EnC workspace does not report on generators diagnostics

[jeromelaban]

Version Used: 4.8.0-3.final

Steps to Reproduce:

1. dotnet new blazorwasm -o testblazor01
2. cd testblazor01
3. In testblazor01.csproj add the following:

<AllowUnsafeBlocks>true</AllowUnsafeBlocks>

1. Run dotnet watch
2. In Program.cs, add the following at the end:

 public static partial class Test
 {
     [System.Runtime.InteropServices.JavaScript.JSImport("test")]
     public static partial void Test2(IDisposable test); 
 }

Diagnostic Id: None

Expected Behavior: Hot Reload fails with error SYSLIB1072: The type 'System.IDisposable' is not supported by source-generated JavaScript interop

Actual Behavior: No errors are reported.

[Youssef1313]

cc @davidwengier / @tmat

[jeromelaban]

After investigating a bit further, when a solution change is considered by:

roslyn/src/Features/Core/Portable/EditAndContinue/EditSession.cs

Line 431 in 9367797

var newSourceGeneratedDocumentStates = await newProject.Solution.State.GetSourceGeneratedDocumentStatesAsync(newProject.State, cancellationToken).ConfigureAwait(false);

but the compilation fails in generated code, the failing compilation does not get documents or additional documents added to the list returned by PopulateChangedAndAddedDocumentsAsync. This causes the workspace update to stop and not report diagnostics here:

roslyn/src/Features/Core/Portable/EditAndContinue/EditSession.cs

Lines 898 to 901 in 9367797

	if (projectSummary == ProjectAnalysisSummary.NoChanges)
	{
	continue;
	}

This still has allowed me to find that the delta generation may fail if there are duplicate files in the AdditionalDocuments list (a case not directly related to the repro at the top, but still fails without reporting why).

[tmat]

There might be multiple issues here. First, the diagnostic reported by source generator isn't reported in the IDE:

If you follow the above repro, but instead of dotnet-watch open the project in VS and without running it just add the Test class, the IDE does not show the diagnostics produced by the generator:

The error is only reported when the project is built:

@CyrusNajmabadi

[CyrusNajmabadi]

Are generator diagnostics something we support? I'm not sure how that is supposed to flow into pull diagnostics. Do we need some other IDiagnosticSource for that?

[tmat]

@CyrusNajmabadi Turns out we do have GeneratorDiagnosticsPlaceholderAnalyzer that is special cased all over DiagnosticIncrementalAnalyzer to report the source generator errors :-|. I think this might just be reporting exceptions thrown by generators.

[tmat]

VS reports the diagnostic correctly and right away in Automatic mode. It might take a while in Balanced.