Feature request: Support server-side rendering of non-standard DOM attribute names (eg. AMP's [prop]="value")

[cole-sanderson]

Do you want to request a feature or report a bug?
Request a feature

I am working on project to build AMP page with React Server Side Rendering. I am having an issue to add custom attribute to built-in AMP element. In order to be able to use amp-bind we need to be able to output “bindings”, which are special attributes of the form [attribute], eg. [slide]="selectedSlide".

<amp-carousel 
    layout={layout}
    height={height}
    width={width}
    [slide]={slide}
>
        ...
</amp-carousel>

Here is AMP carousel example that work with amp-bind.

What is the current behavior?

• Parsing error: Unexpected token [ (Fatal)

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

• All

For more information, you can read all the discussion in this PR.

[aweary]

Thanks for the request @cole-sanderson! Once #7311 is merged this should be possible, with a caveat. The error you're getting:

- Parsing error: Unexpected token [ (Fatal)

Is because [slide]={slide} is not valid JSX, so parsing fails. I think it's unlikely that the JSX spec would be updated to support this syntax unless it would provide some benefit for a broader scope of issues/features.

What that means is that you'll just need to use the regular function call syntax for elements that require these AMP attributes.

React.createElement('amp-carousel', {
  layout: layout,
  height: height,
  width: width,
  '[slide]': slide
}

After #7311 is merged the server renderer will not blacklist the [slide] property and the markup should be rendered correctly.

Keep in mind this is only for server-side rendering. [slide] is not a valid DOM attribute name, so if you're intention is to hydrate this server-rendered markup on an AMP page with React it won't work. Though I assume AMP will manage the content on the client, so that might not even be a concern.

[aweary]

The solution outlined above should now work with React 16.

[cole-sanderson]

Awesome, thank you @aweary! 😀

[kschmidtdev]

@aweary according to https://reactjs.org/blog/2017/09/08/dom-attributes-in-react-16.html#changes-in-detail there isn't support for custom DOM elements (amp-carousel) with custom attributes (slide). I've tried the createElement call in react server-side rendering with no success. Can you confirm?

[aweary]

hey @kschmidtdev, you are correct. The server renderer still restricts attributes using isAttributeNameSafe. I don't remember why I thought this had changed in React 16, but neither #7311 nor it's successor #10385 change this behavior.

I'll re-open this. I'm not sure what the solution here would be; it's unfortunate that AMP uses non-standard attribute names. If server rendering AMP components is a common use case then we could potentially fork isAttributeNameSafe to a version that allows attributes with leading/trailing brackets on custom elements.

@gaearon what do you think?

[svdoever]

Would really appreciate a solution for this. Doing server-side AMP rendering as well using react. Will never dehydrate on client.

[dfrankland]

Just to add to the confusion, you can still add attributes with square brackets to non-custom components:

Example:

• JS

  const customProps = {
    "[custom-property]": "Hello, world!"
  };

• JSX

  <div>
    <div {...customProps}>Test</div>
    <custom-component {...customProps}>Test</custom-component>
  </div>

• Resulting HTML

  <div data-reactroot="">
    <div [custom-property]="Hello, world!">Test</div>
    <custom-component>Test</custom-component>
  </div>

This throws a warning only for the <custom-component />.

[dfrankland]

I've opened #12568 to add the ability to, at the very least, server-render non-standard components with non-standard attributes (like AMP).

[westonruter]

For amp-bind there is now an XML-compatible syntax, so you can do data-amp-bind-foo="bar" as an alternative to [foo]="bar". See ampproject/amphtml#11115 and ampproject/amphtml#15408. So it doesn't seem that support for the amp-bind bracketed attribute syntax would be required in React.

[aweary]

Great! In that case I don't think it's worth the effort to support the XML-incompatible syntax.