From 687b3f691167ac29361db161fd7e0427652e0a0d Mon Sep 17 00:00:00 2001
From: Ajay Bhargav Baaskaran <ajbaaska@microsoft.com>
Date: Thu, 4 Aug 2016 14:48:25 -0700
Subject: [PATCH] [Fixes #815] Fix Debug.Assert failure for malformed tags in
 expression

---
 .../Internal/TagHelperParseTreeRewriter.cs    | 20 ++++++++------
 .../TagHelperParseTreeRewriterTest.cs         | 27 +++++++++++++++++++
 2 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Razor/Parser/TagHelpers/Internal/TagHelperParseTreeRewriter.cs b/src/Microsoft.AspNetCore.Razor/Parser/TagHelpers/Internal/TagHelperParseTreeRewriter.cs
index ee17ca334c..925d4d146c 100644
--- a/src/Microsoft.AspNetCore.Razor/Parser/TagHelpers/Internal/TagHelperParseTreeRewriter.cs
+++ b/src/Microsoft.AspNetCore.Razor/Parser/TagHelpers/Internal/TagHelperParseTreeRewriter.cs
@@ -60,12 +60,12 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
 
         public void Rewrite(RewritingContext context)
         {
-            RewriteTags(context.SyntaxTree, context);
+            RewriteTags(context.SyntaxTree, context, depth: 0);
 
             context.SyntaxTree = _currentBlock.Build();
         }
 
-        private void RewriteTags(Block input, RewritingContext context)
+        private void RewriteTags(Block input, RewritingContext context, int depth)
         {
             // We want to start a new block without the children from existing (we rebuild them).
             TrackBlock(new BlockBuilder
@@ -93,7 +93,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
                             // Non-TagHelper tag.
                             ValidateParentAllowsPlainTag(childBlock, context.ErrorSink);
 
-                            TrackTagBlock(childBlock);
+                            TrackTagBlock(childBlock, depth);
                         }
 
                         // If we get to here it means that we're a normal html tag.  No need to iterate any deeper into
@@ -102,7 +102,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
                     else
                     {
                         // We're not an Html tag so iterate through children recursively.
-                        RewriteTags(childBlock, context);
+                        RewriteTags(childBlock, context, depth + 1);
                         continue;
                     }
                 }
@@ -133,7 +133,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
             BuildCurrentlyTrackedBlock();
         }
 
-        private void TrackTagBlock(Block childBlock)
+        private void TrackTagBlock(Block childBlock, int depth)
         {
             var tagName = GetTagName(childBlock);
 
@@ -148,6 +148,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
                 var parentTracker = _trackerStack.Count > 0 ? _trackerStack.Peek() : null;
                 if (parentTracker != null &&
                     !parentTracker.IsTagHelper &&
+                    depth == parentTracker.Depth &&
                     string.Equals(parentTracker.TagName, tagName, StringComparison.OrdinalIgnoreCase))
                 {
                     PopTrackerStack();
@@ -157,7 +158,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
             {
                 // If it's not a void element and it's not self-closing then we need to create a tag
                 // tracker for it.
-                var tracker = new TagBlockTracker(tagName, isTagHelper: false);
+                var tracker = new TagBlockTracker(tagName, isTagHelper: false, depth: depth);
                 PushTrackerStack(tracker);
             }
         }
@@ -802,15 +803,18 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
 
         private class TagBlockTracker
         {
-            public TagBlockTracker(string tagName, bool isTagHelper)
+            public TagBlockTracker(string tagName, bool isTagHelper, int depth)
             {
                 TagName = tagName;
                 IsTagHelper = isTagHelper;
+                Depth = depth;
             }
 
             public string TagName { get; }
 
             public bool IsTagHelper { get; }
+
+            public int Depth { get; }
         }
 
         private class TagHelperBlockTracker : TagBlockTracker
@@ -818,7 +822,7 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
             private IEnumerable<string> _prefixedAllowedChildren;
 
             public TagHelperBlockTracker(TagHelperBlockBuilder builder)
-                : base(builder.TagName, isTagHelper: true)
+                : base(builder.TagName, isTagHelper: true, depth: 0)
             {
                 Builder = builder;
 
diff --git a/test/Microsoft.AspNetCore.Razor.Test/Parser/TagHelpers/Internal/TagHelperParseTreeRewriterTest.cs b/test/Microsoft.AspNetCore.Razor.Test/Parser/TagHelpers/Internal/TagHelperParseTreeRewriterTest.cs
index 34e0135a1e..6b0bf074fb 100644
--- a/test/Microsoft.AspNetCore.Razor.Test/Parser/TagHelpers/Internal/TagHelperParseTreeRewriterTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Test/Parser/TagHelpers/Internal/TagHelperParseTreeRewriterTest.cs
@@ -4486,5 +4486,32 @@ namespace Microsoft.AspNetCore.Razor.Parser.TagHelpers.Internal
         {
             RunParseTreeRewriterTest(documentContent, expectedOutput, "p", "div");
         }
+
+        [Fact]
+        public void Rewrite_HandlesMalformedNestedNonTagHelperTags_Correctly()
+        {
+            var documentContent = "<div>@{</div>}";
+            var expectedOutput = new MarkupBlock(
+                new MarkupTagBlock(
+                    Factory.Markup("<div>")),
+                new StatementBlock(
+                    Factory.CodeTransition(),
+                    Factory.MetaCode("{").Accepts(AcceptedCharacters.None),
+                        new MarkupBlock(
+                            new MarkupTagBlock(
+                                Factory.Markup("</div>").Accepts(AcceptedCharacters.None))),
+                    Factory.EmptyCSharp().AsStatement(),
+                    Factory.MetaCode("}").Accepts(AcceptedCharacters.None)),
+                Factory.EmptyHtml());
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    "Encountered end tag \"div\" with no matching start tag.  Are your start/end tags properly balanced?",
+                    new SourceLocation(9, 0, 9),
+                    3),
+            };
+
+            RunParseTreeRewriterTest(documentContent, expectedOutput, expectedErrors);
+        }
     }
 }
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