RFC 66: EnumBlock

[kaedroho]

Rendered

[kaedroho]

We discussed this at the team meeting today. Nobody objected to the idea in principle, but @gasman thought the name would be confusing.

The name comes from Rust's enum type, but maybe that was a bad idea since enums are usually a mapping of symbols to numbers in other languages.

Any thoughts on UnionBlock? (following C's union type) or any other ideas?

[loicteixeira]

SwitchBlock or CaseBlock 🤷‍♂️

[kaedroho]

Planning on closing this one, it didn't exactly get a very enthusiastic response when I presented it so I'm going to focus on other things

[kaedroho]

Reopening as I feel like this is a missing piece in our set of block types and I'd like to push for it to be included in Wagtail!

I think there are three fundamental data structures that should make up a StreamField:

• A way to manage a sequence of blocks of the same type (ListBlock)
• A way to manage a set of blocks that appear together (StructBlock)
• A way to manage a choice between multiple types (UnionBlock)

Adding UnionBlock, would mean that Wagtail gains a new useful block type, and we could also redefine StreamBlock in terms of these block types. For example:

StreamBlock([
    ('type_a', TypeABlock()),
    ('type_b', TypeBBlock()),
])

ListBlock(UnionBlock([
    ('type_a', TypeABlock()),
    ('type_b', TypeBBlock()),
]))

This would mean all sequences are managed by the same type. I'm not saying that we should drop support forStreamBlock as it provides the stream UI, but the internal data structure could be managed by ListBlock instead.

A use for UnionBlock on its own could be as a way to define a link that could be either a page chooser or a URL:

class LinkedImageBlock(StructBlock):
    image = ImageChooserBlock()
    link = UnionBlock([
        ('internal', PageChooserBlock()),
        ('external', URLBlock()),
    ])

[kaedroho]

Closing in favor of #94 which seems to be the same idea with a much better RFC. Great work @jams2!

[jams2]

Thanks @kaedroho - I missed this when I started writing #94, I will review it properly before responding to feedback there.