Merge pull request #3108 from cspotcode/feature/fix-T2864

source-maps: Fix T2864

packages/babel-core/src/transformation/file/index.js

@@ -359,7 +359,17 @@ export default class File extends Store {
         sourceRoot: inputMapConsumer.sourceRoot
       });
 
+      // This assumes the output map always has a single source, since Babel always compiles a single source file to a
+      // single output file.
+      const source = outputMapConsumer.sources[0];
+
       inputMapConsumer.eachMapping(function (mapping) {
+        const generatedPosition = outputMapConsumer.generatedPositionFor({
+          line: mapping.generatedLine,
+          column: mapping.generatedColumn,
+          source: source
+        });
+        if(generatedPosition.column != null) {
           mergedGenerator.addMapping({
             source: mapping.source,
 
@@ -368,12 +378,9 @@ export default class File extends Store {
               column: mapping.originalColumn
             },
 
-          generated: outputMapConsumer.generatedPositionFor({
+            generated: generatedPosition
-            line: mapping.generatedLine,
-            column: mapping.generatedColumn,
-            source: outputMapConsumer.file
-          })
           });
+        }
       });
 
       let mergedMap = mergedGenerator.toJSON();