Fix the plugin return object for keep-enabled gzipping

index.js

@@ -59,9 +59,9 @@ module.exports = {
             if (keep) {
               self.log('keep is enabled, added gzipped files to `context.distFiles`', { verbose: true });
               return {
-                distFiles: gzippedFiles,
+                distFiles: [].concat(gzippedFiles), // needs to be a copy
                 gzippedFiles: gzippedFiles
-              }
+              };
             }
             return { gzippedFiles: gzippedFiles };
           })

tests/unit/index-nodetest.js

@@ -184,6 +184,16 @@ describe('gzip plugin', function() {
             done(reason);
           });
       });
+
+      it('does not use the same object for gzippedFiles and distFiles', function(done) {
+        return assert.isFulfilled(plugin.willUpload(context))
+          .then(function(result) {
+            assert.notStrictEqual(result.distFiles, result.gzippedFiles);
+            done();
+          }).catch(function(reason){
+            done(reason);
+          });
+      });
     });
   });
 });