Change ParserContext to take a RazorSourceDocument.

- This moves ParserContext closer to operating on a RazorSourceDocument and exposes it at the parsing layer.
- Was not able to replace the `ITextDocument` property on `ParserContext` due to its current wiring. Our tokenizers rely on a single reader that iterates over the document and take turns tokenizing characters from that reader. The reader that the tokenizers pull from is also highly coupled with the parsers implementations; they end up moving the readers pointer frequently.

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

@@ -9,14 +9,18 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 {
     internal partial class ParserContext
     {
-        public ParserContext(ITextDocument source, RazorParserOptions options)
+        public ParserContext(RazorSourceDocument source, RazorParserOptions options)
         {
             if (source == null)
             {
                 throw new ArgumentNullException(nameof(source));
             }
 
-            Source = source;
+            SourceDocument = source;
+            var chars = new char[source.Length];
+            source.CopyTo(0, chars, 0, source.Length);
+
+            Source = new SeekableTextReader(chars, source.FileName);
             DesignTimeMode = options.DesignTime;
             ParseOnlyLeadingDirectives = options.ParseOnlyLeadingDirectives;
             Builder = new SyntaxTreeBuilder();
@@ -29,6 +33,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         public ITextDocument Source { get; }
 
+        public RazorSourceDocument SourceDocument { get; }
+
         public bool DesignTimeMode { get; }
 
         public bool ParseOnlyLeadingDirectives { get; }

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

@@ -32,13 +32,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
                 throw new ArgumentNullException(nameof(source));
             }
 
-            var chars = new char[source.Length];
+            var context = new ParserContext(source, Options);
-            source.CopyTo(0, chars, 0, source.Length);
-
-            var reader = new SeekableTextReader(chars, source.FileName);
-
-            var context = new ParserContext(reader, Options);
-
             var codeParser = new CSharpCodeParser(Options.Directives, context);
             var markupParser = new HtmlMarkupParser(context);
 

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

@@ -1,8 +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 Microsoft.AspNetCore.Razor.Language.Legacy;
-
 namespace Microsoft.AspNetCore.Razor.Language
 {
     public abstract class RazorSourceLineCollection

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

@@ -34,11 +34,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         internal virtual RazorSyntaxTree ParseDocument(string document, bool designTime = false)
         {
-            var source = TestRazorSourceDocument.Create(document);
+            var source = TestRazorSourceDocument.Create(document, fileName: null);
-            var reader = new SeekableTextReader(document, filePath: null);
-
             var options = RazorParserOptions.Create(Array.Empty<DirectiveDescriptor>(), designTime);
-            var context = new ParserContext(reader, options);
+            var context = new ParserContext(source, options);
 
             var codeParser = new CSharpCodeParser(context);
             var markupParser = new HtmlMarkupParser(context);
@@ -64,26 +62,22 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
 
         internal virtual RazorSyntaxTree ParseHtmlBlock(string document, bool designTime = false)
         {
-            var source = TestRazorSourceDocument.Create(document);
+            var source = TestRazorSourceDocument.Create(document, fileName: null);
+            var options = RazorParserOptions.Create(Array.Empty<DirectiveDescriptor>(), designTime);
+            var context = new ParserContext(source, options);
 
-            using (var reader = new SeekableTextReader(document, filePath: null))
+            var parser = new HtmlMarkupParser(context);
+            parser.CodeParser = new CSharpCodeParser(context)
             {
-                var options = RazorParserOptions.Create(Array.Empty<DirectiveDescriptor>(), designTime);
+                HtmlParser = parser,
-                var context = new ParserContext(reader, options);
+            };
 
-                var parser = new HtmlMarkupParser(context);
+            parser.ParseBlock();
-                parser.CodeParser = new CSharpCodeParser(context)
-                {
-                    HtmlParser = parser,
-                };
 
-                parser.ParseBlock();
+            var root = context.Builder.Build();
+            var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
 
-                var root = context.Builder.Build();
+            return RazorSyntaxTree.Create(root, source, diagnostics, options);
-                var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
-
-                return RazorSyntaxTree.Create(root, source, diagnostics, options);
-            }
         }
 
         internal virtual RazorSyntaxTree ParseCodeBlock(string document, bool designTime = false)
@@ -96,26 +90,22 @@ namespace Microsoft.AspNetCore.Razor.Language.Legacy
             IEnumerable<DirectiveDescriptor> descriptors,
             bool designTime)
         {
-            var source = TestRazorSourceDocument.Create(document);
+            var source = TestRazorSourceDocument.Create(document, fileName: null);
+            var options = RazorParserOptions.Create(descriptors, designTime);
+            var context = new ParserContext(source, options);
 
-            using (var reader = new SeekableTextReader(document, filePath: null))
+            var parser = new CSharpCodeParser(descriptors, context);
+            parser.HtmlParser = new HtmlMarkupParser(context)
             {
-                var options = RazorParserOptions.Create(descriptors, designTime);
+                CodeParser = parser,
-                var context = new ParserContext(reader, options);
+            };
 
-                var parser = new CSharpCodeParser(descriptors, context);
+            parser.ParseBlock();
-                parser.HtmlParser = new HtmlMarkupParser(context)
-                {
-                    CodeParser = parser,
-                };
 
-                parser.ParseBlock();
+            var root = context.Builder.Build();
+            var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
 
-                var root = context.Builder.Build();
+            return RazorSyntaxTree.Create(root, source, diagnostics, options);
-                var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
-
-                return RazorSyntaxTree.Create(root, source, diagnostics, options);
-            }
         }
 
         internal SpanFactory CreateSpanFactory()