Use shared instances of NodeWriter classes (#12362)

Several of the NodeWriter classes don't have state and can have a shared instance used among callers. These allocations aren't huge in the profiles, but the RazorEditingTests.ScrollingAndTypingInCohosting speedometer test shows about 3 MB of allocating these in the CodeAnalysis process.

Author: ToddGrun

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/CodeGeneration/DesignTimeNodeWriterTest.cs

@@ -21,7 +21,7 @@ protected override void ConfigureCodeDocumentProcessor(RazorCodeDocumentProcesso
     public void WriteUsingDirective_NoSource_WritesContent()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new UsingDirectiveIntermediateNode()
@@ -45,7 +45,7 @@ public void WriteUsingDirective_NoSource_WritesContent()
     public void WriteUsingDirective_WithSource_WritesContentWithLinePragmaAndMapping()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var originalSpan = new SourceSpan("test.cshtml", 0, 0, 0, 6);
@@ -81,7 +81,7 @@ public void WriteUsingDirective_WithSource_WritesContentWithLinePragmaAndMapping
     public void WriteUsingDirective_WithSourceAndLineDirectives_WritesContentWithLinePragmaAndMapping()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var originalSpan = new SourceSpan("test.cshtml", 0, 0, 0, 6);
@@ -120,7 +120,7 @@ public void WriteUsingDirective_WithSourceAndLineDirectives_WritesContentWithLin
     public void WriteCSharpExpression_SkipsLinePragma_WithoutSource()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpExpressionIntermediateNode();
@@ -143,7 +143,7 @@ public void WriteCSharpExpression_SkipsLinePragma_WithoutSource()
     public void WriteCSharpExpression_WritesLinePragma_WithSource()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpExpressionIntermediateNode()
@@ -178,7 +178,7 @@ public void WriteCSharpExpression_WritesLinePragma_WithSource()
     public void WriteCSharpExpression_WithExtensionNode_WritesPadding()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpExpressionIntermediateNode();
@@ -207,7 +207,7 @@ public void WriteCSharpExpression_WithExtensionNode_WritesPadding()
     public void WriteCSharpExpression_WithSource_WritesPadding()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpExpressionIntermediateNode()
@@ -246,7 +246,7 @@ public void WriteCSharpExpression_WithSource_WritesPadding()
     public void WriteCSharpCode_WhitespaceContentWithSource_WritesContent()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpCodeIntermediateNode()
@@ -280,7 +280,7 @@ public void WriteCSharpCode_WhitespaceContentWithSource_WritesContent()
     public void WriteCSharpCode_SkipsLinePragma_WithoutSource()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpCodeIntermediateNode();
@@ -303,7 +303,7 @@ public void WriteCSharpCode_SkipsLinePragma_WithoutSource()
     public void WriteCSharpCode_WritesLinePragma_WithSource()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpCodeIntermediateNode()
@@ -337,7 +337,7 @@ public void WriteCSharpCode_WritesLinePragma_WithSource()
     public void WriteCSharpCode_WritesPadding_WithSource()
     {
         // Arrange
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         var node = new CSharpCodeIntermediateNode()
@@ -370,14 +370,14 @@ public void WriteCSharpCode_WritesPadding_WithSource()
     [Fact]
     public void WriteCSharpExpressionAttributeValue_RendersCorrectly()
     {
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
 
         var content = "<input checked=\"hello-world @false\" />";
         var source = TestRazorSourceDocument.Create(content);
         var codeDocument = ProjectEngine.CreateCodeDocument(source);
         var processor = CreateCodeDocumentProcessor(codeDocument);
         var documentNode = processor.GetDocumentNode();
-        var node = documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1] as CSharpExpressionAttributeValueIntermediateNode;
+        var node = (CSharpExpressionAttributeValueIntermediateNode)documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1];
 
         using var context = TestCodeRenderingContext.CreateDesignTime(source: source);
 
@@ -403,13 +403,13 @@ public void WriteCSharpExpressionAttributeValue_RendersCorrectly()
     [Fact]
     public void WriteCSharpCodeAttributeValue_RendersCorrectly()
     {
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         var content = "<input checked=\"hello-world @if(@true){ }\" />";
         var sourceDocument = TestRazorSourceDocument.Create(content);
         var codeDocument = ProjectEngine.CreateCodeDocument(sourceDocument);
         var processor = CreateCodeDocumentProcessor(codeDocument);
         var documentNode = processor.GetDocumentNode();
-        var node = documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1] as CSharpCodeAttributeValueIntermediateNode;
+        var node = (CSharpCodeAttributeValueIntermediateNode)documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1];
 
         using var context = TestCodeRenderingContext.CreateDesignTime(source: sourceDocument);
 
@@ -435,13 +435,13 @@ public void WriteCSharpCodeAttributeValue_RendersCorrectly()
     [Fact]
     public void WriteCSharpCodeAttributeValue_WithExpression_RendersCorrectly()
     {
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         var content = "<input checked=\"hello-world @if(@true){ @false }\" />";
         var source = TestRazorSourceDocument.Create(content);
         var codeDocument = ProjectEngine.CreateCodeDocument(source);
         var processor = CreateCodeDocumentProcessor(codeDocument);
         var documentNode = processor.GetDocumentNode();
-        var node = documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1] as CSharpCodeAttributeValueIntermediateNode;
+        var node = (CSharpCodeAttributeValueIntermediateNode)documentNode.Children.OfType<HtmlAttributeIntermediateNode>().Single().Children[1];
 
         using var context = TestCodeRenderingContext.CreateDesignTime(source: source);
 
@@ -484,7 +484,7 @@ Render Children
     [InlineData(@"\\SERVER/pages\test.cshtml",      @"\\SERVER\pages\test.cshtml")]
     public void LinePragma_Is_Adjusted_On_Windows(string fileName, string expectedFileName)
     {
-        var writer = new DesignTimeNodeWriter();
+        var writer = DesignTimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime();
 
         Assert.True(context.Options.RemapLinePragmaPathsOnWindows);
@@ -528,7 +528,7 @@ public void LinePragma_Is_Adjusted_On_Windows(string fileName, string expectedFi
     [InlineData(@"\\SERVER/pages\test.cshtml",      @"\\SERVER\pages\test.cshtml")]
     public void LinePragma_Enhanced_Is_Adjusted_On_Windows(string fileName, string expectedFileName)
     {
-        var writer = new RuntimeNodeWriter();
+        var writer = RuntimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateDesignTime(source: RazorSourceDocument.Create("", fileName));
 
         Assert.True(context.Options.RemapLinePragmaPathsOnWindows);

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/CodeGeneration/LiteralRuntimeNodeWriterTest.cs

@@ -12,7 +12,7 @@ public class LiteralRuntimeNodeWriterTest
     public void WriteCSharpExpression_UsesWriteLiteral_WritesLinePragma_WithSource()
     {
         // Arrange
-        var writer = new LiteralRuntimeNodeWriter();
+        var writer = LiteralRuntimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateRuntime();
 
         var node = new CSharpExpressionIntermediateNode();
@@ -43,7 +43,7 @@ public void WriteCSharpExpression_UsesWriteLiteral_WritesLinePragma_WithSource()
     public void WriteCSharpExpression_WithMultipleChildren()
     {
         // Arrange
-        var writer = new LiteralRuntimeNodeWriter();
+        var writer = LiteralRuntimeNodeWriter.Instance;
         using var context = TestCodeRenderingContext.CreateRuntime();
 
         var node = new CSharpExpressionIntermediateNode();