Make CharacterReader internal. (#19123)

* Make `CharacterReader` internal.

And by extension, make the static classes which define extension methods on it internal.

To do this, I had to make Avalonia.Base's internals visible to Avalonia.Designer.HostApp, as that has a dependency on it, and exclude `StringCompatibilityExtensions` from there as the one from Avalonia.Base is now visible.

* Don't expose internals to HostApp.

Exposing Avalonia.Base's internals to Avalonia.Designer.HostApp caused an issue with the dependency on `StringCompatibilityExtensions` - because the hostapp is loaded into the target app and `StringCompatibilityExtensions` is conditionally compiled, you ended up with it being loaded into an app which does not have `StringCompatibilityExtensions`.

Instead, add `string` overloads of the internal APIs which take a `CharacterReader` so that they can be called even when `CharacterReader` isn't available.

* Update API diff.

api/Avalonia.nupkg.xml

@@ -7,6 +7,30 @@
     <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
     <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Utilities.CharacterReader</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Utilities.IdentifierParser</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Utilities.KeywordParser</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Utilities.StyleClassParser</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Avalonia.Diagnostics.AppliedStyle.get_HasActivator</Target>

src/Avalonia.Base/Utilities/CharacterReader.cs

@@ -2,11 +2,7 @@ using System;
 
 namespace Avalonia.Utilities
 {
-    // TODO12: This should not be public
-#if !BUILDTASK
-    public
-#endif
-    ref struct CharacterReader
+    internal ref struct CharacterReader
     {
         private ReadOnlySpan<char> _s;
 

src/Avalonia.Base/Utilities/IdentifierParser.cs

@@ -3,10 +3,7 @@ using System.Globalization;
 
 namespace Avalonia.Utilities
 {
-#if !BUILDTASK
-    public
-#endif
-    static class IdentifierParser
+    internal static class IdentifierParser
     {
         public static ReadOnlySpan<char> ParseIdentifier(this
 #if NET7SDK

src/Avalonia.Base/Utilities/KeywordParser.cs

@@ -2,10 +2,7 @@ using System;
 
 namespace Avalonia.Utilities
 {
-#if !BUILDTASK
-    public
-#endif
-    static class KeywordParser
+    internal static class KeywordParser
     {
         public static bool CheckKeyword(this ref CharacterReader r, string keyword)
         {

src/Avalonia.Base/Utilities/StyleClassParser.cs

@@ -3,10 +3,7 @@ using System.Globalization;
 
 namespace Avalonia.Utilities
 {
-#if !BUILDTASK
-    public
-#endif
-    static class StyleClassParser
+    internal static class StyleClassParser
     {
         public static ReadOnlySpan<char> ParseStyleClass(this ref CharacterReader r)
         {

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlBindingPathParser.cs

@@ -22,8 +22,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
 
                 if (binding.Arguments.Count > 0 && binding.Arguments[0] is XamlAstTextNode bindingPathText)
                 {
-                    var reader = new CharacterReader(bindingPathText.Text.AsSpan());
-                    var (nodes, _) = BindingExpressionGrammar.Parse(ref reader);
+                    var (nodes, _) = BindingExpressionGrammar.Parse(bindingPathText.Text);
 
                     if (convertedNode != null)
                     {
@@ -48,8 +47,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
 
                     if (bindingPathAssignment != null && bindingPathAssignment.Values[0] is XamlAstTextNode pathValue)
                     {
-                        var reader = new CharacterReader(pathValue.Text.AsSpan());
-                        var (nodes, _) = BindingExpressionGrammar.Parse(ref reader);
+                        var (nodes, _) = BindingExpressionGrammar.Parse(pathValue.Text);
 
                         if (nodes.Count == 1 && nodes[0] is BindingExpressionGrammar.EmptyExpressionNode)
                         {

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlAvaloniaPropertyHelper.cs

@@ -64,7 +64,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
         {
             XamlAstNamePropertyReference forgedReference;
 
-            var parsedPropertyName = PropertyParser.Parse(new CharacterReader(propertyName.AsSpan()));
+            var parsedPropertyName = PropertyParser.Parse(propertyName);
             if(parsedPropertyName.owner == null)
                 forgedReference = new XamlAstNamePropertyReference(lineInfo, selectorTypeReference,
                     propertyName, selectorTypeReference);

src/Markup/Avalonia.Markup.Xaml/Parsers/PropertyParser.cs

@@ -1,10 +1,17 @@
-using Avalonia.Data.Core;
+using System;
+using Avalonia.Data.Core;
 using Avalonia.Utilities;
 
 namespace Avalonia.Markup.Xaml.Parsers
 {
     internal class PropertyParser
     {
+        public static (string? ns, string? owner, string name) Parse(string text)
+        {
+            var r = new CharacterReader(text.AsSpan());
+            return Parse(r);
+        }
+
         public static (string? ns, string? owner, string name) Parse(CharacterReader r)
         {
             if (r.End)

src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs

@@ -1,10 +1,10 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
-using Avalonia.Data.Core;
-using Avalonia.Utilities;
 using System;
 using System.Collections.Generic;
+using Avalonia.Data.Core;
+using Avalonia.Utilities;
 
 namespace Avalonia.Markup.Parsers
 {
@@ -18,6 +18,12 @@ namespace Avalonia.Markup.Parsers
     {
         private static readonly List<INode> s_pool = new();
 
+        public static (List<INode> Nodes, SourceMode Mode) Parse(string text)
+        {
+            var r = new CharacterReader(text.AsSpan());
+            return Parse(ref r);
+        }
+
         public static (List<INode> Nodes, SourceMode Mode) Parse(ref CharacterReader r)
         {
             var result = new List<INode>();