[Proposal] Performance/usability improvements for analyzer tests

src/Framework/AspNetCoreAnalyzers/test/Extensions/CSharpAnalyzerTestExtensions.cs

@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Analyzers.Verifiers;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Testing;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Testing;
+
+namespace Microsoft.AspNetCore.Analyzers;
+
+public static class CSharpAnalyzerTestExtensions
+{
+    extension<TAnalyzer, TVerifier>(CSharpAnalyzerTest<TAnalyzer, TVerifier>)
+        where TAnalyzer : DiagnosticAnalyzer, new()
+        where TVerifier : IVerifier, new()
+    {
+        public static CSharpAnalyzerTest<TAnalyzer, TVerifier> Create([StringSyntax("C#-test")] string source, params ReadOnlySpan<DiagnosticResult> expectedDiagnostics)
+        {
+            var test = new CSharpAnalyzerTest<TAnalyzer, TVerifier>
+            {
+                TestCode = source.ReplaceLineEndings(),
+                // We need to set the output type to an exe to properly
+                // support top-level programs in the tests. Otherwise,
+                // the test infra will assume we are trying to build a library.
+                TestState = { OutputKind = OutputKind.ConsoleApplication },
+                ReferenceAssemblies = CSharpAnalyzerVerifier<TAnalyzer>.GetReferenceAssemblies(),
+            };
+
+            test.ExpectedDiagnostics.AddRange(expectedDiagnostics);
+            return test;
+        }
+    }
+
+    public static CSharpAnalyzerTest<TAnalyzer, TVerifier> WithSource<TAnalyzer, TVerifier>(this CSharpAnalyzerTest<TAnalyzer, TVerifier> test, [StringSyntax("C#-test")] string source)
+        where TAnalyzer : DiagnosticAnalyzer, new()
+        where TVerifier : IVerifier, new()
+    {
+        test.TestState.Sources.Add(source);
+        return test;
+    }
+}

src/Framework/AspNetCoreAnalyzers/test/Verifiers/CSharpAnalyzerVerifier.cs

@@ -2,15 +2,16 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.AspNetCore.Builder;
-using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.InternalTesting;
+using Microsoft.AspNetCore.Mvc;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Testing;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Testing;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.AspNetCore.Hosting;
 
 namespace Microsoft.AspNetCore.Analyzers.Verifiers;
 
@@ -30,19 +31,9 @@ public static DiagnosticResult Diagnostic(DiagnosticDescriptor descriptor)
         => CSharpAnalyzerVerifier<TAnalyzer, DefaultVerifier>.Diagnostic(descriptor);
 
     /// <inheritdoc cref="AnalyzerVerifier{TAnalyzer, TTest, TVerifier}.VerifyAnalyzerAsync(string, DiagnosticResult[])"/>
-    public static async Task VerifyAnalyzerAsync(string source, params DiagnosticResult[] expected)
+    public static async Task VerifyAnalyzerAsync([StringSyntax("C#-test")] string source, params DiagnosticResult[] expected)
     {
-        var test = new CSharpAnalyzerTest<TAnalyzer, DefaultVerifier>
-        {
-            TestCode = source.ReplaceLineEndings(),
-            // We need to set the output type to an exe to properly
-            // support top-level programs in the tests. Otherwise,
-            // the test infra will assume we are trying to build a library.
-            TestState = { OutputKind = OutputKind.ConsoleApplication },
-            ReferenceAssemblies = GetReferenceAssemblies(),
-        };
-
-        test.ExpectedDiagnostics.AddRange(expected);
+        var test = CSharpAnalyzerTest<TAnalyzer, DefaultVerifier>.Create(source, expected);
         await test.RunAsync(CancellationToken.None);
     }