From 41b7d90ea8bf4e633c2e24542e55424a8ab80072 Mon Sep 17 00:00:00 2001
From: Artak Mkrtchyan <artakm@corp.microsoft.com>
Date: Mon, 12 Feb 2018 22:03:53 -0800
Subject: [PATCH] Ignoring markup comments during validation

---
 .../Legacy/TagHelperParseTreeRewriter.cs              |  7 ++++++-
 .../Legacy/TagHelperParseTreeRewriterTest.cs          | 11 +++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs b/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
index 79b013f32d..73b545dd33 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
@@ -116,7 +116,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         continue;
                     }
                 }
-                else
+                else if (!IsCommentTag((Span)child))
                 {
                     ValidateParentAllowsContent((Span)child, errorSink);
                 }
@@ -817,6 +817,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             return relevantSymbol.Type == HtmlSymbolType.ForwardSlash;
         }
 
+        private static bool IsCommentTag(Span span)
+        {
+            return span.Content.StartsWith("<!--");
+        }
+
         private static void EnsureTagBlock(Block tagBlock)
         {
             Debug.Assert(tagBlock.Type == BlockKindInternal.Tag);
diff --git a/test/Microsoft.AspNetCore.Razor.Language.Test/Legacy/TagHelperParseTreeRewriterTest.cs b/test/Microsoft.AspNetCore.Razor.Language.Test/Legacy/TagHelperParseTreeRewriterTest.cs
index 04892592dd..bf0ae602db 100644
--- a/test/Microsoft.AspNetCore.Razor.Language.Test/Legacy/TagHelperParseTreeRewriterTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Language.Test/Legacy/TagHelperParseTreeRewriterTest.cs
@@ -1113,9 +1113,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         {
             // Arrangestring documentContent,
             IEnumerable<string> allowedChildren = new List<string> { "b" };
-            string literalPrefix = "";
+            string literal = "asdf";
             string commentOutput = $"<!--Hello World-->";
-            string expectedOutput = $"<p>{literalPrefix}{commentOutput}<b>asdf</b></p>";
+            string expectedOutput = $"<p><b>{literal}</b>{commentOutput}</p>";
 
             var pTagHelperBuilder = TagHelperDescriptorBuilder
                 .Create("PTagHelper", "SomeAssembly")
@@ -1127,7 +1127,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             var descriptors = new TagHelperDescriptor[]
             {
-                    pTagHelperBuilder.Build()
+                pTagHelperBuilder.Build()
             };
 
             var factory = new SpanFactory();
@@ -1135,7 +1135,10 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             var expectedMarkup = new MarkupBlock(
                 new MarkupTagHelperBlock("p",
-                    factory.Markup($"{literalPrefix}{commentOutput}")));
+                    blockFactory.MarkupTagBlock("<b>"),
+                    factory.Markup(literal),
+                    blockFactory.MarkupTagBlock("</b>"),
+                    factory.Markup(commentOutput)));
 
             // Act & Assert
             EvaluateData(