Fix/error handling

[ndelangen]

Issue: #10577 #10664

when there's an error in one of the stories initially, the preview & sidebar will go in a perpetual loading-state & error doesn't show up in the preview

What I did

• made sure that if an error occurs storybook preview renders an error.
• Re-use the UI from refs to display the error in sidebar
• Add the error that occurred to setStories event

[ndelangen]

This is what an error now looks like when loading stories fails:

This is what it looks like when a story-file is loaded successfully, but the story throws an error being rendered:

[yannbf]

magic number?

[tmeasday]

I'm OK with the idea of including errors in SetStoriesPayload (if we need to know about it on the manager side).

But I don't like the changed event behaviour. Let's avoid incremental changes to events like this, that's how we ended up with the complex mess of incoherent events we had before.

Let's be careful about what events are emitted when and document things. I tried to do that already although it could be more comphrehensive I think: https://github.com/storybookjs/storybook/blob/a9fc57fe490e5befcb4bdd4f77f6897d283d8263/lib/core/README.md#events-on-startup

[yannbf]

I don't have 100% context so can't help that much in code, but I ran the official storybook in a few scenarios:
1 - with a wrong glob in main.js:

stories: ['../../lib/ui/src/**/Wrong.stories.(js|tsx|mdx)']

2 - with a correct glob but everything commented out in the story:

stories: ['../../lib/ui/src/**/Sidebar.stories.(js|tsx|mdx)']

3 - with a correct glob, exporting a single story but not default exporting anything

Scenarios 1, 2 and 3 leave me in this screen:

4 - with a correct glob + the file only has a throw new Error('error!!!');
5 - with a correct glob + the file has a story that throws an error

Scenarios 4 and 5 work as you mentioned in the PR.

And a small observation, that you can ignore if you want, the component /components/sidebar/RefBlocks -> ErrorBlock has the following text:

Ow now! something went wrong loading this storybook

Shouldn't it be

Oh no! Something went wrong loading this storybook.

[ndelangen]

I'll investigate the scenarios:

• all stories load fine, but they don't export/define any stories
  should show a message in the sidebar
• story-files are missing (glob matches nothing)
  should show a warning in terminal?

[ndelangen]

Here's what happens if a ref/frame results in a successful SET_STORIES, but the contents are empty:

[tmeasday]

Maybe we can make a better UI for the no stories case? WDYT?

[ndelangen]

new UI

[tmeasday]

Looking good @ndelangen. I was actually thinking something similar in the preview pane. Wdyt?

[tmeasday]

@domyen want to weigh in?