Fix reporting of incorrect RazorLangVersion (#9605)

* Add a test

* Fix handling of incorrect razor lang version

Author: jjonescz

src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/IncrementalValueProviderExtensions.cs

@@ -28,8 +28,8 @@ internal static IncrementalValuesProvider<TSource> ReportDiagnostics<TSource>(th
         {
             context.RegisterSourceOutput(source, (spc, source) =>
             {
-                var (sourceItem, diagnostic) = source;
-                if (sourceItem == null && diagnostic != null)
+                var (_, diagnostic) = source;
+                if (diagnostic != null)
                 {
                     spc.ReportDiagnostic(diagnostic);
                 }
@@ -42,8 +42,8 @@ internal static IncrementalValueProvider<TSource> ReportDiagnostics<TSource>(thi
         {
             context.RegisterSourceOutput(source, (spc, source) =>
             {
-                var (sourceItem, diagnostic) = source;
-                if (sourceItem == null && diagnostic != null)
+                var (_, diagnostic) = source;
+                if (diagnostic != null)
                 {
                     spc.ReportDiagnostic(diagnostic);
                 }

src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.RazorProviders.cs

@@ -31,7 +31,7 @@ public partial class RazorSourceGenerator
             globalOptions.TryGetValue("build_property.SupportLocalizedComponentNames", out var supportLocalizedComponentNames);
             globalOptions.TryGetValue("build_property.GenerateRazorMetadataSourceChecksumAttributes", out var generateMetadataSourceChecksumAttributes);
 
-            var razorLanguageVersion = RazorLanguageVersion.Latest;
+            RazorLanguageVersion razorLanguageVersion;
             Diagnostic? diagnostic = null;
             if (!globalOptions.TryGetValue("build_property.RazorLangVersion", out var razorLanguageVersionString) ||
                 !RazorLanguageVersion.TryParse(razorLanguageVersionString, out razorLanguageVersion))
@@ -40,6 +40,7 @@ public partial class RazorSourceGenerator
                     RazorDiagnostics.InvalidRazorLangVersionDescriptor,
                     Location.None,
                     razorLanguageVersionString);
+                razorLanguageVersion = RazorLanguageVersion.Latest;
             }
 
             var razorConfiguration = RazorConfiguration.Create(razorLanguageVersion, configurationName ?? "default", System.Linq.Enumerable.Empty<RazorExtension>(), true);

src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTests.cs

@@ -2811,5 +2811,26 @@ @namespace MyApp.Pages
             Assert.Empty(result.Diagnostics);
             Assert.Equal(2, result.GeneratedSources.Length);
         }
+
+        [Theory, CombinatorialData]
+        public async Task RazorLangVersion_Incorrect([CombinatorialValues("incorrect", "-1", "10000")] string langVersion)
+        {
+            var project = CreateTestProject(new()
+            {
+                ["Pages/Index.razor"] = "<h1>Hello world</h1>",
+            });
+            var compilation = await project.GetCompilationAsync();
+            var driver = await GetDriverAsync(project, options =>
+            {
+                options.TestGlobalOptions["build_property.RazorLangVersion"] = langVersion;
+            });
+
+            var result = RunGenerator(compilation!, ref driver);
+
+            result.Diagnostics.Verify(
+                // error RZ3600: Invalid value '{0}'' for RazorLangVersion. Valid values include 'Latest' or a valid version in range 1.0 to 8.0.
+                Diagnostic("RZ3600").WithArguments(langVersion).WithLocation(1, 1));
+            Assert.Single(result.GeneratedSources);
+        }
     }
 }