Remove ItemCollection from CodeRenderingContext (#10764)

Because of a dare from @333fred, I'm currently on a crusade to remove
`ItemCollection` from the Razor Compiler completely. Previously, I
removed `ItemCollection` from `TagHelperDescriptorProviderContext`
(#10720). This time, I'm removing it from `CodeRenderingContext`.

It turns out that every `CodeRenderingContext` greedily creates an
`ItemCollection`, though there are only ever two things stored there:

1. A string to use for new lines in `CodeWriter`.
2. A string representing "suppress IDs", which is already specified in
`RazorCodeGenerationOptions`.

These two items were really present as a hook that compiler tests could
set. However, it's much easier and less wasteful to elevate both items
to `RazorCodeGenerationOptions` and make tests set the options directly.

I made a few other refactorings as part of this change:

- I merged several abstract base classes with their single default
concrete type:
  - `CodeRenderingContext` and `DefaultCodeRenderingContext`
  - `RazorCSharpDocument` and `DefaultRazorCSharpDocument`,
  - `RazorCodeGenerationOptions` and `DefaultRazorCodeGenerationOptions`
- `RazorCodeGenerationOptionsBuilder` and
`DefaultRazorCodeGenerationOptionsBuilder`.
- Reworked `RazorCodeGenerationOptions` and introduced
`RazorCodeGenerationOptionsFlags` to track its boolean fields.
- Cleaned up `RazorCSharpDocument` and unified its collections on
`ImmutableArray<>` rather than `IReadOnlyList<>`.
- Enabled nullability annotations for several types.
- Used more pooled collections in `CodeRenderingContext`.

Note: I was careful with my commit history, and it should be clean
enough to review commit-by-commit if that's your preference.

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/IntegrationTests/CodeGenerationIntegrationTest.cs

@@ -66,7 +66,7 @@ public class MyService<TModel>
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Count > 0);
+        Assert.NotEmpty(compiled.CodeDocument.GetCSharpDocument().Diagnostics);
     }
 
     [Fact]

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/test/AssemblyAttributeInjectionPassTest.cs

@@ -19,7 +19,7 @@ public void Execute_NoOps_IfNamespaceNodeIsMissing()
         // Arrange
         var irDocument = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var pass = new AssemblyAttributeInjectionPass
@@ -40,7 +40,7 @@ public void Execute_NoOps_IfNamespaceNodeHasEmptyContent()
         // Arrange
         var irDocument = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode() { Content = string.Empty };
@@ -66,7 +66,7 @@ public void Execute_NoOps_IfClassNameNodeIsMissing()
         // Arrange
         var irDocument = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(irDocument);
@@ -93,7 +93,7 @@ public void Execute_NoOps_IfClassNameIsEmpty()
         // Arrange
         var irDocument = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode
@@ -134,7 +134,7 @@ public void Execute_NoOps_IfDocumentIsNotViewOrPage()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = "Default",
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode() { Content = "SomeNamespace" };
@@ -170,7 +170,7 @@ public void Execute_NoOps_ForDesignTime()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = MvcViewDocumentClassifierPass.MvcViewDocumentKind,
-            Options = RazorCodeGenerationOptions.CreateDesignTimeDefault(),
+            Options = RazorCodeGenerationOptions.DesignTimeDefault,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode
@@ -217,7 +217,7 @@ public void Execute_AddsRazorViewAttribute_ToViews()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = MvcViewDocumentClassifierPass.MvcViewDocumentKind,
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode
@@ -270,7 +270,7 @@ public void Execute_EscapesViewPathWhenAddingAttributeToViews()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = MvcViewDocumentClassifierPass.MvcViewDocumentKind,
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode
@@ -323,7 +323,7 @@ public void Execute_AddsRazorPagettribute_ToPage()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = RazorPageDocumentClassifierPass.RazorPageDocumentKind,
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var pageDirective = new DirectiveIntermediateNode
@@ -383,7 +383,7 @@ public void Execute_EscapesViewPathAndRouteWhenAddingAttributeToPage()
         var irDocument = new DocumentIntermediateNode
         {
             DocumentKind = MvcViewDocumentClassifierPass.MvcViewDocumentKind,
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
         var builder = IntermediateNodeBuilder.Create(irDocument);
         var @namespace = new NamespaceDeclarationIntermediateNode

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/test/InstrumentationPassTest.cs

@@ -18,7 +18,7 @@ public void InstrumentationPass_NoOps_ForDesignTime()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDesignTimeDefault(),
+            Options = RazorCodeGenerationOptions.DesignTimeDefault,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -50,7 +50,7 @@ public void InstrumentationPass_InstrumentsHtml()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -89,7 +89,7 @@ public void InstrumentationPass_SkipsHtml_WithoutLocation()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -121,7 +121,7 @@ public void InstrumentationPass_InstrumentsCSharpExpression()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -157,7 +157,7 @@ public void InstrumentationPass_SkipsCSharpExpression_WithoutLocation()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -188,7 +188,7 @@ public void InstrumentationPass_SkipsCSharpExpression_InsideTagHelperAttribute()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -239,7 +239,7 @@ public void InstrumentationPass_SkipsCSharpExpression_InsideTagHelperProperty()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -290,7 +290,7 @@ public void InstrumentationPass_InstrumentsTagHelper()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);
@@ -321,7 +321,7 @@ public void InstrumentationPass_SkipsTagHelper_WithoutLocation()
         // Arrange
         var document = new DocumentIntermediateNode()
         {
-            Options = RazorCodeGenerationOptions.CreateDefault(),
+            Options = RazorCodeGenerationOptions.Default,
         };
 
         var builder = IntermediateNodeBuilder.Create(document);

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/test/IntegrationTests/CodeGenerationIntegrationTest.cs

@@ -85,7 +85,7 @@ public class MyService<TModel>
         AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetCSharpDocument());
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Count > 0);
+        Assert.NotEmpty(compiled.CodeDocument.GetCSharpDocument().Diagnostics);
     }
 
     [Fact]
@@ -536,7 +536,7 @@ public class MyService<TModel>
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Count > 0);
+        Assert.NotEmpty(compiled.CodeDocument.GetCSharpDocument().Diagnostics);
     }
 
     [Fact]

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions/test/IntegrationTests/CodeGenerationIntegrationTest.cs

@@ -92,7 +92,7 @@ public class MyService<TModel>
         AssertLinePragmas(compiled.CodeDocument, designTime: false);
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Count > 0);
+        Assert.NotEmpty(compiled.CodeDocument.GetCSharpDocument().Diagnostics);
     }
 
     [Fact]
@@ -949,7 +949,7 @@ public class MyService<TModel>
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Count > 0);
+        Assert.NotEmpty(compiled.CodeDocument.GetCSharpDocument().Diagnostics);
     }
 
     [Fact]

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

@@ -402,7 +402,7 @@ public void CSharpCodeWriter_RespectTabSetting()
             o.IndentSize = 4;
         });
 
-        using var writer = new CodeWriter(Environment.NewLine, options);
+        using var writer = new CodeWriter(options);
 
         // Act
         writer.BuildClassDeclaration(Array.Empty<string>(), "C", "", Array.Empty<string>(), Array.Empty<TypeParameter>(), context: null);
@@ -428,7 +428,7 @@ public void CSharpCodeWriter_RespectSpaceSetting()
             o.IndentSize = 4;
         });
 
-        using var writer = new CodeWriter(Environment.NewLine, options);
+        using var writer = new CodeWriter(options);
 
         // Act
         writer.BuildClassDeclaration(Array.Empty<string>(), "C", "", Array.Empty<string>(), Array.Empty<TypeParameter>(), context: null);

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

@@ -15,7 +15,7 @@ public void CreateDefault_CreatesDefaultCodeTarget()
     {
         // Arrange
         var codeDocument = TestRazorCodeDocument.CreateEmpty();
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         // Act
         var target = CodeTarget.CreateDefault(codeDocument, options);
@@ -32,7 +32,7 @@ public void CreateDefault_CallsDelegate()
         Action<CodeTargetBuilder> @delegate = (b) => { wasCalled = true; };
 
         var codeDocument = TestRazorCodeDocument.CreateEmpty();
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         // Act
         CodeTarget.CreateDefault(codeDocument, options, @delegate);
@@ -46,7 +46,7 @@ public void CreateDefault_AllowsNullDelegate()
     {
         // Arrange
         var codeDocument = TestRazorCodeDocument.CreateEmpty();
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         // Act
         CodeTarget.CreateDefault(codeDocument, options, configure: null);
@@ -59,7 +59,7 @@ public void CreateEmpty_AllowsNullDelegate()
     {
         // Arrange
         var codeDocument = TestRazorCodeDocument.CreateEmpty();
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         // Act
         CodeTarget.CreateDefault(codeDocument, options, configure: null);

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

@@ -14,7 +14,7 @@ public void Build_CreatesDefaultCodeTarget()
     {
         // Arrange
         var codeDocument = TestRazorCodeDocument.CreateEmpty();
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var builder = new DefaultCodeTargetBuilder(codeDocument, options);
 

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

@@ -14,7 +14,7 @@ public class DefaultCodeTargetTest
     public void Constructor_CreatesDefensiveCopy()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {
@@ -33,7 +33,7 @@ public void Constructor_CreatesDefensiveCopy()
     public void CreateWriter_DesignTime_CreatesDesignTimeNodeWriter()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDesignTimeDefault();
+        var options = RazorCodeGenerationOptions.DesignTimeDefault;
         var target = new DefaultCodeTarget(options, Enumerable.Empty<ICodeTargetExtension>());
 
         // Act
@@ -47,7 +47,7 @@ public void CreateWriter_DesignTime_CreatesDesignTimeNodeWriter()
     public void CreateWriter_Runtime_CreatesRuntimeNodeWriter()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
         var target = new DefaultCodeTarget(options, Enumerable.Empty<ICodeTargetExtension>());
 
         // Act
@@ -61,7 +61,7 @@ public void CreateWriter_Runtime_CreatesRuntimeNodeWriter()
     public void HasExtension_ReturnsTrue_WhenExtensionFound()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {
@@ -82,7 +82,7 @@ public void HasExtension_ReturnsTrue_WhenExtensionFound()
     public void HasExtension_ReturnsFalse_WhenExtensionNotFound()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {
@@ -103,7 +103,7 @@ public void HasExtension_ReturnsFalse_WhenExtensionNotFound()
     public void GetExtension_ReturnsExtension_WhenExtensionFound()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {
@@ -124,7 +124,7 @@ public void GetExtension_ReturnsExtension_WhenExtensionFound()
     public void GetExtension_ReturnsFirstMatch_WhenExtensionFound()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {
@@ -148,7 +148,7 @@ public void GetExtension_ReturnsFirstMatch_WhenExtensionFound()
     public void GetExtension_ReturnsNull_WhenExtensionNotFound()
     {
         // Arrange
-        var options = RazorCodeGenerationOptions.CreateDefault();
+        var options = RazorCodeGenerationOptions.Default;
 
         var extensions = new ICodeTargetExtension[]
         {