[Fixes #1195] Add a way to parse just until the first directive

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

@@ -10,7 +10,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class CSharpCodeParser : TokenizerBackedParser<CSharpTokenizer, CSharpSymbol, CSharpSymbolType>
     {
-        internal static readonly int UsingKeywordLength = 5; // using
         private static readonly Func<CSharpSymbol, bool> IsValidStatementSpacingSymbol =
             IsSpacingToken(includeNewLines: true, includeComments: true);
 
@@ -88,7 +87,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         }
 
         public CSharpCodeParser(IEnumerable<DirectiveDescriptor> directiveDescriptors, ParserContext context)
-            : base(CSharpLanguageCharacteristics.Instance, context)
+            : base(context.StopParsingAfterFirstDirective ? FirstDirectiveCSharpLanguageCharacteristics.Instance : CSharpLanguageCharacteristics.Instance, context)
         {
             Keywords = new HashSet<string>();
             SetUpKeywords();
@@ -106,7 +105,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         protected void MapDirectives(Action handler, params string[] directives)
         {
-            foreach (string directive in directives)
+            foreach (var directive in directives)
             {
                 _directiveParsers.Add(directive, handler);
                 Keywords.Add(directive);
@@ -143,7 +142,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         private void MapKeywords(Action<bool> handler, bool topLevel, params CSharpKeyword[] keywords)
         {
-            foreach (CSharpKeyword keyword in keywords)
+            foreach (var keyword in keywords)
             {
                 _keywordParsers.Add(keyword, handler);
                 if (topLevel)
@@ -587,17 +586,17 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         private void CaptureWhitespaceAtEndOfCodeOnlyLine()
         {
-            IEnumerable<CSharpSymbol> ws = ReadWhile(sym => sym.Type == CSharpSymbolType.WhiteSpace);
+            var whitespace = ReadWhile(sym => sym.Type == CSharpSymbolType.WhiteSpace);
             if (At(CSharpSymbolType.NewLine))
             {
-                Accept(ws);
+                Accept(whitespace);
                 AcceptAndMoveNext();
                 PutCurrentBack();
             }
             else
             {
                 PutCurrentBack();
-                PutBack(ws);
+                PutBack(whitespace);
             }
         }
 
@@ -807,11 +806,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         private void WhileClause()
         {
             Span.EditHandler.AcceptedCharacters = AcceptedCharacters.Any;
-            IEnumerable<CSharpSymbol> ws = SkipToNextImportantToken();
+            var whitespace = SkipToNextImportantToken();
 
             if (At(CSharpKeyword.While))
             {
-                Accept(ws);
+                Accept(whitespace);
                 Assert(CSharpKeyword.While);
                 AcceptAndMoveNext();
                 AcceptWhile(IsSpacingToken(includeNewLines: true, includeComments: true));
@@ -823,7 +822,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             else
             {
                 PutCurrentBack();
-                PutBack(ws);
+                PutBack(whitespace);
             }
         }
 
@@ -1042,12 +1041,12 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         private void AfterIfClause()
         {
             // Grab whitespace and razor comments
-            IEnumerable<CSharpSymbol> ws = SkipToNextImportantToken();
+            var whitespace = SkipToNextImportantToken();
 
             // Check for an else part
             if (At(CSharpKeyword.Else))
             {
-                Accept(ws);
+                Accept(whitespace);
                 Assert(CSharpKeyword.Else);
                 ElseClause();
             }
@@ -1055,7 +1054,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             {
                 // No else, return whitespace
                 PutCurrentBack();
-                PutBack(ws);
+                PutBack(whitespace);
                 Span.EditHandler.AcceptedCharacters = AcceptedCharacters.Any;
             }
         }
@@ -1355,13 +1354,15 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             while (!EndOfFile)
             {
                 var bookmark = CurrentStart.AbsoluteIndex;
-                IEnumerable<CSharpSymbol> read = ReadWhile(sym => sym.Type != CSharpSymbolType.Semicolon &&
+                var read = ReadWhile(sym =>
-                                                                  sym.Type != CSharpSymbolType.RazorCommentTransition &&
+                    sym.Type != CSharpSymbolType.Semicolon &&
-                                                                  sym.Type != CSharpSymbolType.Transition &&
+                    sym.Type != CSharpSymbolType.RazorCommentTransition &&
-                                                                  sym.Type != CSharpSymbolType.LeftBrace &&
+                    sym.Type != CSharpSymbolType.Transition &&
-                                                                  sym.Type != CSharpSymbolType.LeftParenthesis &&
+                    sym.Type != CSharpSymbolType.LeftBrace &&
-                                                                  sym.Type != CSharpSymbolType.LeftBracket &&
+                    sym.Type != CSharpSymbolType.LeftParenthesis &&
-                                                                  sym.Type != CSharpSymbolType.RightBrace);
+                    sym.Type != CSharpSymbolType.LeftBracket &&
+                    sym.Type != CSharpSymbolType.RightBrace);
+
                 if (At(CSharpSymbolType.LeftBrace) ||
                     At(CSharpSymbolType.LeftParenthesis) ||
                     At(CSharpSymbolType.LeftBracket))
@@ -1443,8 +1444,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         private void HandleKeyword(bool topLevel, Action fallback)
         {
             Debug.Assert(CurrentSymbol.Type == CSharpSymbolType.Keyword && CurrentSymbol.Keyword != null);
-            Action<bool> handler;
+            if (_keywordParsers.TryGetValue(CurrentSymbol.Keyword.Value, out var handler))
-            if (_keywordParsers.TryGetValue(CurrentSymbol.Keyword.Value, out handler))
             {
                 handler(topLevel);
             }
@@ -1458,16 +1458,16 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         {
             while (!EndOfFile)
             {
-                IEnumerable<CSharpSymbol> ws = ReadWhile(IsSpacingToken(includeNewLines: true, includeComments: true));
+                var whitespace = ReadWhile(IsSpacingToken(includeNewLines: true, includeComments: true));
                 if (At(CSharpSymbolType.RazorCommentTransition))
                 {
-                    Accept(ws);
+                    Accept(whitespace);
                     Span.EditHandler.AcceptedCharacters = AcceptedCharacters.Any;
                     RazorComment();
                 }
                 else
                 {
-                    return ws;
+                    return whitespace;
                 }
             }
             return Enumerable.Empty<CSharpSymbol>();
@@ -1814,7 +1814,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             }
 
             // Pull out the type name
-            string baseType = string.Concat(Span.Symbols.Select(s => s.Content));
+            var baseType = string.Concat(Span.Symbols.Select(s => s.Content));
 
             // Set up chunk generation
             Span.ChunkGenerator = createChunkGenerator(baseType.Trim());

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

@@ -63,7 +63,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             { CSharpSymbolType.Transition, "@" },
         };
 
-        private CSharpLanguageCharacteristics()
+        protected CSharpLanguageCharacteristics()
         {
         }
 
@@ -172,4 +172,4 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             return keyword.ToString().ToLowerInvariant();
         }
     }
-}
+}

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

@@ -0,0 +1,62 @@
+// 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.Diagnostics;
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    internal class DirectiveCSharpTokenizer : CSharpTokenizer
+    {
+        private bool _visitedFirstTokenStart = false;
+        private bool _visitedFirstTokenLineEnd = false;
+
+        public DirectiveCSharpTokenizer(ITextDocument source) : base(source)
+        {
+        }
+
+        protected override StateResult Dispatch()
+        {
+            var result = base.Dispatch();
+            if (result.Result != null && !_visitedFirstTokenStart && IsValidTokenType(result.Result.Type))
+            {
+                _visitedFirstTokenStart = true;
+            }
+            else if (result.Result != null && _visitedFirstTokenStart && result.Result.Type == CSharpSymbolType.NewLine)
+            {
+                _visitedFirstTokenLineEnd = true;
+            }
+
+            return result;
+        }
+
+        public override CSharpSymbol NextSymbol()
+        {
+            // Post-Condition: Buffer should be empty at the start of Next()
+            Debug.Assert(Buffer.Length == 0);
+            StartSymbol();
+
+            if (EndOfFile || (_visitedFirstTokenStart && _visitedFirstTokenLineEnd))
+            {
+                return null;
+            }
+
+            var symbol = Turn();
+
+            // Post-Condition: Buffer should be empty at the end of Next()
+            Debug.Assert(Buffer.Length == 0);
+
+            return symbol;
+        }
+
+        private bool IsValidTokenType(CSharpSymbolType type)
+        {
+            return type != CSharpSymbolType.WhiteSpace &&
+                type != CSharpSymbolType.NewLine &&
+                type != CSharpSymbolType.Comment &&
+                type != CSharpSymbolType.RazorComment &&
+                type != CSharpSymbolType.RazorCommentStar &&
+                type != CSharpSymbolType.RazorCommentTransition &&
+                type != CSharpSymbolType.Transition;
+        }
+    }
+}

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

@@ -0,0 +1,56 @@
+// 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.Diagnostics;
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    internal class DirectiveHtmlTokenizer : HtmlTokenizer
+    {
+        private bool _visitedFirstTokenStart = false;
+
+        public DirectiveHtmlTokenizer(ITextDocument source) : base(source)
+        {
+        }
+
+        protected override StateResult Dispatch()
+        {
+            var result = base.Dispatch();
+            if (result.Result != null && IsValidTokenType(result.Result.Type))
+            {
+                _visitedFirstTokenStart = true;
+            }
+
+            return result;
+        }
+
+        public override HtmlSymbol NextSymbol()
+        {
+            // Post-Condition: Buffer should be empty at the start of Next()
+            Debug.Assert(Buffer.Length == 0);
+            StartSymbol();
+
+            if (EndOfFile || _visitedFirstTokenStart)
+            {
+                return null;
+            }
+
+            var symbol = Turn();
+
+            // Post-Condition: Buffer should be empty at the end of Next()
+            Debug.Assert(Buffer.Length == 0);
+
+            return symbol;
+        }
+
+        private bool IsValidTokenType(HtmlSymbolType type)
+        {
+            return type != HtmlSymbolType.WhiteSpace &&
+                type != HtmlSymbolType.NewLine &&
+                type != HtmlSymbolType.RazorComment &&
+                type != HtmlSymbolType.RazorCommentStar &&
+                type != HtmlSymbolType.RazorCommentTransition &&
+                type != HtmlSymbolType.Transition;
+        }
+    }
+}

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

@@ -0,0 +1,18 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    internal class FirstDirectiveCSharpLanguageCharacteristics : CSharpLanguageCharacteristics
+    {
+        private static readonly FirstDirectiveCSharpLanguageCharacteristics _instance = new FirstDirectiveCSharpLanguageCharacteristics();
+
+        private FirstDirectiveCSharpLanguageCharacteristics()
+        {
+        }
+
+        public new static FirstDirectiveCSharpLanguageCharacteristics Instance => _instance;
+
+        public override CSharpTokenizer CreateTokenizer(ITextDocument source) => new DirectiveCSharpTokenizer(source);
+    }
+}

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

@@ -0,0 +1,18 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    internal class FirstDirectiveHtmlLanguageCharacteristics : HtmlLanguageCharacteristics
+    {
+        private static readonly FirstDirectiveHtmlLanguageCharacteristics _instance = new FirstDirectiveHtmlLanguageCharacteristics();
+
+        private FirstDirectiveHtmlLanguageCharacteristics()
+        {
+        }
+
+        public new static FirstDirectiveHtmlLanguageCharacteristics Instance => _instance;
+
+        public override HtmlTokenizer CreateTokenizer(ITextDocument source) => new DirectiveHtmlTokenizer(source);
+    }
+}

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

@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
     {
         private static readonly HtmlLanguageCharacteristics _instance = new HtmlLanguageCharacteristics();
 
-        private HtmlLanguageCharacteristics()
+        protected HtmlLanguageCharacteristics()
         {
         }
 
@@ -89,7 +89,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
                     Debug.Fail("FlipBracket must be called with a bracket character");
 #else
-                Debug.Assert(false, "FlipBracket must be called with a bracket character");
+                    Debug.Assert(false, "FlipBracket must be called with a bracket character");
 #endif
                     return HtmlSymbolType.Unknown;
             }
@@ -130,4 +130,4 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             return new HtmlSymbol(content, type, errors);
         }
     }
-}
+}

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

@@ -38,7 +38,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
         };
 
         public HtmlMarkupParser(ParserContext context)
-            : base(HtmlLanguageCharacteristics.Instance, context)
+            : base(context.StopParsingAfterFirstDirective ? FirstDirectiveHtmlLanguageCharacteristics.Instance : HtmlLanguageCharacteristics.Instance, context)
         {
         }
 

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

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.IO;
 
 namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {

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

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal partial class ParserContext
     {
-        public ParserContext(ITextDocument source, bool designTime)
+        public ParserContext(ITextDocument source, RazorParserOptions options)
         {
             if (source == null)
             {
@@ -17,7 +17,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             }
 
             Source = source;
-            DesignTimeMode = designTime;
+            DesignTimeMode = options.DesignTimeMode;
+            StopParsingAfterFirstDirective = options.StopParsingAfterFirstDirective;
             Builder = new SyntaxTreeBuilder();
             ErrorSink = new ErrorSink();
         }
@@ -30,6 +31,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         public bool DesignTimeMode { get; }
 
+        public bool StopParsingAfterFirstDirective { get; }
+
         public bool WhiteSpaceIsSignificantToAncestorBlock { get; set; }
 
         public bool NullGenerateWhitespaceAndNewLine { get; set; }

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

@@ -37,7 +37,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             var reader = new SeekableTextReader(chars, source.FileName);
 
-            var context = new ParserContext(reader, Options.DesignTimeMode);
+            var context = new ParserContext(reader, Options);
 
             var codeParser = new CSharpCodeParser(Options.Directives, context);
             var markupParser = new HtmlMarkupParser(context);

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

@@ -1,9 +1,6 @@
 // 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.Diagnostics;
-
 namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal class TokenizerView<TTokenizer, TSymbol, TSymbolType>

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

@@ -26,6 +26,8 @@ namespace Microsoft.AspNetCore.Razor.Language
 
         public bool IsIndentingWithTabs { get; set; }
 
+        public bool StopParsingAfterFirstDirective { get; set; }
+
         public ICollection<DirectiveDescriptor> Directives { get; }
 
         public HashSet<string> NamespaceImports { get; }

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

@@ -0,0 +1,47 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    public class DirectiveCSharpTokenizerTest : CSharpTokenizerTestBase
+    {
+        [Fact]
+        public void Next_ReturnsNull_AfterTokenizingFirstDirective()
+        {
+            TestTokenizer(
+                "\r\n @something \r\n @this is ignored",
+                new CSharpSymbol("\r\n", CSharpSymbolType.NewLine),
+                new CSharpSymbol(" ", CSharpSymbolType.WhiteSpace),
+                new CSharpSymbol("@", CSharpSymbolType.Transition),
+                new CSharpSymbol("something", CSharpSymbolType.Identifier),
+                new CSharpSymbol(" ", CSharpSymbolType.WhiteSpace),
+                new CSharpSymbol("\r\n", CSharpSymbolType.NewLine));
+        }
+
+        [Fact]
+        public void Next_IncludesComments_ReturnsNull_AfterTokenizingFirstDirective()
+        {
+            TestTokenizer(
+                "@*included*@\r\n @something   \"value\"\r\n @this is ignored",
+                new CSharpSymbol("@", CSharpSymbolType.RazorCommentTransition),
+                new CSharpSymbol("*", CSharpSymbolType.RazorCommentStar),
+                new CSharpSymbol("included", CSharpSymbolType.RazorComment),
+                new CSharpSymbol("*", CSharpSymbolType.RazorCommentStar),
+                new CSharpSymbol("@", CSharpSymbolType.RazorCommentTransition),
+                new CSharpSymbol("\r\n", CSharpSymbolType.NewLine),
+                new CSharpSymbol(" ", CSharpSymbolType.WhiteSpace),
+                new CSharpSymbol("@", CSharpSymbolType.Transition),
+                new CSharpSymbol("something", CSharpSymbolType.Identifier),
+                new CSharpSymbol("   ", CSharpSymbolType.WhiteSpace),
+                new CSharpSymbol("\"value\"", CSharpSymbolType.StringLiteral),
+                new CSharpSymbol("\r\n", CSharpSymbolType.NewLine));
+        }
+
+        internal override object CreateTokenizer(ITextDocument source)
+        {
+            return new DirectiveCSharpTokenizer(source);
+        }
+    }
+}

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

@@ -0,0 +1,41 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Language.Legacy
+{
+    public class DirectiveHtmlTokenizerTest : HtmlTokenizerTestBase
+    {
+        [Fact]
+        public void Next_ReturnsNull_WhenHtmlIsSeen()
+        {
+            TestTokenizer(
+                "\r\n <div>Ignored</div>",
+                new HtmlSymbol("\r\n", HtmlSymbolType.NewLine),
+                new HtmlSymbol(" ", HtmlSymbolType.WhiteSpace),
+                new HtmlSymbol("<", HtmlSymbolType.OpenAngle));
+        }
+
+        [Fact]
+        public void Next_IncludesRazorComments_ReturnsNull_WhenHtmlIsSeen()
+        {
+            TestTokenizer(
+                "\r\n @*included*@ <div>Ignored</div>",
+                new HtmlSymbol("\r\n", HtmlSymbolType.NewLine),
+                new HtmlSymbol(" ", HtmlSymbolType.WhiteSpace),
+                new HtmlSymbol("@", HtmlSymbolType.RazorCommentTransition),
+                new HtmlSymbol("*", HtmlSymbolType.RazorCommentStar),
+                new HtmlSymbol("included", HtmlSymbolType.RazorComment),
+                new HtmlSymbol("*", HtmlSymbolType.RazorCommentStar),
+                new HtmlSymbol("@", HtmlSymbolType.RazorCommentTransition),
+                new HtmlSymbol(" ", HtmlSymbolType.WhiteSpace),
+                new HtmlSymbol("<", HtmlSymbolType.OpenAngle));
+        }
+
+        internal override object CreateTokenizer(ITextDocument source)
+        {
+            return new DirectiveHtmlTokenizer(source);
+        }
+    }
+}

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

@@ -37,7 +37,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             var source = TestRazorSourceDocument.Create(document);
             var reader = new SeekableTextReader(document, filePath: null);
 
-            var context = new ParserContext(reader, designTime);
+            var options = RazorParserOptions.CreateDefaultOptions();
+            options.DesignTimeMode = designTime;
+            var context = new ParserContext(reader, options);
 
             var codeParser = new CSharpCodeParser(context);
             var markupParser = new HtmlMarkupParser(context);
@@ -49,8 +51,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             var root = context.Builder.Build();
             var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
-            var options = RazorParserOptions.CreateDefaultOptions();
-            options.DesignTimeMode = designTime;
 
             var tree = RazorSyntaxTree.Create(root, source, diagnostics, options);
             var defaultDirectivePass = new DefaultDirectiveSyntaxTreePass();
@@ -65,7 +65,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             using (var reader = new SeekableTextReader(document, filePath: null))
             {
-                var context = new ParserContext(reader, designTime);
+                var options = RazorParserOptions.CreateDefaultOptions();
+                options.DesignTimeMode = designTime;
+                var context = new ParserContext(reader, options);
 
                 var parser = new HtmlMarkupParser(context);
                 parser.CodeParser = new CSharpCodeParser(context)
@@ -77,8 +79,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
                 var root = context.Builder.Build();
                 var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
-                var options = RazorParserOptions.CreateDefaultOptions();
-                options.DesignTimeMode = designTime;
 
                 return RazorSyntaxTree.Create(root, source, diagnostics, options);
             }
@@ -98,7 +98,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
             using (var reader = new SeekableTextReader(document, filePath: null))
             {
-                var context = new ParserContext(reader, designTime);
+                var options = RazorParserOptions.CreateDefaultOptions();
+                options.DesignTimeMode = designTime;
+                var context = new ParserContext(reader, options);
 
                 var parser = new CSharpCodeParser(descriptors, context);
                 parser.HtmlParser = new HtmlMarkupParser(context)
@@ -111,9 +113,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                 var root = context.Builder.Build();
                 var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
 
-                var options = RazorParserOptions.CreateDefaultOptions();
-                options.DesignTimeMode = designTime;
-
                 options.Directives.Clear();
                 foreach (var directive in descriptors)
                 {

test/Microsoft.AspNetCore.Razor.Language.Test/RazorSyntaxTreeTest.cs

@@ -56,5 +56,24 @@ namespace Microsoft.AspNetCore.Razor.Language.Test
                 }
             }
         }
+
+        [Fact]
+        public void Parse_UseDirectiveTokenizer_ParsesUntilFirstDirective()
+        {
+            // Arrange
+            var source = TestRazorSourceDocument.Create("\r\n  \r\n    @*SomeComment*@ \r\n  @tagHelperPrefix \"SomePrefix\"\r\n<html>\r\n@if (true) {\r\n @if(false) { <div>@something.</div> } \r\n}");
+            var options = RazorParserOptions.CreateDefaultOptions();
+            options.StopParsingAfterFirstDirective = true;
+
+            // Act
+            var syntaxTree = RazorSyntaxTree.Parse(source, options);
+
+            // Assert
+            Assert.NotNull(syntaxTree);
+            Assert.Equal(6, syntaxTree.Root.Children.Count);
+            var block = Assert.IsType<Block>(syntaxTree.Root.Children[4]);
+            Assert.Equal(BlockKind.Directive, block.Type);
+            Assert.Empty(syntaxTree.Diagnostics);
+        }
     }
 }