Report line/column when reporting mismatching tags

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorIntermediateNodeWriter.cs

@@ -8,6 +8,7 @@ using System.Text;
 using AngleSharp;
 using AngleSharp.Html;
 using AngleSharp.Parser.Html;
+using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
@@ -286,7 +287,8 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                             {
                                 _scopeStack.CloseScope(
                                     tagName: isComponent ? tagNameOriginalCase : nextTag.Data,
-                                    isComponent: isComponent);
+                                    isComponent: isComponent,
+                                    source: CalculateSourcePosition(node.Source, nextToken.Position));
                                 var closeMethodName = isComponent
                                     ? nameof(RenderTreeBuilder.CloseComponent)
                                     : nameof(RenderTreeBuilder.CloseElement);
@@ -315,6 +317,28 @@ namespace Microsoft.AspNetCore.Blazor.Razor
             }
         }
 
+        private SourceSpan? CalculateSourcePosition(
+            SourceSpan? razorTokenPosition,
+            TextPosition htmlNodePosition)
+        {
+            if (razorTokenPosition.HasValue)
+            {
+                var razorPos = razorTokenPosition.Value;
+                return new SourceSpan(
+                    razorPos.FilePath,
+                    razorPos.AbsoluteIndex + htmlNodePosition.Position,
+                    razorPos.LineIndex + htmlNodePosition.Line - 1,
+                    htmlNodePosition.Line == 1
+                        ? razorPos.CharacterIndex + htmlNodePosition.Column - 1
+                        : htmlNodePosition.Column - 1,
+                    length: 1);
+            }
+            else
+            {
+                return null;
+            }
+        }
+
         private static string GetTagNameWithOriginalCase(string document, HtmlTagToken tagToken)
         {
             var offset = tagToken.Type == HtmlTokenType.EndTag ? 1 : 0; // For end tags, skip the '/'

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/RazorCompilerException.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using Microsoft.AspNetCore.Razor.Language;
 using System;
 
 namespace Microsoft.AspNetCore.Blazor.Razor
@@ -11,16 +12,25 @@ namespace Microsoft.AspNetCore.Blazor.Razor
     /// </summary>
     public class RazorCompilerException : Exception
     {
-        public RazorCompilerException(string message) : base(message)
+        private readonly int _line;
+        private readonly int _column;
+
+        public RazorCompilerException(string message) : this(message, null)
         {
         }
 
+        public RazorCompilerException(string message, SourceSpan? source) : base(message)
+        {
+            _line = source.HasValue ? (source.Value.LineIndex + 1) : 1;
+            _column = source.HasValue ? (source.Value.CharacterIndex + 1) : 1;
+        }
+
         public RazorCompilerDiagnostic ToDiagnostic(string sourceFilePath)
             => new RazorCompilerDiagnostic(
                 RazorCompilerDiagnostic.DiagnosticType.Error,
                 sourceFilePath,
-                line: 1, // Later it might be necessary to take line/col constructor args, but not needed yet
+                line: _line,
-                column: 1,
+                column: _column,
                 message: Message);
     }
 }

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/ScopeStack.cs

@@ -21,19 +21,19 @@ namespace Microsoft.AspNetCore.Blazor.Razor
             _stack.Push(new ScopeEntry(tagName, isComponent));
         }
 
-        public void CloseScope(string tagName, bool isComponent)
+        public void CloseScope(string tagName, bool isComponent, SourceSpan? source)
         {
             if (_stack.Count == 0)
             {
                 throw new RazorCompilerException(
-                    $"Unexpected closing tag '{tagName}' with no matching start tag.");
+                    $"Unexpected closing tag '{tagName}' with no matching start tag.", source);
             }
 
             var expected = _stack.Pop();
             if (!tagName.Equals(expected.TagName, StringComparison.Ordinal))
             {
                 throw new RazorCompilerException(
-                    $"Mismatching closing tag. Found '{tagName}' but expected '{expected.TagName}'.");
+                    $"Mismatching closing tag. Found '{tagName}' but expected '{expected.TagName}'.", source);
             }
 
             // Note: there's no unit test to cover the following, because there's no known way of

test/Microsoft.AspNetCore.Blazor.Build.Test/RazorCompilerTest.cs

@@ -525,7 +525,14 @@ namespace Microsoft.AspNetCore.Blazor.Build.Test
         {
             // Arrange/Act
             var result = CompileToCSharp(
-                "<root><other />text<child>more text</root></child>");
+                $"@{{\n" +
+                $"   var abc = 123;\n" +
+                $"}}\n" +
+                $"<root>\n" +
+                $"    <other />\n" +
+                $"    text\n" +
+                $"    <child>more text</root>\n" +
+                $"</child>\n");
 
             // Assert
             Assert.Collection(result.Diagnostics,
@@ -533,6 +540,8 @@ namespace Microsoft.AspNetCore.Blazor.Build.Test
                 {
                     Assert.Equal(RazorCompilerDiagnostic.DiagnosticType.Error, item.Type);
                     Assert.StartsWith("Mismatching closing tag. Found 'root' but expected 'child'.", item.Message);
+                    Assert.Equal(7, item.Line);
+                    Assert.Equal(21, item.Column);
                 });
         }