Storybook: Using raw HTML in MDX files strips classes

[fraincs]

Describe the bug
When using mdx as a source of doc, not wrapping the html in a story component strips all classes.

To Reproduce
Steps to reproduce the behavior:

1. Create a mdx file
2. Paste code from code snippet
3. No classes are applied to the DOM elements

Expected behavior
Using raw HTML in mdx would behave as straight HTML

Screenshots

Code snippets
```
import { Meta } from "@storybook/addon-docs/blocks";

500 #F47321

500 #FCB736

```

Note that nor class or ClassName are working

System:
System:
OS: macOS Mojave 10.14.6
CPU: (4) x64 Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
Binaries:
Node: 12.7.0 - ~/.nvm/versions/node/v12.7.0/bin/node
Yarn: 1.19.1 - ~/Repos/sg-orbit/node_modules/.bin/yarn
npm: 6.10.0 - ~/.nvm/versions/node/v12.7.0/bin/npm
Browsers:
Chrome: 77.0.3865.120
Firefox: 69.0.1
Safari: 13.0.2
npmPackages:
@storybook/addon-actions: 5.2.4 => 5.2.4
@storybook/addon-console: 1.2.1 => 1.2.1
@storybook/addon-docs: 5.2.4 => 5.2.4
@storybook/addon-knobs: 5.2.4 => 5.2.4

[shilman]

@fraincs This was introduced in https://github.com/storybookjs/storybook/pull/7771, which tries to isolate "document theming" vs. "user story theming", and is a little tricky.

• [ ] Right now AFAIK there is no way to distinguish between an h1 generated by markdown (e.g. # Heading) and a user-added h1 (e.g. <h1>Heading</h1>). We clearly want to style the former, and may or may not want to style the latter. Thoughts?
• [ ] If we could preserve the user's classes, and ADD classes that match the document styling, would that be sufficient?

[fraincs]

• [ ] Right now AFAIK there is no way to distinguish between an h1 generated by markdown (e.g. # Heading) and a user-added h1 (e.g. <h1>Heading</h1>). We clearly want to style the former, and may or may not want to style the latter. Thoughts?

Exactly, I currently documenting how H1s are affected by some atomic CSS classes, and wouldn't want Storybook styling to bleed. e.g.

• [ ] If we could preserve the user's classes, and ADD classes that match the document styling, would that be sufficient?

Yes as long as user's classes are applied after the classes that match the document styling

[vidarc]

Don't know if this will help, but with version 5.3.0-alpha.38, if I import a Component into my MDX file, that component's classes do not get stripped out, but also the storybook classes do not get added.

[ndelangen]

@fraincs could you open a PR with a reproduction perhaps? That would make it easier to start work.

[fraincs]

@ndelangen see https://github.com/storybookjs/storybook/pull/8897

[lostPixels]

I just encountered this issue when trying to add our company logo to the introduction of our styleguide. Not a huge problem, but it would be nice to be able to selective style elements in our MDX file with a CSS file.

[atanasster]

@fraincs & everyone else , I just tried the reproduction sample on the latest 5.3 beta and can not reproduce either issue:
The class names are not stripped and also the sb-docs classes are kept in there.

Can you guys please try to upgrade to the latest 5.3 beta and post here if you can still reproduce the issue?

[shilman]

Thanks @atanasster. Gonna close this!!! Please scream if it's still broken for you 😱

[patricklafrance]

@atanasster @shilman

It's not strip anymore, but CSS classes added by MDX have precedence over the custom classes added by the user.

You can see it in action in the following screenshot. Same code rendered twiced. The first box is in a story, the second is not.

It would be nice if we could import a block like <ResetStyles> and paste inside code that shouldn't be affected by default MDX styles.

What do you think?

[atanasster]

@patricklafrance - probably this should be in a new , separate issue and more of a feature request. What was initially reported works fine now.

As of now, your use case has a workaround too with !important modifier, right?

[patricklafrance]

@atanasster you're right. Sorry I re-opened the issue since in the current state, even if the classes are not strip, it still doesn't do it for us. I will create a separate issue.

For !important, yes and no...

Yes it would work.

No since our docs use the same atomic CSS codebase that we use for our components and our apps. Adding !important to the selectors might cause a lot of regressions.

We could write new selectors for the docs but I would prefer not doing it.

[patricklafrance]

https://github.com/storybookjs/storybook/issues/9190

[shilman]

Jeepers creepers!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.0.0-alpha.11 containing PR #8897 that references this issue. Upgrade today to try it out!

You can find this prerelease on the @next NPM tag.

[shilman]

Gadzooks!! I just released https://github.com/storybookjs/storybook/releases/tag/v5.3.14 containing PR #8897 that references this issue. Upgrade today to try it out!