Merge pull request #670 from evgenykochetkov/warn-about-duplicate-sto…

…ry-name

Warn if story with a given name already exists

src/client/preview/__tests__/client_api.js

@@ -38,6 +38,10 @@ class StoryStore {
       return fn;
     }, null);
   }
+
+  hasStory(kind, name) {
+    return Boolean(this.getStory(kind, name));
+  }
 }
 
 describe('preview.client_api', () => {

src/client/preview/client_api.js

@@ -49,6 +49,10 @@ export default class ClientApi {
     });
 
     api.add = (storyName, getStory) => {
+      if (this._storyStore.hasStory(kind, storyName)) {
+        throw new Error(`Story of "${kind}" named "${storyName}" already exists`);
+      }
+
       // Wrap the getStory function with each decorator. The first
       // decorator will wrap the story function. The second will
       // wrap the first decorator and so on.