Fix VSTHRD010 code fix crash in async lambdas

src/Microsoft.VisualStudio.Threading.Analyzers.CodeFixes/VSTHRD010MainThreadUsageCodeFix.cs

@@ -62,8 +62,11 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
         Regex lookupKey = (container.IsAsync || convertToAsync)
             ? CommonInterest.FileNamePatternForMethodsThatSwitchToMainThread
             : CommonInterest.FileNamePatternForMethodsThatAssertMainThread;
-        string[]? options = diagnostic.Properties[lookupKey.ToString()]?.Split('\n');
-        if (options?.Length > 0)
+        string[] options = diagnostic.Properties[lookupKey.ToString()]?
+            .Split('\n')
+            .Where(option => !string.IsNullOrWhiteSpace(option))
+            .ToArray() ?? Array.Empty<string>();
+        if (options.Length > 0)
         {
             // For any symbol lookups, we want to consider the position of the very first statement in the block.
             int positionForLookup = container.BlockOrExpression.GetLocation().SourceSpan.Start + 1;

test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD010MainThreadUsageAnalyzerTests.cs

@@ -870,6 +870,66 @@ async Task F() {
         await CSVerify.VerifyAnalyzerAsync(test);
     }
 
+    [Fact]
+    public async Task InvokeVsSolutionAfterSwitchedToMainThreadAsyncInAnonymousMethod()
+    {
+        var test = @"
+using Microsoft.VisualStudio.Shell.Interop;
+using Microsoft.VisualStudio.Threading;
+
+namespace Microsoft.VisualStudio.Shell.Interop {
+    interface IVsInvokablePrivate {
+        int Invoke();
+    }
+}
+
+class Test {
+    private JoinableTaskContext joinableTaskContext;
+
+    int Invoke(IVsInvokablePrivate invokable) {
+        return this.joinableTaskContext.Factory.Run(async delegate {
+            await this.joinableTaskContext.Factory.SwitchToMainThreadAsync();
+            return invokable.Invoke();
+        });
+    }
+}
+";
+        await CSVerify.VerifyAnalyzerAsync(test);
+    }
+
+    [Fact]
+    public async Task CodeFixWithNoMainThreadSwitchingMethodsInAnonymousMethod()
+    {
+        var test = @"
+using System;
+using System.Threading.Tasks;
+
+namespace TestNS {
+    interface IThreadAffinitized {
+        int Invoke();
+    }
+}
+
+class Test {
+    void F(TestNS.IThreadAffinitized value) {
+        Func<Task<int>> callback = async delegate {
+            await Task.Yield();
+            return value.Invoke();
+        };
+    }
+}
+";
+        var verifier = new CSVerify.Test
+        {
+            TestCode = test,
+            ExpectedDiagnostics = { CSVerify.Diagnostic(DescriptorAsync).WithSpan(15, 26, 15, 32).WithArguments("IThreadAffinitized") },
+            FixedCode = test,
+        };
+        verifier.TestState.AdditionalFilesFactories.Clear();
+        verifier.TestState.AdditionalFiles.Add(("vs-threading.MembersRequiringMainThread.txt", "[TestNS.IThreadAffinitized]"));
+        await verifier.RunAsync();
+    }
+
     [Fact]
     public async Task InvokeVsSolutionInLambda()
     {