Code Action: Simplify Component tag to self-closing if body is empty and no child `RenderFragment` is required

[Peter-Juhasz]

It would help refactor this:

<Component Attribute="Value">
    
</Component>

To this:

<Component Attribute="Value" />

If the following conditions are met:

• Markup element is a tag helper for a Component
• It doesn't have any Attribute of type RenderFragment or RenderFragment<T> marked with EditorRequired (+ which is not bound via a markup attribute syntax (instead of body template))
• It is not self-closed yet
• Its body contains only whitespace

If accepted, I already have a draft working implementation for this in my fork/branch:
https://github.com/Peter-Juhasz/razor/blob/simplifytagtoselfclosing/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/Razor/SimplifyTagToSelfClosingCodeActionProvider.cs

[phil-allen-msft]

I believe this change will need some tests to verify the conditions, in particular the second conditions.

[davidwengier]

Random thought about looking for RenderFragment with EditorRequired, I think if there is ChildContent attribute we would need to not offer the code action, even if its not requred, as the whitespace means it's being specified, and strictly speaking the code action would be removing it.

Though whether that whitespace content is important or necessary is an open question.

[davidwengier]

Oh, one other thought: It is much easier (at least IMO) to create tests for this in the "cohosting" test files, eg: https://github.com/dotnet/razor/blob/release/dev17.14/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CodeActions/ExtractToComponentTests.cs#L11. You would need to create a new file for your code action of course, but the rest should be pretty straightforward hopefully. The non-cohosting tests have a lot more setup and mocks involved which might get annoying.

[Peter-Juhasz]

Thanks @davidwengier for pointing to that test infrastructure, it was easy to use.

I opened a PR.