Pass content to dynamic block render functions

[westonruter]

Currently only the attributes are passed to the PHP render function. This PR changes that to allow the contents of the block also to be passed. This brings blocks closer aligned with shortcodes, for which the callback functions take two arguments, the attributes and the content.

[youknowriad]

The reason why the content was not passed is because the render function is needed for dynamic blocks (server side rendered) and their content is not "important" and is considered a fallback content only.

But I guess, this addition does no harm?
Do you think of real use-cases where the content would be used in the render function?

[westonruter]

One use case could be for a dynamic block reading content would be for something like a chart block which has content that is CSV data that is needed for rendering the chart and accompanying table on the server.

[youknowriad]

To be clear, I'm not against this I'm just trying to figure out when will we use this exactly.

That said, I think the content should always be HTML, we can't really store CSV there and a JSON seems a better approach for this.

[westonruter]

OK, an HTML table then can be the content 😄

I got a separate request for this in a DM in Slack. I've asked them to respond here with the use case as well.

[willybahuaud]

Hello!

Here is an use case, using dropCap with the text bloc:

<!-- wp:core/text dropCap="true" -->
<p>fzefqzfqzf</p>
<!-- /wp:core/text -->

[westonruter]

So in that case, the PHP rendering function would inject a dropCap class name on the first <p> or wrap the block's contents in a div element that can be targeted by CSS to apply the style.

[westonruter]

Rebased to fix merge conflict. Former HEAD was 86b1ee8.

[coveralls]

Coverage remained the same at 17.816% when pulling 2ca96f9 on update/pass-content-to-php-render-function into 4564ee0 on master.

[youknowriad]

For consistency, It's probably better to pass the content to the render function but for the dropCap use case, it should be done in the save function IMO