumer.originalPositionFor({
+      line: 7,
+      column: 4
+    }), {
+      name: null,
+      source: "stdout",
+      line: 1,
+      column: 6
+    });
+  });
+
   test("code option false", function () {
     return transformAsync("foo('bar');", { code: false }).then(function (result) {
       assert.ok(!result.code);