Blazor FocusAsync coverage

[guardrex]

Fixes #20232
Fixes #20195

[guardrex]

@captainsafia I was trying not to change Javier's lingo too much, but I agree with you. It's much better to just rewrite it to avoid the versioning altogether. Also, it was 😵 half-baked 😵 ... I didn't have all of the focus event-based example converted over to a click-based event example, which is necessary now that Blazor has a nice way to focus things without custom JS interop.

Also, I think prefixing objects/members with my isn't so hot. I'm still playing with a general naming approach to avoid my, but perhaps example as a prefix is good (e.g., myInput 👉 exampleInput, mybutton 👉 exampleButton) ... it's on this PR to see how it composes. If you have a better idea, I'm all 👂👂👂.

[guardrex]

Also @captainsafia ... one more little thing that we can put on here for issue #20195.

@mrlife inquired on the "guarantee" in the reasoning for not being able to pass element references between components. I think what that "guarantee" means is that the element reference doesn't exist until the component is rendered ... therefore ... that late in rendering the component ... nothing can be passed as a parameter. Thus (along with being a struct), the guidance is to use a callback.

I change that text here on the last commit to try and fix up the "guarantee" lingo to explain it that way. See if that update makes sense to u.

@mrlife, please review that last commit.

ADDITIONAL: I'm going to make one more little update to the struct remark. See if that works, too.

[captainsafia]

Looking pretty good!

Tangentially: do we have docs on our updated IJSObjectReference stuff?

[guardrex]

@captainsafia

do we have docs on our updated IJSObjectReference stuff?

Yes ... it's in the 5.0 version of the doc at ...

https://docs.microsoft.com/en-us/aspnet/core/blazor/call-javascript-from-dotnet?view=aspnetcore-5.0#blazor-javascript-isolation-and-object-references

... also mentioned here (and Pranav said this is enough here, i.e., we don't need an example for this mention) ...

https://docs.microsoft.com/en-us/aspnet/core/blazor/webassembly-performance-best-practices?view=aspnetcore-5.0#consider-making-synchronous-calls

[guardrex]

🙈😄

await exampleInput.FocusAsync();

"FocusAsync" ....... Async!! .... await .... Geebers McScreebers! 😄

One of these days, I'll learn how to do async. Not today, of course! ... but one day. 😁

[guardrex]

@captainsafia ... I committed ur updates. I think we're good here. This won't go live until later today/tonight, so we have time to sneak another PR in if needed.