RazorCodeDocument: Convert Get/SetFileKind to instance methods

Move the GetFileKind and SetFileKind extension methods to RazorCodeDocument and make them instance methods backed by a simple field.

Author: DustinCampbell

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/RazorCodeDocument.cs

@@ -15,6 +15,8 @@ public sealed class RazorCodeDocument
     public RazorParserOptions ParserOptions { get; }
     public RazorCodeGenerationOptions CodeGenerationOptions { get; }
 
+    private string? _fileKind;
+
     private RazorCodeDocument(
         RazorSourceDocument source,
         ImmutableArray<RazorSourceDocument> imports,
@@ -50,4 +52,12 @@ public static RazorCodeDocument Create(
 
         return new RazorCodeDocument(source, imports, parserOptions, codeGenerationOptions);
     }
+
+    public string? GetFileKind()
+        => _fileKind;
+
+    public void SetFileKind(string fileKind)
+    {
+        _fileKind = fileKind;
+    }
 }

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/RazorCodeDocumentExtensions.cs

@@ -202,26 +202,6 @@ public static void SetCSharpDocument(this RazorCodeDocument document, RazorCShar
         document.Items[typeof(RazorCSharpDocument)] = csharp;
     }
 
-    public static string GetFileKind(this RazorCodeDocument document)
-    {
-        if (document == null)
-        {
-            throw new ArgumentNullException(nameof(document));
-        }
-
-        return (string)document.Items[typeof(FileKinds)];
-    }
-
-    public static void SetFileKind(this RazorCodeDocument document, string fileKind)
-    {
-        if (document == null)
-        {
-            throw new ArgumentNullException(nameof(document));
-        }
-
-        document.Items[typeof(FileKinds)] = fileKind;
-    }
-
     public static string GetCssScope(this RazorCodeDocument document)
     {
         if (document == null)

src/Razor/test/Microsoft.VisualStudio.LegacyEditor.Razor.Test/Parsing/VisualStudioRazorParserIntegrationTest.cs

@@ -60,6 +60,7 @@ public async Task NoDocumentSnapshotParsesComponentFileCorrectly()
             Assert.Equal(1, manager._parseCount);
 
             var codeDocument = await manager.InnerParser.GetLatestCodeDocumentAsync(snapshot);
+            Assert.NotNull(codeDocument);
             Assert.Equal(FileKinds.Component, codeDocument.GetFileKind());
 
             // @code is only applicable in component files so we're verifying that `@code` was treated as a directive.