Blazor input component support when EditContext is not supplied

[MackinnonBuck]

Blazor input component support when EditContext is not supplied

This PR enables Blazor input component functionality (InputText, InputSelect, etc.) when no EditContext is provided by a parent EditForm.

PR Description

The current approach solves the issue by allowing InputBase.EditContext to be null. Validation styling won't be applied to input components without an EditContext.

Fixes #27804

[MackinnonBuck]

Something else to consider: Do we want validation styling to apply to input components without a parent EditForm? The validation css class will always be either valid or modified valid, but this is meaningless since data annotations are ignored in these cases.

Update: One case I forgot about is if the input's current value cannot be converted to the desired type, in which case the css class would be modified invalid. So there could be an argument for keeping validation styling.

[pranavkm]

but it has the crucial drawback that Inputbase<>.EditContext is part of the public API surface and marking it as nullable would be a breaking change

We've been playing somewhat loosey with nullable annotations as we work thru the repo. One could further argue that the current annotations are incorrect to begin with given if you create a new component, the edit context is null even though the compiler says otherwise:

ie..

var inputText = new InputText();
Console.WriteLine(inputText.EditContext.ToString()); // The compiler will claim this is null safe, even though we know this will null-ref

How does it look if we make EditContext nullable and let it be null in some cases?

[MackinnonBuck]

We've been playing somewhat loosey with nullable annotations as we work thru the repo.

Good to know - I'll give the other approach a go.

[MackinnonBuck]

@pranavkm I've updated the implementation to allow EditContext to be null. Also, my previous comment...

Something else to consider: Do we want validation styling to apply to input components without a parent EditForm?

...is no longer relevant because validation styling won't happen without an edit context. It's probably better this way, since validation styling would just get in the way if no actual validation was happening.

[MackinnonBuck]

I've only added tests verifying that InputSelect and InputRadioGroup work without a parent EditForm, since they contain most of the unique logic of the input components (other logic comes from InputBase). InputRadioGroup is a bit special in that it still calculates its own styling. The InputSelect test verifies that complicated binding scenarios still work (binding to arrays, boolean values).

[MackinnonBuck]

It also appears that the CI is a bit unhappy that the baseline API files are getting modified (by making InputBase<>.EditContext nullable). We would have to make some exception for this (or revert the nullability of EditContext).

[pranavkm]

Looks great. @javiercn could you have a look since you said you did something similar?