Expose source start/end tags on TagHelperBlocks.

- This is to enable the DesignTime to understand TagHelperBlocks full source structure in order to auto format the document.

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlock.cs

@@ -32,6 +32,8 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             Attributes = new Dictionary<string, SyntaxTreeNode>(source.Attributes);
             _start = source.Start;
             SelfClosing = source.SelfClosing;
+            SourceStartTag = source.SourceStartTag;
+            SourceEndTag = source.SourceEndTag;
 
             source.Reset();
 
@@ -41,6 +43,18 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             }
         }
 
+        /// <summary>
+        /// Gets the unrewritten source start tag.
+        /// </summary>
+        /// <remarks>This is used by design time to properly format <see cref="TagHelperBlock"/>s.</remarks>
+        public Block SourceStartTag { get; }
+
+        /// <summary>
+        /// Gets the unrewritten source end tag.
+        /// </summary>
+        /// <remarks>This is used by design time to properly format <see cref="TagHelperBlock"/>s.</remarks>
+        public Block SourceEndTag { get; }
+
         /// <summary>
         /// Indicates whether or not the tag is self closing.
         /// </summary>
@@ -70,6 +84,18 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
         /// </summary>
         public string TagName { get; private set; }
 
+        public override int Length
+        {
+            get
+            {
+                var startTagLength = SourceStartTag?.Length ?? 0;
+                var childrenLength = base.Length;
+                var endTagLength = SourceEndTag?.Length ?? 0;
+
+                return startTagLength + childrenLength + endTagLength;
+            }
+        }
+
         /// <inheritdoc />
         public override string ToString()
         {
@@ -99,7 +125,8 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
         /// <inheritdoc />
         public override int GetHashCode()
         {
-            return HashCodeCombiner.Start()
+            return HashCodeCombiner
+                .Start()
                 .Add(TagName)
                 .Add(Attributes)
                 .Add(base.GetHashCode())

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlockBuilder.cs

@@ -74,6 +74,18 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             }
         }
 
+        /// <summary>
+        /// Gets or sets the unrewritten source start tag.
+        /// </summary>
+        /// <remarks>This is used by design time to properly format <see cref="TagHelperBlock"/>s.</remarks>
+        public Block SourceStartTag { get; set; }
+
+        /// <summary>
+        /// Gets or sets the unrewritten source end tag.
+        /// </summary>
+        /// <remarks>This is used by design time to properly format <see cref="TagHelperBlock"/>s.</remarks>
+        public Block SourceEndTag { get; set; }
+
         /// <summary>
         /// Gets a value indicating whether or not the tag in the Razor source was self-closing.
         /// </summary>

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlockRewriter.cs

@@ -17,7 +17,8 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
     {
         private static readonly string StringTypeName = typeof(string).FullName;
 
-        public static TagHelperBlockBuilder Rewrite(string tagName,
+        public static TagHelperBlockBuilder Rewrite(
+            string tagName,
             bool validStructure,
             Block tag,
             IEnumerable<TagHelperDescriptor> descriptors,

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperParseTreeRewriter.cs

@@ -121,12 +121,17 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
 
                 var validTagStructure = ValidTagStructure(tagName, tagBlock, context);
 
-                var builder = TagHelperBlockRewriter.Rewrite(tagName,
+                var builder = TagHelperBlockRewriter.Rewrite(
+                    tagName,
                     validTagStructure,
                     tagBlock,
                     descriptors,
                     context.ErrorSink);
 
+                // Track the original start tag so the editor knows where each piece of the TagHelperBlock lies 
+                // for formatting.
+                builder.SourceStartTag = tagBlock;
+
                 // Found a new tag helper block
                 TrackTagHelperBlock(builder);
 
@@ -134,7 +139,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                 // within the tag... complete it.
                 if (builder.SelfClosing)
                 {
-                    BuildCurrentlyTrackedTagHelperBlock();
+                    BuildCurrentlyTrackedTagHelperBlock(endTag: null);
                 }
             }
             else
@@ -149,14 +154,14 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                 {
                     ValidTagStructure(tagName, tagBlock, context);
 
-                    BuildCurrentlyTrackedTagHelperBlock();
+                    BuildCurrentlyTrackedTagHelperBlock(tagBlock);
                 }
                 else
                 {
                     // Current tag helper scope does not match the end tag. Attempt to recover the tag 
                     // helper by looking up the previous tag helper scopes for a matching tag. If we 
                     // can't recover it means there was no corresponding tag helper begin tag.
-                    if (TryRecoverTagHelper(tagName, context))
+                    if (TryRecoverTagHelper(tagName, tagBlock, context))
                     {
                         ValidTagStructure(tagName, tagBlock, context);
 
@@ -230,9 +235,11 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
             }
         }
 
-        private void BuildCurrentlyTrackedTagHelperBlock()
+        private void BuildCurrentlyTrackedTagHelperBlock(Block endTag)
         {
-            _tagStack.Pop();
+            // Track the original end tag so the editor knows where each piece of the TagHelperBlock lies 
+            // for formatting.
+            _tagStack.Pop().SourceEndTag = endTag;
 
             BuildCurrentlyTrackedBlock();
         }
@@ -268,7 +275,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
             TrackBlock(builder);
         }
 
-        private bool TryRecoverTagHelper(string tagName, RewritingContext context)
+        private bool TryRecoverTagHelper(string tagName, Block endTag, RewritingContext context)
         {
             var malformedTagHelperCount = 0;
 
@@ -289,7 +296,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                 BuildMalformedTagHelpers(malformedTagHelperCount, context);
 
                 // One final build, this is the build that completes our target tag helper block which is not malformed.
-                BuildCurrentlyTrackedTagHelperBlock();
+                BuildCurrentlyTrackedTagHelperBlock(endTag);
 
                 // We were able to recover
                 return true;
@@ -310,7 +317,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                     RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(
                         malformedTagHelper.TagName));
 
-                BuildCurrentlyTrackedTagHelperBlock();
+                BuildCurrentlyTrackedTagHelperBlock(endTag: null);
             }
         }