Generate Blazor control class from Roslyn generator

[GLuca74]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I’m writing my first Roslyn-based code generator. The goal of the generator is, when certain conditions are met, to write a Blazor component and a related class, and make them available to the user. Currently, the component is generated, and Visual Studio’s editor recognizes it without issues, but at build time the control is not recognized. The Output window shows:

warning RZ10012: Found markup element with unexpected name [...]. If this is intended to be a component, add a @using directive for its namespace.

I’ve prepared a solution to reproduce the issue, available at https://github.com/GLuca74/TestRoslyn.

The solution consists of:

• Default templates for .NET MAUI Blazor Hybrid and Web App (TestRoslyn, TestRoslyn.Shared, TestRoslyn.Web, TestRoslyn.Web.Client)

• TestRoslyn.RCL, which references TestRoslyn.Generator and contains the base control (TestComponent.razor) from which the generated control should inherit:

@typeparam T

<h3>TestComponent</h3>
<span>@typeof(T).FullName</span>

@code {

}

• TestRoslyn.Generator
  This project contains the generator that will produce the control to be made available to the user.
  In this project, the MyGenerator class works as follows: if it finds a class in the consumer project whose name starts with TestClass, it generates a component and a corresponding class based on the rest of the name. For example, in TestRoslyn.Shared there is a class TestClassA. In this case, the generator produces:

namespace TestRoslyn.Shared
{
    public class AComponent : TestRoslyn.RCL.TestComponent<AClass>
    {
    }

    public class AClass
    {
    }
}

In the Counter page, I added the component:

<AComponent/>

Visual Studio’s editor recognizes the control and does not report any issues. However, when I run the application, I get the warning:

warning RZ10012: Found markup element with unexpected name 'AComponent'. If this is intended to be a component, add a @using directive for its namespace.

The app still runs, and inspecting with debugging tools, the control is rendered in both the WebApp and the MAUI app just as:

<acomponent></acomponent>

To verify that the base component works, I also added the class ManualComponent in the TestRoslyn.Shared project:

public class ManualComponent : TestRoslyn.RCL.TestComponent<AClass>
{
}

ManualComponent renders without any issues.

So the problem seems to be that the generated component AComponent is not visible to the compiler at build time. Is there a way to overcome this and make AComponent available to the compiler?

Thanks!

Expected Behavior

The generated component AComponent should be fully recognized by the compiler and the Blazor runtime, just like a manually created component.

Steps To Reproduce

https://github.com/GLuca74/TestRoslyn

Exceptions (if any)

No response

.NET Version

9.0.304

Anything else?

No response

[MihuBot]

I'm a bot. Here are possible related and/or duplicate issues (I may be wrong):

• Razor Components which are added by a 3rd party source generator do not render if they are added to a razor file using markup syntax. #32253
• Unable to use Blazor components in source generators #32949

[GLuca74]

So the current situation is that Razor performs its work inside an analyzer, and each analyzer is self-contained and cannot see the work done by other analyzers.
The idea of having a mechanism that allows specifying that one analyzer should run before or after another one is not very well received.

The least burdensome workaround for users of the generator is to add
<UseRazorSourceGenerator>false</UseRazorSourceGenerator>
so that Razor’s work is executed outside of a source generator.

Besides getting back the AppName.Views.dll assembly, are there any features or optimizations lost when disabling UseRazorSourceGenerator?