From 0c8dddcc40e1f0d9856ca380afd263a2d7f0308f Mon Sep 17 00:00:00 2001
From: Artak Mkrtchyan <artakm@corp.microsoft.com>
Date: Thu, 22 Feb 2018 17:05:13 -0800
Subject: [PATCH] Added the AllowHtmlCommentsInTagHelpers feature flag to
 control behavior of having comments in TagHelpers

---
 .../Legacy/TagHelperParseTreeRewriter.cs              |  8 +++++++-
 .../RazorParserFeatureFlags.cs                        | 11 +++++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs b/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
index 6cac8b46ea..a4c9906b1a 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperParseTreeRewriter.cs
@@ -488,7 +488,13 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         private void ValidateParentAllowsContent(Span child, ErrorSink errorSink)
         {
-            if (HasAllowedChildren() && !IsComment(child) && child.Kind != SpanKindInternal.Transition && child.Kind != SpanKindInternal.Code)
+            var isDisallowedContent = true;
+            if (_featureFlags.AllowHtmlCommentsInTagHelpers)
+            {
+                isDisallowedContent = !IsComment(child) && child.Kind != SpanKindInternal.Transition && child.Kind != SpanKindInternal.Code;
+            }
+
+            if (HasAllowedChildren() && isDisallowedContent)
             {
                 var content = child.Content;
                 if (!string.IsNullOrWhiteSpace(content))
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
index 0629eb9af8..409718b640 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
@@ -8,26 +8,33 @@ namespace Microsoft.AspNetCore.Razor.Language
         public static RazorParserFeatureFlags Create(RazorLanguageVersion version)
         {
             var allowMinimizedBooleanTagHelperAttributes = false;
+            var allowHtmlCommentsInTagHelpers = false;
 
             if (version.CompareTo(RazorLanguageVersion.Version_2_1) >= 0)
             {
                 // Added in 2.1
                 allowMinimizedBooleanTagHelperAttributes = true;
+                allowHtmlCommentsInTagHelpers = true;
             }
 
-            return new DefaultRazorParserFeatureFlags(allowMinimizedBooleanTagHelperAttributes);
+            return new DefaultRazorParserFeatureFlags(allowMinimizedBooleanTagHelperAttributes, allowHtmlCommentsInTagHelpers);
         }
 
         public abstract bool AllowMinimizedBooleanTagHelperAttributes { get; }
 
+        public abstract bool AllowHtmlCommentsInTagHelpers { get; }
+
         private class DefaultRazorParserFeatureFlags : RazorParserFeatureFlags
         {
-            public DefaultRazorParserFeatureFlags(bool allowMinimizedBooleanTagHelperAttributes)
+            public DefaultRazorParserFeatureFlags(bool allowMinimizedBooleanTagHelperAttributes, bool allowHtmlCommentsInTagHelpers)
             {
                 AllowMinimizedBooleanTagHelperAttributes = allowMinimizedBooleanTagHelperAttributes;
+                AllowHtmlCommentsInTagHelpers = allowHtmlCommentsInTagHelpers;
             }
 
             public override bool AllowMinimizedBooleanTagHelperAttributes { get; }
+
+            public override bool AllowHtmlCommentsInTagHelpers { get; }
         }
     }
 }