Is there any documentation around the Component Publishing Protocol?

[noahnu]

In https://storybook.js.org/docs/react/sharing/publish-storybook, it mentions the Component Publishing Protocol. I see Chromatic supports CPP level 1. If I didn't want to use Chromatic, is there an API spec for the CPP level 1 required APIs? I see "support for /metadata.json" but there's no docs on what "metadata.json" is

[itxch]

Its discussed here abit: #12202

But doesn't really seem well documented. I also couldn't actually get it working with chromatic which is annoying

[valentinpalkovic]

cc @kylegach, @jonniebigodes

[itxch]

@valentinpalkovic

Over the weekend I did actually try to "reverse engineer the spec" and I did managed to get it working where:

1. My platform creates a URL for each deployed version of storybook - and adds it to the versions object in the /metadata.json route, this file is the same across all deployed URLs.
2. Using version=x.y.z query parameter will take you to the right version (well actually in my case its version=Vx.y.z)
3. There is a base URL which will display the latest version.

But when I link to it from another Storybook, composition fails - it manages to get a list of stories, and looking in network tab it fetched /metadata.json and index.json successfully, as well as the iframe.html page. And in the drop down I see all the versions as per metadata.json. But when I select another version, I get JavaScript errors.

Again looking in the network tab its not actually calling the right URL, due to some regex issues in the Storybook code - happy to dive into here, or open a separate issue