Moved TagHelper directive validation and parsing from TagHelperBinder to

CSharpCodeParser

src/Microsoft.AspNetCore.Razor.Language/DefaultRazorTagHelperBinderPhase.cs

@@ -10,11 +10,6 @@ namespace Microsoft.AspNetCore.Razor.Language
 {
     internal class DefaultRazorTagHelperBinderPhase : RazorEnginePhaseBase, IRazorTagHelperBinderPhase
     {
-        private static HashSet<char> InvalidNonWhitespaceNameCharacters = new HashSet<char>(new[]
-        {
-            '@', '!', '<', '/', '?', '[', '>', ']', '=', '"', '\'', '*'
-        });
-
         protected override void ExecuteCore(RazorCodeDocument codeDocument)
         {
             var syntaxTree = codeDocument.GetSyntaxTree();
@@ -31,7 +26,8 @@ namespace Microsoft.AspNetCore.Razor.Language
             //
             // The imports come logically before the main razor file and are in the order they
             // should be processed.
-            var visitor = new DirectiveVisitor();
+            var descriptors = feature.GetDescriptors();
+            var visitor = new DirectiveVisitor(descriptors);
             var imports = codeDocument.GetImportSyntaxTrees();
             if (imports != null)
             {
@@ -44,14 +40,8 @@ namespace Microsoft.AspNetCore.Razor.Language
 
             visitor.VisitBlock(syntaxTree.Root);
 
-            var errorList = new List<RazorDiagnostic>();
+            var tagHelperPrefix = visitor.TagHelperPrefix;
-            var descriptors = feature.GetDescriptors();
+            descriptors = visitor.Matches.ToArray();
-
-            var directives = visitor.Directives;
-            descriptors = ProcessDirectives(directives, descriptors);
-
-            var tagHelperPrefix = ProcessTagHelperPrefix(directives, codeDocument);
-            var root = syntaxTree.Root;
 
             var context = TagHelperDocumentContext.Create(tagHelperPrefix, descriptors);
             codeDocument.SetTagHelperContext(context);
@@ -64,9 +54,11 @@ namespace Microsoft.AspNetCore.Razor.Language
 
             var errorSink = new ErrorSink();
             var rewriter = new TagHelperParseTreeRewriter(tagHelperPrefix, descriptors);
+            var root = syntaxTree.Root;
             root = rewriter.Rewrite(root, errorSink);
 
             // Temporary code while we're still using legacy diagnostics in the SyntaxTree.
+            var errorList = new List<RazorDiagnostic>();
             errorList.AddRange(errorSink.Errors.Select(error => RazorDiagnostic.Create(error)));
 
             errorList.AddRange(descriptors.SelectMany(d => d.GetAllDiagnostics()));
@@ -77,205 +69,27 @@ namespace Microsoft.AspNetCore.Razor.Language
             codeDocument.SetSyntaxTree(newSyntaxTree);
         }
 
-        // Internal for testing
+        private static bool MatchesDirective(TagHelperDescriptor descriptor, string typePattern, string assemblyName)
-        internal string ProcessTagHelperPrefix(List<TagHelperDirectiveDescriptor> directives, RazorCodeDocument codeDocument)
         {
-            // We only support a single prefix directive.
+            if (!string.Equals(descriptor.AssemblyName, assemblyName, StringComparison.Ordinal))
-            TagHelperDirectiveDescriptor prefixDirective = null;
-            for (var i = 0; i < directives.Count; i++)
-            {
-                if (directives[i].DirectiveType == TagHelperDirectiveType.TagHelperPrefix)
-                {
-                    // We only expect to see a single one of these per file, but that's enforced at another level.
-                    prefixDirective = directives[i];
-                }
-            }
-
-            var prefix = prefixDirective?.DirectiveText;
-            if (prefix != null && !IsValidTagHelperPrefix(prefix, prefixDirective.Location, prefixDirective.Diagnostics))
-            {
-                prefix = null;
-            }
-
-            if (!string.IsNullOrEmpty(prefix))
-            {
-                return prefixDirective.DirectiveText;
-            }
-
-            return null;
-        }
-
-        internal IReadOnlyList<TagHelperDescriptor> ProcessDirectives(
-            IReadOnlyList<TagHelperDirectiveDescriptor> directives,
-            IReadOnlyList<TagHelperDescriptor> tagHelpers)
-        {
-            var matches = new HashSet<TagHelperDescriptor>(TagHelperDescriptorComparer.Default);
-
-            for (var i = 0; i < directives.Count; i++)
-            {
-                var directive = directives[i];
-
-                ParsedDirective parsed;
-                switch (directive.DirectiveType)
-                {
-                    case TagHelperDirectiveType.AddTagHelper:
-
-                        parsed = ParseAddOrRemoveDirective(directive);
-                        if (parsed == null)
-                        {
-                            // Skip this one, it's an error
-                            break;
-                        }
-
-                        if (!AssemblyContainsTagHelpers(parsed.AssemblyName, tagHelpers))
-                        {
-                            // No tag helpers in the assembly.
-                            break;
-                        }
-
-                        for (var j = 0; j < tagHelpers.Count; j++)
-                        {
-                            var tagHelper = tagHelpers[j];
-                            if (MatchesDirective(tagHelper, parsed))
-                            {
-                                matches.Add(tagHelper);
-                            }
-                        }
-
-                        break;
-
-                    case TagHelperDirectiveType.RemoveTagHelper:
-
-                        parsed = ParseAddOrRemoveDirective(directive);
-                        if (parsed == null)
-                        {
-                            // Skip this one, it's an error
-                            break;
-                        }
-
-
-                        if (!AssemblyContainsTagHelpers(parsed.AssemblyName, tagHelpers))
-                        {
-                            // No tag helpers in the assembly.
-                            break;
-                        }
-
-                        for (var j = 0; j < tagHelpers.Count; j++)
-                        {
-                            var tagHelper = tagHelpers[j];
-                            if (MatchesDirective(tagHelper, parsed))
-                            {
-                                matches.Remove(tagHelper);
-                            }
-                        }
-
-                        break;
-                }
-            }
-
-            return matches.ToArray();
-        }
-
-        private bool AssemblyContainsTagHelpers(string assemblyName, IReadOnlyList<TagHelperDescriptor> tagHelpers)
-        {
-            for (var i = 0; i < tagHelpers.Count; i++)
-            {
-                if (string.Equals(tagHelpers[i].AssemblyName, assemblyName, StringComparison.Ordinal))
-                {
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
-        // Internal for testing
-        internal ParsedDirective ParseAddOrRemoveDirective(TagHelperDirectiveDescriptor directive)
-        {
-            var text = directive.DirectiveText;
-            var lookupStrings = text?.Split(new[] { ',' });
-
-            // Ensure that we have valid lookupStrings to work with. The valid format is "typeName, assemblyName"
-            if (lookupStrings == null ||
-                lookupStrings.Any(string.IsNullOrWhiteSpace) ||
-                lookupStrings.Length != 2)
-            {
-                directive.Diagnostics.Add(
-                    RazorDiagnostic.Create(
-                        new RazorError(
-                            Resources.FormatInvalidTagHelperLookupText(text),
-                            directive.Location,
-                            Math.Max(text.Length, 1))));
-
-                return null;
-            }
-
-            var trimmedAssemblyName = lookupStrings[1].Trim();
-
-            // + 1 is for the comma separator in the lookup text.
-            var assemblyNameIndex =
-                lookupStrings[0].Length + 1 + lookupStrings[1].IndexOf(trimmedAssemblyName, StringComparison.Ordinal);
-            var assemblyNamePrefix = directive.DirectiveText.Substring(0, assemblyNameIndex);
-            var assemblyNameLocation = new SourceLocation(
-                directive.Location.FilePath,
-                directive.Location.AbsoluteIndex + assemblyNameIndex,
-                directive.Location.LineIndex,
-                directive.Location.CharacterIndex + assemblyNameIndex);
-
-            return new ParsedDirective
-            {
-                TypePattern = lookupStrings[0].Trim(),
-                AssemblyName = trimmedAssemblyName,
-                AssemblyNameLocation = assemblyNameLocation,
-            };
-        }
-
-        // Internal for testing
-        internal bool IsValidTagHelperPrefix(
-            string prefix,
-            SourceLocation directiveLocation,
-            List<RazorDiagnostic> diagnostics)
-        {
-            foreach (var character in prefix)
-            {
-                // Prefixes are correlated with tag names, tag names cannot have whitespace.
-                if (char.IsWhiteSpace(character) ||  InvalidNonWhitespaceNameCharacters.Contains(character))
-                {
-                    diagnostics.Add(
-                        RazorDiagnostic.Create(
-                            new RazorError(
-                                Resources.FormatInvalidTagHelperPrefixValue(SyntaxConstants.CSharp.TagHelperPrefixKeyword, character, prefix),
-                                directiveLocation,
-                                prefix.Length)));
-
-                    return false;
-                }
-            }
-
-            return true;
-        }
-
-        private static bool MatchesDirective(TagHelperDescriptor descriptor, ParsedDirective lookupInfo)
-        {
-            if (!string.Equals(descriptor.AssemblyName, lookupInfo.AssemblyName, StringComparison.Ordinal))
             {
                 return false;
             }
 
-            if (lookupInfo.TypePattern.EndsWith("*", StringComparison.Ordinal))
+            if (typePattern.EndsWith("*", StringComparison.Ordinal))
             {
-                if (lookupInfo.TypePattern.Length == 1)
+                if (typePattern.Length == 1)
                 {
                     // TypePattern is "*".
                     return true;
                 }
 
-                var lookupTypeName = lookupInfo.TypePattern.Substring(0, lookupInfo.TypePattern.Length - 1);
+                var lookupTypeName = typePattern.Substring(0, typePattern.Length - 1);
 
                 return descriptor.Name.StartsWith(lookupTypeName, StringComparison.Ordinal);
             }
 
-            return string.Equals(descriptor.Name, lookupInfo.TypePattern, StringComparison.Ordinal);
+            return string.Equals(descriptor.Name, typePattern, StringComparison.Ordinal);
         }
 
         private static int GetErrorLength(string directiveText)
@@ -295,81 +109,89 @@ namespace Microsoft.AspNetCore.Razor.Language
             return combinedErrors;
         }
 
-        internal class ParsedDirective
+        // Internal for testing.
+        internal class DirectiveVisitor : ParserVisitor
         {
-            public string AssemblyName { get; set; }
+            private IReadOnlyList<TagHelperDescriptor> _tagHelpers;
 
-            public string TypePattern { get; set; }
+            public DirectiveVisitor(IReadOnlyList<TagHelperDescriptor> tagHelpers)
+            {
+                _tagHelpers = tagHelpers;
+            }
 
-            public SourceLocation AssemblyNameLocation { get; set; }
+            public string TagHelperPrefix { get; private set; }
-        }
 
-        private class DirectiveVisitor : ParserVisitor
+            public HashSet<TagHelperDescriptor> Matches { get; } = new HashSet<TagHelperDescriptor>();
-        {
-            public List<TagHelperDirectiveDescriptor> Directives { get; } = new List<TagHelperDirectiveDescriptor>();
 
             public override void VisitAddTagHelperSpan(AddTagHelperChunkGenerator chunkGenerator, Span span)
             {
-                var directive = CreateDirective(span, chunkGenerator.LookupText, TagHelperDirectiveType.AddTagHelper, chunkGenerator.Diagnostics);
+                if (chunkGenerator.AssemblyName == null)
-                Directives.Add(directive);
+                {
+                    // Skip this one, it's an error
+                    return;
+                }
+
+                if (!AssemblyContainsTagHelpers(chunkGenerator.AssemblyName, _tagHelpers))
+                {
+                    // No tag helpers in the assembly.
+                    return;
+                }
+
+                for (var i = 0; i < _tagHelpers.Count; i++)
+                {
+                    var tagHelper = _tagHelpers[i];
+                    if (MatchesDirective(tagHelper, chunkGenerator.TypePattern, chunkGenerator.AssemblyName))
+                    {
+                        Matches.Add(tagHelper);
+                    }
+                }
             }
 
             public override void VisitRemoveTagHelperSpan(RemoveTagHelperChunkGenerator chunkGenerator, Span span)
             {
-                var directive = CreateDirective(span, chunkGenerator.LookupText, TagHelperDirectiveType.RemoveTagHelper, chunkGenerator.Diagnostics);
+                if (chunkGenerator.AssemblyName == null)
-                Directives.Add(directive);
+                {
+                    // Skip this one, it's an error
+                    return;
+                }
+
+
+                if (!AssemblyContainsTagHelpers(chunkGenerator.AssemblyName, _tagHelpers))
+                {
+                    // No tag helpers in the assembly.
+                    return;
+                }
+
+                for (var i = 0; i < _tagHelpers.Count; i++)
+                {
+                    var tagHelper = _tagHelpers[i];
+                    if (MatchesDirective(tagHelper, chunkGenerator.TypePattern, chunkGenerator.AssemblyName))
+                    {
+                        Matches.Remove(tagHelper);
+                    }
+                }
             }
 
             public override void VisitTagHelperPrefixDirectiveSpan(TagHelperPrefixDirectiveChunkGenerator chunkGenerator, Span span)
             {
-                var directive = CreateDirective(span, chunkGenerator.Prefix, TagHelperDirectiveType.TagHelperPrefix, chunkGenerator.Diagnostics);
+                if (!string.IsNullOrEmpty(chunkGenerator.DirectiveText))
-                Directives.Add(directive);
+                {
+                    // We only expect to see a single one of these per file, but that's enforced at another level.
+                    TagHelperPrefix = chunkGenerator.DirectiveText;
+                }
             }
 
-            private TagHelperDirectiveDescriptor CreateDirective(
+            private bool AssemblyContainsTagHelpers(string assemblyName, IReadOnlyList<TagHelperDescriptor> tagHelpers)
-                Span span,
-                string directiveText,
-                TagHelperDirectiveType directiveType,
-                List<RazorDiagnostic> diagnostics)
             {
-                directiveText = directiveText.Trim();
+                for (var i = 0; i < tagHelpers.Count; i++)
-                if (directiveText.Length >= 2 &&
-                    directiveText.StartsWith("\"", StringComparison.Ordinal) &&
-                    directiveText.EndsWith("\"", StringComparison.Ordinal))
                 {
-                    directiveText = directiveText.Substring(1, directiveText.Length - 2);
+                    if (string.Equals(tagHelpers[i].AssemblyName, assemblyName, StringComparison.Ordinal))
+                    {
+                        return true;
+                    }
                 }
 
-                // If this is the "string literal" form of a directive, we'll need to postprocess the location
+                return false;
-                // and content.
-                //
-                // Ex: @addTagHelper "*, Microsoft.AspNetCore.CoolLibrary"
-                //                    ^                                 ^
-                //                  Start                              End
-                var directiveStart = span.Start;
-                if (span.Symbols.Count == 1 && (span.Symbols[0] as CSharpSymbol)?.Type == CSharpSymbolType.StringLiteral)
-                {
-                    var offset = span.Content.IndexOf(directiveText, StringComparison.Ordinal);
-
-                    // This is safe because inside one of these directives all of the text needs to be on the
-                    // same line.
-                    var original = span.Start;
-                    directiveStart = new SourceLocation(
-                        original.FilePath,
-                        original.AbsoluteIndex + offset,
-                        original.LineIndex,
-                        original.CharacterIndex + offset);
-                }
-
-                var directiveDescriptor = new TagHelperDirectiveDescriptor
-                {
-                    DirectiveText = directiveText,
-                    Location = directiveStart,
-                    DirectiveType = directiveType,
-                    Diagnostics = diagnostics,
-                };
-
-                return directiveDescriptor;
             }
         }
     }

src/Microsoft.AspNetCore.Razor.Language/Legacy/AddTagHelperChunkGenerator.cs

@@ -10,14 +10,28 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class AddTagHelperChunkGenerator : SpanChunkGenerator
     {
-        public AddTagHelperChunkGenerator(string lookupText, List<RazorDiagnostic> diagnostics)
+        public AddTagHelperChunkGenerator(
+            string lookupText,
+            string directiveText,
+            string typePattern,
+            string assemblyName,
+            List<RazorDiagnostic> diagnostics)
         {
             LookupText = lookupText;
+            DirectiveText = directiveText;
+            AssemblyName = assemblyName;
+            TypePattern = typePattern;
             Diagnostics = diagnostics;
         }
 
         public string LookupText { get; }
 
+        public string DirectiveText { get; set; }
+
+        public string TypePattern { get; set; }
+
+        public string AssemblyName { get; set; }
+
         public List<RazorDiagnostic> Diagnostics { get; }
 
         public override void Accept(ParserVisitor visitor, Span span)
@@ -31,7 +45,10 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var other = obj as AddTagHelperChunkGenerator;
             return base.Equals(other) &&
                 Enumerable.SequenceEqual(Diagnostics, other.Diagnostics) &&
-                string.Equals(LookupText, other.LookupText, StringComparison.Ordinal);
+                string.Equals(LookupText, other.LookupText, StringComparison.Ordinal) &&
+                string.Equals(DirectiveText, other.DirectiveText, StringComparison.Ordinal) &&
+                string.Equals(TypePattern, other.TypePattern, StringComparison.Ordinal) &&
+                string.Equals(AssemblyName, other.AssemblyName, StringComparison.Ordinal);
         }
 
         /// <inheritdoc />
@@ -40,6 +57,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var combiner = HashCodeCombiner.Start();
             combiner.Add(base.GetHashCode());
             combiner.Add(LookupText, StringComparer.Ordinal);
+            combiner.Add(DirectiveText, StringComparer.Ordinal);
+            combiner.Add(TypePattern, StringComparer.Ordinal);
+            combiner.Add(AssemblyName, StringComparer.Ordinal);
 
             return combiner.CombinedHash;
         }

src/Microsoft.AspNetCore.Razor.Language/Legacy/CSharpCodeParser.cs

@@ -10,6 +10,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class CSharpCodeParser : TokenizerBackedParser<CSharpTokenizer, CSharpSymbol, CSharpSymbolType>
     {
+        private static HashSet<char> InvalidNonWhitespaceNameCharacters = new HashSet<char>(new[]
+        {
+            '@', '!', '<', '/', '?', '[', '>', ']', '=', '"', '\'', '*'
+        });
+
         private static readonly Func<CSharpSymbol, bool> IsValidStatementSpacingSymbol =
             IsSpacingToken(includeNewLines: true, includeComments: true);
 
@@ -1905,22 +1910,158 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         errors.Add(duplicateDiagnostic);
                     }
 
-                    return new TagHelperPrefixDirectiveChunkGenerator(prefix, errors);
+                    var parsedDirective = ParseDirective(prefix, Span.Start, TagHelperDirectiveType.TagHelperPrefix, errors);
+
+                    return new TagHelperPrefixDirectiveChunkGenerator(
+                        prefix,
+                        parsedDirective.DirectiveText,
+                        errors);
                 });
         }
 
+        // Internal for testing.
+        internal void ValidateTagHelperPrefix(
+            string prefix,
+            SourceLocation directiveLocation,
+            List<RazorDiagnostic> diagnostics)
+        {
+            foreach (var character in prefix)
+            {
+                // Prefixes are correlated with tag names, tag names cannot have whitespace.
+                if (char.IsWhiteSpace(character) || InvalidNonWhitespaceNameCharacters.Contains(character))
+                {
+                    diagnostics.Add(
+                        RazorDiagnostic.Create(
+                            new RazorError(
+                                Resources.FormatInvalidTagHelperPrefixValue(SyntaxConstants.CSharp.TagHelperPrefixKeyword, character, prefix),
+                                directiveLocation,
+                                prefix.Length)));
+
+                    return;
+                }
+            }
+        }
+
+        private ParsedDirective ParseDirective(
+            string directiveText,
+            SourceLocation directiveLocation,
+            TagHelperDirectiveType directiveType,
+            List<RazorDiagnostic> errors)
+        {
+            var offset = 0;
+            directiveText = directiveText.Trim();
+            if (directiveText.Length >= 2 &&
+                directiveText.StartsWith("\"", StringComparison.Ordinal) &&
+                directiveText.EndsWith("\"", StringComparison.Ordinal))
+            {
+                directiveText = directiveText.Substring(1, directiveText.Length - 2);
+                if (string.IsNullOrEmpty(directiveText))
+                {
+                    offset = 1;
+                }
+            }
+
+            // If this is the "string literal" form of a directive, we'll need to postprocess the location
+            // and content.
+            //
+            // Ex: @addTagHelper "*, Microsoft.AspNetCore.CoolLibrary"
+            //                    ^                                 ^
+            //                  Start                              End
+            if (Span.Symbols.Count == 1 && (Span.Symbols[0] as CSharpSymbol)?.Type == CSharpSymbolType.StringLiteral)
+            {
+                offset += Span.Symbols[0].Content.IndexOf(directiveText, StringComparison.Ordinal);
+
+                // This is safe because inside one of these directives all of the text needs to be on the
+                // same line.
+                var original = directiveLocation;
+                directiveLocation = new SourceLocation(
+                    original.FilePath,
+                    original.AbsoluteIndex + offset,
+                    original.LineIndex,
+                    original.CharacterIndex + offset);
+            }
+
+            var parsedDirective = new ParsedDirective()
+            {
+                DirectiveText = directiveText
+            };
+
+            if (directiveType == TagHelperDirectiveType.TagHelperPrefix)
+            {
+                ValidateTagHelperPrefix(parsedDirective.DirectiveText, directiveLocation, errors);
+
+                return parsedDirective;
+            }
+
+            return ParseAddOrRemoveDirective(parsedDirective, directiveLocation, errors);
+        }
+
+        // Internal for testing.
+        internal ParsedDirective ParseAddOrRemoveDirective(ParsedDirective directive, SourceLocation directiveLocation, List<RazorDiagnostic> errors)
+        {
+            var text = directive.DirectiveText;
+            var lookupStrings = text?.Split(new[] { ',' });
+
+            // Ensure that we have valid lookupStrings to work with. The valid format is "typeName, assemblyName"
+            if (lookupStrings == null ||
+                lookupStrings.Any(string.IsNullOrWhiteSpace) ||
+                lookupStrings.Length != 2)
+            {
+                errors.Add(
+                    RazorDiagnostic.Create(
+                        new RazorError(
+                            Resources.FormatInvalidTagHelperLookupText(text),
+                            directiveLocation,
+                            Math.Max(text.Length, 1))));
+
+                return directive;
+            }
+
+            var trimmedAssemblyName = lookupStrings[1].Trim();
+
+            // + 1 is for the comma separator in the lookup text.
+            var assemblyNameIndex =
+                lookupStrings[0].Length + 1 + lookupStrings[1].IndexOf(trimmedAssemblyName, StringComparison.Ordinal);
+            var assemblyNamePrefix = directive.DirectiveText.Substring(0, assemblyNameIndex);
+
+            directive.TypePattern = lookupStrings[0].Trim();
+            directive.AssemblyName = trimmedAssemblyName;
+
+            return directive;
+        }
+
         protected virtual void AddTagHelperDirective()
         {
             TagHelperDirective(
                 SyntaxConstants.CSharp.AddTagHelperKeyword,
-                (lookupText, errors) => new AddTagHelperChunkGenerator(lookupText, errors));
+                (lookupText, errors) =>
+                {
+                    var parsedDirective = ParseDirective(lookupText, Span.Start, TagHelperDirectiveType.AddTagHelper, errors);
+
+                    return new AddTagHelperChunkGenerator(
+                        lookupText,
+                        parsedDirective.DirectiveText,
+                        parsedDirective.TypePattern,
+                        parsedDirective.AssemblyName,
+                        errors);
+                });
         }
 
         protected virtual void RemoveTagHelperDirective()
         {
             TagHelperDirective(
                 SyntaxConstants.CSharp.RemoveTagHelperKeyword,
-                (lookupText, errors) => new RemoveTagHelperChunkGenerator(lookupText, errors));
+                (lookupText, errors) =>
+                {
+                    var parsedDirective = ParseDirective(lookupText, Span.Start, TagHelperDirectiveType.RemoveTagHelper, errors);
+
+                    return new RemoveTagHelperChunkGenerator(
+                        lookupText,
+                        parsedDirective.DirectiveText,
+                        parsedDirective.TypePattern,
+                        parsedDirective.AssemblyName,
+                        errors);
+                });
         }
 
         [Conditional("DEBUG")]
@@ -2093,5 +2234,14 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                 return sym.Content;
             }
         }
+
+        internal class ParsedDirective
+        {
+            public string DirectiveText { get; set; }
+
+            public string AssemblyName { get; set; }
+
+            public string TypePattern { get; set; }
+        }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/Legacy/RemoveTagHelperChunkGenerator.cs

@@ -10,14 +10,28 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class RemoveTagHelperChunkGenerator : SpanChunkGenerator
     {
-        public RemoveTagHelperChunkGenerator(string lookupText, List<RazorDiagnostic> diagnostics)
+        public RemoveTagHelperChunkGenerator(
+            string lookupText,
+            string directiveText,
+            string typePattern,
+            string assemblyName,
+            List<RazorDiagnostic> diagnostics)
         {
             LookupText = lookupText;
+            DirectiveText = directiveText;
+            TypePattern = typePattern;
+            AssemblyName = assemblyName;
             Diagnostics = diagnostics;
         }
 
         public string LookupText { get; }
 
+        public string DirectiveText { get; set; }
+
+        public string TypePattern { get; set; }
+
+        public string AssemblyName { get; set; }
+
         public List<RazorDiagnostic> Diagnostics { get; }
 
         public override void Accept(ParserVisitor visitor, Span span)
@@ -31,7 +45,10 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var other = obj as RemoveTagHelperChunkGenerator;
             return base.Equals(other) &&
                 Enumerable.SequenceEqual(Diagnostics, other.Diagnostics) &&
-                string.Equals(LookupText, other.LookupText, StringComparison.Ordinal);
+                string.Equals(LookupText, other.LookupText, StringComparison.Ordinal) &&
+                string.Equals(DirectiveText, other.DirectiveText, StringComparison.Ordinal) &&
+                string.Equals(TypePattern, other.TypePattern, StringComparison.Ordinal) &&
+                string.Equals(AssemblyName, other.AssemblyName, StringComparison.Ordinal);
         }
 
         /// <inheritdoc />
@@ -40,6 +57,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var combiner = HashCodeCombiner.Start();
             combiner.Add(base.GetHashCode());
             combiner.Add(LookupText, StringComparer.Ordinal);
+            combiner.Add(DirectiveText, StringComparer.Ordinal);
+            combiner.Add(TypePattern, StringComparer.Ordinal);
+            combiner.Add(AssemblyName, StringComparer.Ordinal);
 
             return combiner.CombinedHash;
         }

src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperDirectiveDescriptor.cs

@@ -1,48 +0,0 @@
-// 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 System;
-using System.Collections.Generic;
-
-namespace Microsoft.AspNetCore.Razor.Language.Legacy
-{
-    /// <summary>
-    /// Contains information needed to resolve <see cref="TagHelperDescriptor"/>s.
-    /// </summary>
-    internal class TagHelperDirectiveDescriptor
-    {
-        private string _directiveText;
-
-        /// <summary>
-        /// A <see cref="string"/> used to find tag helper <see cref="System.Type"/>s.
-        /// </summary>
-        public string DirectiveText
-        {
-            get
-            {
-                return _directiveText;
-            }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException(nameof(value));
-                }
-
-                _directiveText = value;
-            }
-        }
-
-        /// <summary>
-        /// The <see cref="SourceLocation"/> of the directive.
-        /// </summary>
-        public SourceLocation Location { get; set; } = SourceLocation.Zero;
-
-        /// <summary>
-        /// The <see cref="TagHelperDirectiveType"/> of this directive.
-        /// </summary>
-        public TagHelperDirectiveType DirectiveType { get; set; }
-
-        public List<RazorDiagnostic> Diagnostics { get; set; }
-    }
-}

src/Microsoft.AspNetCore.Razor.Language/Legacy/TagHelperPrefixDirectiveChunkGenerator.cs

@@ -10,14 +10,17 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class TagHelperPrefixDirectiveChunkGenerator : SpanChunkGenerator
     {
-        public TagHelperPrefixDirectiveChunkGenerator(string prefix, List<RazorDiagnostic> diagnostics)
+        public TagHelperPrefixDirectiveChunkGenerator(string prefix, string directiveText, List<RazorDiagnostic> diagnostics)
         {
             Prefix = prefix;
+            DirectiveText = directiveText;
             Diagnostics = diagnostics;
         }
 
         public string Prefix { get; }
 
+        public string DirectiveText { get; }
+
         public List<RazorDiagnostic> Diagnostics { get; }
 
         public override void Accept(ParserVisitor visitor, Span span)
@@ -31,7 +34,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var other = obj as TagHelperPrefixDirectiveChunkGenerator;
             return base.Equals(other) &&
                 Enumerable.SequenceEqual(Diagnostics, other.Diagnostics) &&
-                string.Equals(Prefix, other.Prefix, StringComparison.Ordinal);
+                string.Equals(Prefix, other.Prefix, StringComparison.Ordinal) &&
+                string.Equals(DirectiveText, other.DirectiveText, StringComparison.Ordinal);
         }
 
         /// <inheritdoc />
@@ -40,6 +44,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var combiner = HashCodeCombiner.Start();
             combiner.Add(base.GetHashCode());
             combiner.Add(Prefix, StringComparer.Ordinal);
+            combiner.Add(DirectiveText, StringComparer.Ordinal);
 
             return combiner.CombinedHash;
         }

test/Microsoft.AspNetCore.Razor.Language.Test/Legacy/CSharpDirectivesTest.cs

@@ -350,7 +350,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                             .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"*, Foo\"")
-                        .AsAddTagHelper("\"*, Foo\"")));
+                        .AsAddTagHelper(
+                            "\"*, Foo\"",
+                            "*, Foo",
+                            "*",
+                            "Foo")));
         }
 
         [Fact]
@@ -370,7 +374,10 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                                .Accepts(AcceptedCharactersInternal.None),
                         Factory.Code("\"*, Foo\"")
                             .AsAddTagHelper(
-                                "\"*, Foo\"", 
+                                "\"*, Foo\"",
+                                "*, Foo",
+                                "*",
+                                "Foo",
                                 new RazorError(Resources.FormatDirectiveMustAppearAtStartOfLine("addTagHelper"), new SourceLocation(4, 0, 4), 12))),
                     Factory.Code(Environment.NewLine).AsStatement(),
                     Factory.MetaCode("}").Accepts(AcceptedCharactersInternal.None)));
@@ -1009,7 +1016,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"\"")
-                        .AsTagHelperPrefixDirective("\"\"")));
+                        .AsTagHelperPrefixDirective("\"\"", string.Empty)));
         }
 
         [Fact]
@@ -1022,7 +1029,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo")
-                        .AsTagHelperPrefixDirective("Foo")));
+                        .AsTagHelperPrefixDirective("Foo", "Foo")));
         }
 
         [Fact]
@@ -1035,7 +1042,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo\"")
-                        .AsTagHelperPrefixDirective("\"Foo\"")));
+                        .AsTagHelperPrefixDirective("\"Foo\"", "Foo")));
         }
 
         [Fact]
@@ -1054,7 +1061,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.EmptyCSharp()
-                        .AsTagHelperPrefixDirective(string.Empty, expectedError)
+                        .AsTagHelperPrefixDirective(string.Empty, string.Empty, expectedError)
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
@@ -1069,6 +1076,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.TagHelperPrefixKeyword),
+                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperPrefixValue(SyntaxConstants.CSharp.TagHelperPrefixKeyword, '"', "\"Foo"),
                     absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4)
             };
 
@@ -1080,7 +1090,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo")
-                        .AsTagHelperPrefixDirective("\"Foo", expectedErrors)));
+                        .AsTagHelperPrefixDirective("\"Foo", "\"Foo", expectedErrors)));
         }
 
         [Fact]
@@ -1094,6 +1104,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 23, lineIndex: 0, columnIndex: 23, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.TagHelperPrefixKeyword),
+                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 7),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperPrefixValue(SyntaxConstants.CSharp.TagHelperPrefixKeyword, ' ', "Foo   \""),
                     absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 7)
             };
 
@@ -1105,43 +1118,76 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                         .MetaCode(SyntaxConstants.CSharp.TagHelperPrefixKeyword + " ")
                         .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo   \"")
-                        .AsTagHelperPrefixDirective("Foo   \"", expectedErrors)));
+                        .AsTagHelperPrefixDirective("Foo   \"", "Foo   \"", expectedErrors)));
         }
 
         [Fact]
-        public void RemoveTagHelperDirective_NoValue_Succeeds()
+        public void RemoveTagHelperDirective_NoValue_Invalid()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText(string.Empty),
+                    new SourceLocation(18, 0, 18),
+                    length: 1)
+            };
+
             ParseBlockTest("@removeTagHelper \"\"",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"\"")
-                        .AsRemoveTagHelper("\"\"")));
+                        .AsRemoveTagHelper(
+                            "\"\"",
+                            string.Empty,
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
-        public void RemoveTagHelperDirective_Succeeds()
+        public void RemoveTagHelperDirective_InvalidLookupText_AddsError()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo"),
+                    new SourceLocation(17, 0, 17),
+                    length: 3)
+            };
+
             ParseBlockTest("@removeTagHelper Foo",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo")
-                        .AsRemoveTagHelper("Foo")));
+                        .AsRemoveTagHelper(
+                            "Foo",
+                            "Foo",
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
-        public void RemoveTagHelperDirective_WithQuotes_Succeeds()
+        public void RemoveTagHelperDirective_WithQuotes_InvalidLookupText_AddsError()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo"),
+                    new SourceLocation(18, 0, 18),
+                    length: 3)
+            };
+
             ParseBlockTest("@removeTagHelper \"Foo\"",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo\"")
-                        .AsRemoveTagHelper("\"Foo\"")));
+                        .AsRemoveTagHelper(
+                            "\"Foo\"",
+                            "Foo",
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
@@ -1153,7 +1199,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + "     ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo,   Bar    ")
-                        .AsRemoveTagHelper("Foo,   Bar")
+                        .AsRemoveTagHelper(
+                            "Foo,   Bar",
+                            "Foo,   Bar",
+                            "Foo",
+                            "Bar")
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
@@ -1161,9 +1211,16 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         public void RemoveTagHelperDirective_RequiresValue()
         {
             // Arrange
-            var expectedError = new RazorError(
+            var expectedErrors = new[]
-                LegacyResources.FormatParseError_DirectiveMustHaveValue(SyntaxConstants.CSharp.RemoveTagHelperKeyword),
+            {
-                absoluteIndex: 1, lineIndex: 0, columnIndex: 1, length: 15);
+                new RazorError(
+                    LegacyResources.FormatParseError_DirectiveMustHaveValue(SyntaxConstants.CSharp.RemoveTagHelperKeyword),
+                    absoluteIndex: 1, lineIndex: 0, columnIndex: 1, length: 15),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText(string.Empty),
+                    new SourceLocation(17, 0, 17),
+                    length: 1),
+            };
 
             // Act & Assert
             ParseBlockTest("@removeTagHelper ",
@@ -1172,7 +1229,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.EmptyCSharp()
-                        .AsRemoveTagHelper(string.Empty, expectedError)
+                        .AsRemoveTagHelper(string.Empty, string.Empty, legacyErrors: expectedErrors)
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
@@ -1187,7 +1244,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.RemoveTagHelperKeyword),
-                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4)
+                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("\"Foo"),
+                    new SourceLocation(17, 0, 17),
+                    length: 4),
             };
 
             // Act & Assert
@@ -1197,7 +1258,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo")
-                        .AsRemoveTagHelper("\"Foo", expectedErrors)));
+                        .AsRemoveTagHelper("\"Foo", "\"Foo", legacyErrors: expectedErrors)));
         }
 
         [Fact]
@@ -1211,7 +1272,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 20, lineIndex: 0, columnIndex: 20, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.RemoveTagHelperKeyword),
-                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4)
+                    absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 4),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo\""),
+                    new SourceLocation(17, 0, 17),
+                    length: 4),
             };
 
             // Act & Assert
@@ -1221,48 +1286,81 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.RemoveTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo\"")
-                        .AsRemoveTagHelper("Foo\"", expectedErrors)
+                        .AsRemoveTagHelper("Foo\"", "Foo\"", legacyErrors: expectedErrors)
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
         [Fact]
-        public void AddTagHelperDirective_NoValue_Succeeds()
+        public void AddTagHelperDirective_NoValue_Invalid()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText(string.Empty),
+                    new SourceLocation(15, 0, 15),
+                    length: 1)
+            };
+
             ParseBlockTest("@addTagHelper \"\"",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"\"")
-                        .AsAddTagHelper("\"\"")));
+                        .AsAddTagHelper(
+                            "\"\"",
+                            string.Empty,
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
-        public void AddTagHelperDirective_Succeeds()
+        public void AddTagHelperDirective_InvalidLookupText_AddsError()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo"),
+                    new SourceLocation(14, 0, 14),
+                    length: 3)
+            };
+
             ParseBlockTest("@addTagHelper Foo",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo")
-                        .AsAddTagHelper("Foo")));
+                        .AsAddTagHelper(
+                            "Foo",
+                            "Foo",
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
-        public void AddTagHelperDirective_WithQuotes_Succeeds()
+        public void AddTagHelperDirective_WithQuotes_InvalidLookupText_AddsError()
         {
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo"),
+                    new SourceLocation(15, 0, 15),
+                    length: 3)
+            };
+
             ParseBlockTest("@addTagHelper \"Foo\"",
                 new DirectiveBlock(
                     Factory.CodeTransition(),
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo\"")
-                        .AsAddTagHelper("\"Foo\"")));
+                        .AsAddTagHelper(
+                            "\"Foo\"",
+                            "Foo",
+                            legacyErrors: expectedErrors)));
         }
 
         [Fact]
-        public void AddTagHelperDirectiveSupportsSpaces()
+        public void AddTagHelperDirective_SupportsSpaces()
         {
             ParseBlockTest("@addTagHelper     Foo,   Bar    ",
                 new DirectiveBlock(
@@ -1270,16 +1368,28 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + "     ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo,   Bar    ")
-                        .AsAddTagHelper("Foo,   Bar")));
+                        .AsAddTagHelper(
+                            "Foo,   Bar",
+                            "Foo,   Bar",
+                            "Foo",
+                            "Bar")
+                        .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
         [Fact]
-        public void AddTagHelperDirectiveRequiresValue()
+        public void AddTagHelperDirective_RequiresValue()
         {
             // Arrange
-            var expectedError = new RazorError(
+            var expectedErrors = new[]
-                LegacyResources.FormatParseError_DirectiveMustHaveValue(SyntaxConstants.CSharp.AddTagHelperKeyword),
+            {
-                absoluteIndex: 1, lineIndex: 0, columnIndex: 1, length: 12);
+                new RazorError(
+                    LegacyResources.FormatParseError_DirectiveMustHaveValue(SyntaxConstants.CSharp.AddTagHelperKeyword),
+                    absoluteIndex: 1, lineIndex: 0, columnIndex: 1, length: 12),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText(string.Empty),
+                    new SourceLocation(14, 0, 14),
+                    length: 1),
+            };
 
             // Act & Assert
             ParseBlockTest("@addTagHelper ",
@@ -1288,7 +1398,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.EmptyCSharp()
-                        .AsAddTagHelper(string.Empty, expectedError)
+                        .AsAddTagHelper(string.Empty, string.Empty, legacyErrors: expectedErrors)
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
@@ -1303,7 +1413,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 14, lineIndex: 0, columnIndex: 14, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.AddTagHelperKeyword),
-                    absoluteIndex: 14, lineIndex: 0, columnIndex: 14, length: 4)
+                    absoluteIndex: 14, lineIndex: 0, columnIndex: 14, length: 4),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("\"Foo"),
+                    new SourceLocation(14, 0, 14),
+                    length: 4),
             };
 
             // Act & Assert
@@ -1313,7 +1427,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("\"Foo")
-                        .AsAddTagHelper("\"Foo", expectedErrors)));
+                        .AsAddTagHelper("\"Foo", "\"Foo", legacyErrors: expectedErrors)));
         }
 
         [Fact]
@@ -1327,7 +1441,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     absoluteIndex: 17, lineIndex: 0, columnIndex: 17, length: 1),
                 new RazorError(
                     LegacyResources.FormatParseError_IncompleteQuotesAroundDirective(SyntaxConstants.CSharp.AddTagHelperKeyword),
-                    absoluteIndex: 14, lineIndex: 0, columnIndex: 14, length: 4)
+                    absoluteIndex: 14, lineIndex: 0, columnIndex: 14, length: 4),
+                new RazorError(
+                    Resources.FormatInvalidTagHelperLookupText("Foo\""),
+                    new SourceLocation(14, 0, 14),
+                    length: 4),
             };
 
             // Act & Assert
@@ -1337,7 +1455,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode(SyntaxConstants.CSharp.AddTagHelperKeyword + " ")
                            .Accepts(AcceptedCharactersInternal.None),
                     Factory.Code("Foo\"")
-                        .AsAddTagHelper("Foo\"", expectedErrors)
+                        .AsAddTagHelper("Foo\"", "Foo\"", legacyErrors: expectedErrors)
                         .Accepts(AcceptedCharactersInternal.AnyExceptNewline)));
         }
 
@@ -1611,6 +1729,245 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                     Factory.MetaCode("namespace").Accepts(AcceptedCharactersInternal.None)));
         }
 
+        public static TheoryData InvalidTagHelperPrefixData
+        {
+            get
+            {
+                var directiveLocation = new SourceLocation(1, 2, 3);
+
+                var invalidTagHelperPrefixValueError =
+                    "Invalid tag helper directive '{0}' value. '{1}' is not allowed in prefix '{2}'.";
+
+                return new TheoryData<string, SourceLocation, IEnumerable<RazorError>>
+                {
+                    {
+                        "th ",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    ' ',
+                                    "th "),
+                                directiveLocation,
+                                length: 3)
+                        }
+                    },
+                    {
+                        "th\t",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    '\t',
+                                    "th\t"),
+                                directiveLocation,
+                                length: 3)
+                        }
+                    },
+                    {
+                        "th" + Environment.NewLine,
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    Environment.NewLine[0],
+                                    "th" + Environment.NewLine),
+                                directiveLocation,
+                                length: 2 + Environment.NewLine.Length)
+                        }
+                    },
+                    {
+                        " th ",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    ' ',
+                                    " th "),
+                                directiveLocation,
+                                length: 4)
+                        }
+                    },
+                    {
+                        "@",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    '@',
+                                    "@"),
+                                directiveLocation,
+                                length: 1)
+                        }
+                    },
+                    {
+                        "t@h",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    '@',
+                                    "t@h"),
+                                directiveLocation,
+                                length: 3)
+                        }
+                    },
+                    {
+                        "!",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    '!',
+                                    "!"),
+                                directiveLocation,
+                                length: 1)
+                        }
+                    },
+                    {
+                        "!th",
+                        directiveLocation,
+                        new[]
+                        {
+                            new RazorError(
+                                string.Format(
+                                    invalidTagHelperPrefixValueError,
+                                    SyntaxConstants.CSharp.TagHelperPrefixKeyword,
+                                    '!',
+                                    "!th"),
+                                directiveLocation,
+                                length: 3)
+                        }
+                    },
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(InvalidTagHelperPrefixData))]
+        public void ValidateTagHelperPrefix_ValidatesPrefix(
+            string directiveText,
+            SourceLocation directiveLocation,
+            object expectedErrors)
+        {
+            // Arrange
+            var expectedDiagnostics = ((IEnumerable<RazorError>)expectedErrors).Select(RazorDiagnostic.Create);
+            var source = TestRazorSourceDocument.Create();
+            var options = RazorParserOptions.CreateDefault();
+            var context = new ParserContext(source, options);
+
+            var parser = new CSharpCodeParser(context);
+            var diagnostics = new List<RazorDiagnostic>();
+
+            // Act
+            parser.ValidateTagHelperPrefix(directiveText, directiveLocation, diagnostics);
+
+            // Assert
+            Assert.Equal(expectedDiagnostics, diagnostics);
+        }
+
+        [Theory]
+        [InlineData("foo,assemblyName", 4)]
+        [InlineData("foo, assemblyName", 5)]
+        [InlineData("   foo, assemblyName", 8)]
+        [InlineData("   foo   , assemblyName", 11)]
+        [InlineData("foo,    assemblyName", 8)]
+        [InlineData("   foo   ,    assemblyName   ", 14)]
+        public void ParseAddOrRemoveDirective_CalculatesAssemblyLocationInLookupText(string text, int assemblyLocation)
+        {
+            // Arrange
+            var source = TestRazorSourceDocument.Create();
+            var options = RazorParserOptions.CreateDefault();
+            var context = new ParserContext(source, options);
+
+            var parser = new CSharpCodeParser(context);
+
+            var directive = new CSharpCodeParser.ParsedDirective()
+            {
+                DirectiveText = text,
+            };
+
+            var diagnostics = new List<RazorDiagnostic>();
+            var expected = new SourceLocation(assemblyLocation, 0, assemblyLocation);
+
+            // Act
+            var result = parser.ParseAddOrRemoveDirective(directive, SourceLocation.Zero, diagnostics);
+
+            // Assert
+            Assert.Empty(diagnostics);
+            Assert.Equal("foo", result.TypePattern);
+            Assert.Equal("assemblyName", result.AssemblyName);
+        }
+
+        [Theory]
+        [InlineData("", 1)]
+        [InlineData("*,", 2)]
+        [InlineData("?,", 2)]
+        [InlineData(",", 1)]
+        [InlineData(",,,", 3)]
+        [InlineData("First, ", 7)]
+        [InlineData("First , ", 8)]
+        [InlineData(" ,Second", 8)]
+        [InlineData(" , Second", 9)]
+        [InlineData("SomeType,", 9)]
+        [InlineData("SomeAssembly", 12)]
+        [InlineData("First,Second,Third", 18)]
+        public void ParseAddOrRemoveDirective_CreatesErrorIfInvalidLookupText_DoesNotThrow(string directiveText, int errorLength)
+        {
+            // Arrange
+            var source = TestRazorSourceDocument.Create();
+            var options = RazorParserOptions.CreateDefault();
+            var context = new ParserContext(source, options);
+
+            var parser = new CSharpCodeParser(context);
+
+            var expectedErrorMessage = string.Format(
+                "Invalid tag helper directive look up text '{0}'. The correct look up text " +
+                "format is: \"name, assemblyName\".",
+                directiveText);
+
+            var directive = new CSharpCodeParser.ParsedDirective()
+            {
+                DirectiveText = directiveText
+            };
+
+            var diagnostics = new List<RazorDiagnostic>();
+            var expectedError = RazorDiagnostic.Create(
+                new RazorError(
+                    expectedErrorMessage,
+                    new SourceLocation(1, 2, 3),
+                    errorLength));
+
+            // Act
+            var result = parser.ParseAddOrRemoveDirective(directive, new SourceLocation(1, 2, 3), diagnostics);
+
+            // Assert
+            Assert.Same(directive, result);
+
+            var error = Assert.Single(diagnostics);
+            Assert.Equal(expectedError, error);
+        }
 
         internal virtual void ParseCodeBlockTest(
             string document,

test/Microsoft.AspNetCore.Razor.Language.Test/TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives_DesignTime.diagnostics.txt

@@ -1,14 +1,21 @@
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(3,2): Error RZ9999: Directive 'addTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(3,14): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(4,2): Error RZ9999: Directive 'addTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(4,15): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(5,15): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(5,15): Error RZ9999: Invalid tag helper directive look up text '"'. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(7,2): Error RZ9999: Directive 'removeTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(7,17): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(8,2): Error RZ9999: Directive 'removeTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(8,18): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(9,18): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(9,18): Error RZ9999: Invalid tag helper directive look up text '"'. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(11,2): Error RZ9999: Directive 'tagHelperPrefix' must have a value.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(12,2): Error RZ9999: Directive 'tagHelperPrefix' must have a value.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(12,1): Error RZ2001: The 'tagHelperPrefix' directive may only occur once per document.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,18): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,1): Error RZ2001: The 'tagHelperPrefix' directive may only occur once per document.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,18): Error RZ9999: Invalid tag helper directive 'tagHelperPrefix' value. '"' is not allowed in prefix '"'.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(15,10): Error RZ9999: The 'inherits' directive expects a type name.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(16,1): Error RZ9999: The 'inherits' directive may only occur once per document.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(16,11): Error RZ9999: The 'inherits' directive expects a type name.

test/Microsoft.AspNetCore.Razor.Language.Test/TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives_Runtime.diagnostics.txt

@@ -1,14 +1,21 @@
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(3,2): Error RZ9999: Directive 'addTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(3,14): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(4,2): Error RZ9999: Directive 'addTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(4,15): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(5,15): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(5,15): Error RZ9999: Invalid tag helper directive look up text '"'. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(7,2): Error RZ9999: Directive 'removeTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(7,17): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(8,2): Error RZ9999: Directive 'removeTagHelper' must have a value.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(8,18): Error RZ9999: Invalid tag helper directive look up text ''. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(9,18): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(9,18): Error RZ9999: Invalid tag helper directive look up text '"'. The correct look up text format is: "name, assemblyName".
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(11,2): Error RZ9999: Directive 'tagHelperPrefix' must have a value.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(12,2): Error RZ9999: Directive 'tagHelperPrefix' must have a value.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(12,1): Error RZ2001: The 'tagHelperPrefix' directive may only occur once per document.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,18): Error RZ9999: Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,1): Error RZ2001: The 'tagHelperPrefix' directive may only occur once per document.
+TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(13,18): Error RZ9999: Invalid tag helper directive 'tagHelperPrefix' value. '"' is not allowed in prefix '"'.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(15,10): Error RZ9999: The 'inherits' directive expects a type name.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(16,1): Error RZ9999: The 'inherits' directive may only occur once per document.
 TestFiles/IntegrationTests/CodeGenerationIntegrationTest/IncompleteDirectives.cshtml(16,11): Error RZ9999: The 'inherits' directive expects a type name.

test/Microsoft.AspNetCore.Razor.Test.Common/Language/Legacy/TestSpanBuilder.cs

@@ -334,27 +334,37 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             return _self.With(SpanChunkGenerator.Null);
         }
 
-        public SpanConstructor AsAddTagHelper(string lookupText, params RazorError[] legacyErrors)
+        public SpanConstructor AsAddTagHelper(
+            string lookupText,
+            string directiveText,
+            string typePattern = null,
+            string assemblyName = null,
+            params RazorError[] legacyErrors)
         {
             var diagnostics = legacyErrors.Select(error => RazorDiagnostic.Create(error)).ToList();
             return _self
-                .With(new AddTagHelperChunkGenerator(lookupText, diagnostics))
+                .With(new AddTagHelperChunkGenerator(lookupText, directiveText, typePattern, assemblyName, diagnostics))
                 .Accepts(AcceptedCharactersInternal.AnyExceptNewline);
         }
 
-        public SpanConstructor AsRemoveTagHelper(string lookupText, params RazorError[] legacyErrors)
+        public SpanConstructor AsRemoveTagHelper(
+            string lookupText,
+            string directiveText,
+            string typePattern = null,
+            string assemblyName = null,
+            params RazorError[] legacyErrors)
         {
             var diagnostics = legacyErrors.Select(error => RazorDiagnostic.Create(error)).ToList();
             return _self
-                .With(new RemoveTagHelperChunkGenerator(lookupText, diagnostics))
+                .With(new RemoveTagHelperChunkGenerator(lookupText, directiveText, typePattern, assemblyName, diagnostics))
                 .Accepts(AcceptedCharactersInternal.AnyExceptNewline);
         }
 
-        public SpanConstructor AsTagHelperPrefixDirective(string prefix, params RazorError[] legacyErrors)
+        public SpanConstructor AsTagHelperPrefixDirective(string prefix, string directiveText, params RazorError[] legacyErrors)
         {
             var diagnostics = legacyErrors.Select(error => RazorDiagnostic.Create(error)).ToList();
             return _self
-                .With(new TagHelperPrefixDirectiveChunkGenerator(prefix, diagnostics))
+                .With(new TagHelperPrefixDirectiveChunkGenerator(prefix, directiveText, diagnostics))
                 .Accepts(AcceptedCharactersInternal.AnyExceptNewline);
         }