Clean up JSON source gen APIs (dotnet#54527)

* Clean up JSON source gen APIs

* Address review feedback

* Simplify GenerateX computation

src/libraries/System.Text.Json/Common/JsonKnownNamingPolicy.cs

@@ -21,6 +21,6 @@ enum JsonKnownNamingPolicy
         /// <summary>
         /// Specifies that the built-in <see cref="Json.JsonNamingPolicy.CamelCase"/> be used to convert JSON property names.
         /// </summary>
-        BuiltInCamelCase = 1
+        CamelCase = 1
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Attributes/JsonSerializableAttribute.cs → src/libraries/System.Text.Json/Common/JsonSerializableAttribute.cs

@@ -1,7 +1,9 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+#if !BUILDING_SOURCE_GENERATOR
 using System.Text.Json.Serialization.Metadata;
+#endif
 
 namespace System.Text.Json.Serialization
 {
@@ -10,7 +12,13 @@ namespace System.Text.Json.Serialization
     /// when serializing and deserializing instances of the specified type and types in its object graph.
     /// </summary>
     [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
-    public sealed class JsonSerializableAttribute : JsonAttribute
+
+#if BUILDING_SOURCE_GENERATOR
+    internal
+#else
+    public
+#endif
+    sealed class JsonSerializableAttribute : JsonAttribute
     {
         /// <summary>
         /// Initializes a new instance of <see cref="JsonSerializableAttribute"/> with the specified type.
@@ -28,7 +36,8 @@ public JsonSerializableAttribute(Type type) { }
         public string? TypeInfoPropertyName { get; set; }
 
         /// <summary>
-        /// Determines what the source generator should generate for the type.
+        /// Determines what the source generator should generate for the type. If the value is <see cref="JsonSourceGenerationMode.Default"/>,
+        /// then the setting specified on <see cref="JsonSourceGenerationOptionsAttribute.GenerationMode"/> will be used.
         /// </summary>
         public JsonSourceGenerationMode GenerationMode { get; set; }
     }

src/libraries/System.Text.Json/Common/JsonSourceGenerationMode.cs

@@ -15,13 +15,11 @@ namespace System.Text.Json.Serialization
     enum JsonSourceGenerationMode
     {
         /// <summary>
-        /// Instructs the JSON source generator to generate serialization logic and type metadata to fallback to
-        /// when the run-time options are not compatible with the indicated <see cref="JsonSerializerOptionsAttribute"/>.
+        /// When specified on <see cref="JsonSourceGenerationOptionsAttribute.GenerationMode"/>, indicates that both type-metadata initialization logic
+        /// and optimized serialization logic should be generated for all types. When specified on <see cref="JsonSerializableAttribute.GenerationMode"/>,
+        /// indicates that the setting on <see cref="JsonSourceGenerationOptionsAttribute.GenerationMode"/> should be used.
         /// </summary>
-        /// <remarks>
-        /// This mode supports all <see cref="JsonSerializer"/> features.
-        /// </remarks>
-        MetadataAndSerialization = 0,
+        Default = 0,
 
         /// <summary>
         /// Instructs the JSON source generator to generate type-metadata initialization logic.
@@ -32,7 +30,7 @@ enum JsonSourceGenerationMode
         Metadata = 1,
 
         /// <summary>
-        /// Instructs the JSON source generator to generate serialization logic.
+        /// Instructs the JSON source generator to generate optimized serialization logic.
         /// </summary>
         /// <remarks>
         /// This mode supports only a subset of <see cref="JsonSerializer"/> features.

src/libraries/System.Text.Json/Common/JsonSerializerOptionsAttribute.cs → src/libraries/System.Text.Json/Common/JsonSourceGenerationOptionsAttribute.cs

@@ -13,7 +13,7 @@ namespace System.Text.Json.Serialization
 #else
     public
 #endif
-    class JsonSerializerOptionsAttribute : JsonAttribute
+    class JsonSourceGenerationOptionsAttribute : JsonAttribute
     {
         /// <summary>
         /// Specifies the default ignore condition.
@@ -43,11 +43,16 @@ class JsonSerializerOptionsAttribute : JsonAttribute
         /// <summary>
         /// Specifies a built-in naming polices to convert JSON property names with.
         /// </summary>
-        public JsonKnownNamingPolicy NamingPolicy { get; set; }
+        public JsonKnownNamingPolicy PropertyNamingPolicy { get; set; }
 
         /// <summary>
         /// Specifies whether JSON output should be pretty-printed.
         /// </summary>
         public bool WriteIndented { get; set; }
+
+        /// <summary>
+        /// Specifies the source generation mode for types that don't explicitly set the mode with <see cref="JsonSerializableAttribute.GenerationMode"/>.
+        /// </summary>
+        public JsonSourceGenerationMode GenerationMode { get; set; }
     }
 }

src/libraries/System.Text.Json/gen/ContextGenerationSpec.cs

@@ -13,11 +13,11 @@ namespace System.Text.Json.SourceGeneration
     /// </summary>
     internal sealed class ContextGenerationSpec
     {
-        public JsonSerializerOptionsAttribute SerializerOptions { get; init; }
+        public JsonSourceGenerationOptionsAttribute GenerationOptions { get; init; }
 
         public Type ContextType { get; init; }
 
-        public List<TypeGenerationSpec>? RootSerializableTypes { get; init; }
+        public List<TypeGenerationSpec> RootSerializableTypes { get; } = new();
 
         public List<string> ContextClassDeclarationList { get; init; }
 

src/libraries/System.Text.Json/gen/JsonSourceGenerator.Emitter.cs

@@ -637,10 +637,10 @@ private string GenerateFastPathFuncForObject(
                 bool canBeNull,
                 List<PropertyGenerationSpec>? properties)
             {
-                JsonSerializerOptionsAttribute options = _currentContext.SerializerOptions;
+                JsonSourceGenerationOptionsAttribute options = _currentContext.GenerationOptions;
 
                 // Add the property names to the context-wide cache; we'll generate the source to initialize them at the end of generation.
-                string[] runtimePropNames = GetRuntimePropNames(properties, options.NamingPolicy);
+                string[] runtimePropNames = GetRuntimePropNames(properties, options.PropertyNamingPolicy);
                 _currentContext.RuntimePropertyNames.UnionWith(runtimePropNames);
 
                 StringBuilder sb = new();
@@ -855,7 +855,7 @@ private string DetermineRuntimePropName(string clrPropName, string? jsonPropName
                 {
                     runtimePropName = jsonPropName;
                 }
-                else if (namingPolicy == JsonKnownNamingPolicy.BuiltInCamelCase)
+                else if (namingPolicy == JsonKnownNamingPolicy.CamelCase)
                 {
                     runtimePropName = JsonNamingPolicy.CamelCase.ConvertName(clrPropName);
                 }
@@ -890,7 +890,7 @@ private string GenerateForType(TypeGenerationSpec typeMetadata, string metadataI
 
             private string WrapWithCheckForCustomConverterIfRequired(string source, string typeCompilableName, string typeFriendlyName, string numberHandlingNamedArg)
             {
-                if (_currentContext.SerializerOptions.IgnoreRuntimeCustomConverters)
+                if (_currentContext.GenerationOptions.IgnoreRuntimeCustomConverters)
                 {
                     return source;
                 }
@@ -933,9 +933,9 @@ private string GetRootJsonContextImplementation()
 
             private string GetLogicForDefaultSerializerOptionsInit()
             {
-                JsonSerializerOptionsAttribute options = _currentContext.SerializerOptions;
+                JsonSourceGenerationOptionsAttribute options = _currentContext.GenerationOptions;
 
-                string? namingPolicyInit = options.NamingPolicy == JsonKnownNamingPolicy.BuiltInCamelCase
+                string? namingPolicyInit = options.PropertyNamingPolicy == JsonKnownNamingPolicy.CamelCase
                     ? $@"
             PropertyNamingPolicy = {JsonNamingPolicyTypeRef}.CamelCase"
                     : null;
@@ -953,7 +953,7 @@ private string GetLogicForDefaultSerializerOptionsInit()
 
             private string GetFetchLogicForRuntimeSpecifiedCustomConverter()
             {
-                if (_currentContext.SerializerOptions.IgnoreRuntimeCustomConverters)
+                if (_currentContext.GenerationOptions.IgnoreRuntimeCustomConverters)
                 {
                     return "";
                 }