dcc.Link: Use `href` as `children` if no children are defined

[Marc-Andre-Rivet]

With HTML anchors, users are forced to provide a displayed content for the anchor, which can be as simple as the href itself..

<a href='myurl'>myurl</a>

1:1 correspondance in dcc.Link forces users to do the same thing:

dcc.Link(
  href='myurl',
  children=['myurl']
)

Defaulting to href for inner content if no children is defined provides a default behavior that will be acceptable in certain situations and will simplify usage.

[alexcjohnson]

Perhaps the other way as well, use children as href - that way you can do dcc.Link(myurl) and it'll behave reasonably.

[Marc-Andre-Rivet]

It's possible to use anything as a dcc.Link child and the whole thing becomes clickable, so while href is a string and can be used safely as a child, the same can't be said about children.

    dcc.Link(
        href='/sub-path',
        refresh=True,
        children=[html.Div('Hello'), html.Div('World')]
    ),

[alexcjohnson]

sure, but if children happens to be just a string, we might as well copy it back to href.

[Marc-Andre-Rivet]

Yes. But it lends itself to a if..else.. logic that can be confusing for a user. The href being guaranteed to be there and to be a string, it does not suffer from the same limitations / branching. Not opposed per-say, just want to make sure we agree on the limitations / logic leakage if we decide to support it.

Side-note: href is not currently required. A dcc.Link without href makes no sense, I propose to mark it as isRequired / the old behavior being considered a bug, not a breaking change.

[alexcjohnson]

Fair enough - and it could be confusing if you start with just children and want to switch to different text/elements - you have to make two changes: move the children string into href and then provide the new children. Then we can also do #773 🎉