Support decorators calling storyFn more than once

examples/official-storybook/stories/addon-knobs/with-knobs-decorators.stories.js

@@ -0,0 +1,18 @@
+import { withKnobs, text } from '@storybook/addon-knobs';
+
+export default {
+  title: 'Addons|Knobs.with decorators',
+};
+
+export const withDecoratorCallingStoryFunctionMoreThanOnce = () => {
+  return text('Text', 'Hello');
+};
+withDecoratorCallingStoryFunctionMoreThanOnce.story = {
+  decorators: [
+    withKnobs,
+    storyFn => {
+      storyFn();
+      return storyFn();
+    },
+  ],
+};

lib/addons/src/hooks.ts

@@ -143,6 +143,7 @@ const hookify = (fn: AbstractFunction) => (...args: any[]) => {
     hooks.currentPhase = 'MOUNT';
     hooks.currentHooks = [];
     hooks.hookListsMap.set(fn, hooks.currentHooks);
+    hooks.prevMountedDecorators.add(fn);
   }
   hooks.nextHookIndex = 0;
 
@@ -182,7 +183,6 @@ export const applyHooks = (
     while (hooks.hasUpdates) {
       hooks.hasUpdates = false;
       hooks.currentEffects = [];
-      hooks.prevMountedDecorators = hooks.mountedDecorators;
       result = decorated(context);
       numberOfRenders += 1;
       if (numberOfRenders > RENDER_LIMIT) {

lib/client-api/src/hooks.test.js

@@ -124,6 +124,18 @@ describe('Preview hooks', () => {
       run(() => {}, [decorator]);
       expect(effect).toHaveBeenCalledTimes(1);
     });
+    it("doesn't retrigger the effect from if decorator calls story twice", () => {
+      const effect = jest.fn();
+      const story = () => {
+        useEffect(effect, []);
+      };
+      const decorator = storyFn => {
+        storyFn();
+        return storyFn();
+      };
+      run(story, [decorator]);
+      expect(effect).toHaveBeenCalledTimes(1);
+    });
     it('retriggers the effect if some of the deps are changed', () => {
       const effect = jest.fn();
       let counter = 0;