Check for RequiredAttribute when rendering fragment

[linkdotnet]

.NET 6 introduced the usage of the RequiredAttribute which gives you a nice little warning when the required parameter was not provided for your component. Due to the nature of how the component is built in unit tests, this falls short.
Therefore it would be nice to get an exception if not provided. At least the explicitly enable this behavior if wished.

IRenderedComponent<TComponent> RenderComponent<TComponent> Action<ComponentParameterCollectionBuilder<TComponent>> parameterBuilder, bool throwWhenRequiredParameterNotSet 	= false)

A small reference implementation (without the optional toggle) can be found here (including a test).

A bit more context can be found on the official Microsoft site.

[egil]

Hi Steven,

The EditorRequired works only at design time (e.g. in a supported editor afaik), which is why I decided not to add explicit support for it, since bUnit would be doing checks that Blazor doesn't do at runtime.

Also, you could argue that you should be writing tests covering the cases where the "editor required" parameters are null.

That said, I'm not opposed to adding that flag to the RenderComponent and Render methods, but I need to understand the use case a bit more.

[linkdotnet]

Hi Egil,

My reasoning goes into the direction that under normal circumstances (using a blazor component) you would get the hint from the compiler.
Constructing them via RenderFragment wouldn’t result in a hint.

But yes maybe a bit to specific. Thanks for your insights.

Cheers
Steven

[egil]

I dont know if you have tried it, but if you write tests in .razor files, and define the component under test using inline render fragments, then Im pretty sure the compiler will give you this warning as well, e.g.:

var cut = Render(@<MyComp SomeProp="foo" />);

Have you tried that?

[linkdotnet]

Ah no I didn’t know that. Very helpful indeed. Thanks

[egil]

There are a few things you need to do to write tests in .razor files, but give it a try and report back: https://bunit.dev/docs/getting-started/writing-tests.html#creating-basic-tests-in-razor-files

It is by far my favorite way of writing tests, even if the VS editor experience with .razor files is a bit bonkers at times.