[Storybook 6.4] argTypeTargetsV7 breaks on stories without args

[yannbf]

Describe the bug

To Reproduce
1 - Go to react-ts

2 - Enable argTypeTargetsV7:

  features: {
    argTypeTargetsV7: true,
  },

3 - Run react-ts storybook

3 - Go to http://localhost:9011/?path=/story/examples-emoji-button--basic

4 - Get the error. This is the story that causes the error:

export const Basic = () => <EmojiButton label="Click me" />;

It actually happens with any story that does not define args or argTypes, be it CSF1 2 or 3.

Things should break because context.args is undefined here:
https://github.com/storybookjs/storybook/blob/next/lib/store/src/prepareStory.ts#L169

[tmeasday]

🤔 hmm, why would context.args be undefined? I think it should always be defined... Will see if I can repro @yannbf

[tmeasday]

@yannbf is there something different you are doing here? I am not seeing it:

export const CSF1 = (args, context) => console.log(args, context) || <div>Hello</div>

[yannbf]

Hey @tmeasday I've got a simple way to reproduce it in the monorepo, I updated the steps in the issue description. Hope it helps!

[tmeasday]

Ahh, got it, the component I was testing had some auto-generated argTypes 🤦

[shilman]

Jiminy cricket!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.4.0-rc.10 containing PR #16790 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb upgrade --prerelease

Closing this issue. Please re-open if you think there's still more to do.