public void Execute_CombinesErrorsOnRewritingErrors() { // Arrange var engine = RazorEngine.Create(builder => { builder.AddTagHelpers(new[] { CreateTagHelperDescriptor( tagName: "form", typeName: "TestFormTagHelper", assemblyName: "TestAssembly"), CreateTagHelperDescriptor( tagName: "input", typeName: "TestInputTagHelper", assemblyName: "TestAssembly"), }); }); var phase = new DefaultRazorTagHelperBinderPhase() { Engine = engine, }; var content = @" @addTagHelper *, TestAssembly <form> <input value='Hello' type='text' />"; var sourceDocument = TestRazorSourceDocument.Create(content, filePath: null); var codeDocument = RazorCodeDocument.Create(sourceDocument); var originalTree = RazorSyntaxTree.Parse(sourceDocument); var initialError = RazorDiagnostic.Create( new RazorDiagnosticDescriptor("RZ9999", () => "Initial test error", RazorDiagnosticSeverity.Error), new SourceSpan(SourceLocation.Zero, contentLength: 1)); var expectedRewritingError = RazorDiagnosticFactory.CreateParsing_TagHelperFoundMalformedTagHelper( new SourceSpan(new SourceLocation(Environment.NewLine.Length * 2 + 30, 2, 1), contentLength: 4), "form"); var erroredOriginalTree = RazorSyntaxTree.Create(originalTree.Root, originalTree.Source, new[] { initialError }, originalTree.Options); codeDocument.SetSyntaxTree(erroredOriginalTree); // Act phase.Execute(codeDocument); // Assert var outputTree = codeDocument.GetSyntaxTree(); Assert.Empty(originalTree.Diagnostics); Assert.NotSame(erroredOriginalTree, outputTree); Assert.Equal(new[] { initialError, expectedRewritingError }, outputTree.Diagnostics); }