feat: include children info in xblock api

[rayzhou-bit]

This change will send children info for when the xblock api is called with /xblock/{blockId}?fields=childrenInfo. This was created to allow the Library Content Editor Block to access the blocks of its selected library. The frontend PR can be found here: openedx/frontend-lib-content-components#411

Example:
GET http://localhost:18010/xblock/block-v1:edX+DemoX+Demo_Course+type@library_content+block@10391c53c21b4f439c1f3aed3525be89?fields=childrenInfo

returns:

{
  "children": [
    {
      "id": "block-v1:edX+DemoX+Demo_Course+type@html+block@ff2da4992821e87349f9",
      "display_name": "Text",
      "category": "html",
      "has_children": false
    }
  ]
}

[connorhaugh]

that are selected for it.

For others reading this: You mean are its children. The "selected" word here means something else.
I'll take a look.

[kdmccormick]

We can't be hard-coding special cases for the library_content block, or any other XBlock type, unless it's absolutely necessary. Is there a way you can get this API to return the data you need that doesn't involve an if LibraryContentBlock conditional?

[rayzhou-bit]

@kdmccormick I was looking at a _create_xblock_child but it called create_xblock_info which in turn called _create_xblock_child again. I'll have another look after lunch.

[connorhaugh]

The way to do it would be to actually include the include_children_predicate in the request object (you will have to make a new url in the urls.py file I believe), and then have its presence dictate whether the children are included.

[kdmccormick]

A couple small requests, then this should be good to go.

I haven't manually tested yet and there are no unit tests, so I trust you have manually tested it.

[kdmccormick]

Suggested change

include_child_info=False,

unused parameter?

[rayzhou-bit]

Ty, I forgot to take this back out

[kdmccormick]

Suggested change

category = getattr(xblock, "category", "")

unused variable?

[rayzhou-bit]

forgot to remove this as well

[kdmccormick]

Looks better, thanks 👍🏻

[kdmccormick]

Looks good. My only request is that when you squash & merge, please beef up your commit message a bit.

This change will send child info when the xblock api is called. This allows the Library Content Editor Block to see the blocks that are selected for it.

What is the URL of this API? Does the new info require a new query param? Where is the corresponding frontend PR? Those are the sort of questions another dev would be thinking when they read your commit.