Fix transformer handling of boolean schemas in JsonSchemaExporter. (dotnet#109954)

* Fix transformer handling of boolean schemas in JsonSchemaExporter.

* Address feedback.

Author: eiriktsarpalis

src/libraries/System.Text.Json/src/System/Text/Json/Schema/JsonSchema.cs

@@ -26,8 +26,8 @@ internal sealed class JsonSchema
         internal const string MinLengthPropertyName = "minLength";
         internal const string MaxLengthPropertyName = "maxLength";
 
-        public static JsonSchema False { get; } = new(false);
-        public static JsonSchema True { get; } = new(true);
+        public static JsonSchema CreateFalseSchema() => new(false);
+        public static JsonSchema CreateTrueSchema() => new(true);
 
         public JsonSchema() { }
         private JsonSchema(bool trueOrFalse) { _trueOrFalse = trueOrFalse; }
@@ -279,7 +279,7 @@ public static void EnsureMutable(ref JsonSchema schema)
             switch (schema._trueOrFalse)
             {
                 case false:
-                    schema = new JsonSchema { Not = True };
+                    schema = new JsonSchema { Not = CreateTrueSchema() };
                     break;
                 case true:
                     schema = new JsonSchema();

src/libraries/System.Text.Json/src/System/Text/Json/Schema/JsonSchemaExporter.cs

@@ -211,7 +211,7 @@ private static JsonSchema MapJsonSchemaCore(
                     JsonUnmappedMemberHandling effectiveUnmappedMemberHandling = typeInfo.UnmappedMemberHandling ?? typeInfo.Options.UnmappedMemberHandling;
                     if (effectiveUnmappedMemberHandling is JsonUnmappedMemberHandling.Disallow)
                     {
-                        additionalProperties = JsonSchema.False;
+                        additionalProperties = JsonSchema.CreateFalseSchema();
                     }
 
                     if (typeDiscriminator is { } typeDiscriminatorPair)
@@ -350,7 +350,7 @@ private static JsonSchema MapJsonSchemaCore(
                 default:
                     Debug.Assert(typeInfo.Kind is JsonTypeInfoKind.None);
                     // Return a `true` schema for types with user-defined converters.
-                    return CompleteSchema(ref state, JsonSchema.True);
+                    return CompleteSchema(ref state, JsonSchema.CreateTrueSchema());
             }
 
             JsonSchema CompleteSchema(ref GenerationState state, JsonSchema schema)

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Node/JsonNodeConverter.cs

@@ -80,6 +80,6 @@ public override void Write(Utf8JsonWriter writer, JsonNode? value, JsonSerialize
             return node;
         }
 
-        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.True;
+        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.CreateTrueSchema();
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Node/JsonValueConverter.cs

@@ -31,6 +31,6 @@ public override void Write(Utf8JsonWriter writer, JsonValue? value, JsonSerializ
             return JsonValue.CreateFromElement(ref element, options.GetNodeOptions());
         }
 
-        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.True;
+        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.CreateTrueSchema();
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectConverter.cs

@@ -147,6 +147,6 @@ internal override bool OnTryRead(ref Utf8JsonReader reader, Type typeToConvert,
             return true;
         }
 
-        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.True;
+        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.CreateTrueSchema();
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/JsonDocumentConverter.cs

@@ -26,6 +26,6 @@ public override void Write(Utf8JsonWriter writer, JsonDocument? value, JsonSeria
             value.WriteTo(writer);
         }
 
-        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.True;
+        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.CreateTrueSchema();
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/JsonElementConverter.cs

@@ -18,6 +18,6 @@ public override void Write(Utf8JsonWriter writer, JsonElement value, JsonSeriali
             value.WriteTo(writer);
         }
 
-        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.True;
+        internal override JsonSchema? GetSchema(JsonNumberHandling _) => JsonSchema.CreateTrueSchema();
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/UnsupportedTypeConverter.cs

@@ -21,6 +21,6 @@ public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions
             throw new NotSupportedException(ErrorMessage);
 
         internal override JsonSchema? GetSchema(JsonNumberHandling _) =>
-            new JsonSchema { Comment = "Unsupported .NET type", Not = JsonSchema.True };
+            new JsonSchema { Comment = "Unsupported .NET type", Not = JsonSchema.CreateTrueSchema() };
     }
 }

src/libraries/System.Text.Json/tests/Common/JsonSchemaExporterTests.TestTypes.cs

@@ -1102,6 +1102,18 @@ of the type which points to the first occurrence. */
                         }
                         """);
 
+            yield return new TestData<ClassWithPropertiesUsingCustomConverters>(
+                Value: new() { Prop1 = new() , Prop2 = new() },
+                ExpectedJsonSchema: """
+                    {
+                        "type": ["object","null"],
+                        "properties": {
+                          "Prop1": true,
+                          "Prop2": true,
+                        }
+                    }
+                    """);
+
             // Collection types
             yield return new TestData<int[]>([1, 2, 3], ExpectedJsonSchema: """{"type":["array","null"],"items":{"type":"integer"}}""");
             yield return new TestData<List<bool>>([false, true, false], ExpectedJsonSchema: """{"type":["array","null"],"items":{"type":"boolean"}}""");
@@ -1586,6 +1598,29 @@ public interface ITestData
             IEnumerable<ITestData> GetTestDataForAllValues();
         }
 
+        public class ClassWithPropertiesUsingCustomConverters
+        {
+            [JsonPropertyOrder(0)]
+            public ClassWithCustomConverter1 Prop1 { get; set; }
+            [JsonPropertyOrder(1)]
+            public ClassWithCustomConverter2 Prop2 { get; set; }
+
+            [JsonConverter(typeof(CustomConverter<ClassWithCustomConverter1>))]
+            public class ClassWithCustomConverter1;
+
+            [JsonConverter(typeof(CustomConverter<ClassWithCustomConverter2>))]
+            public class ClassWithCustomConverter2;
+
+            public sealed class CustomConverter<T> : JsonConverter<T>
+            {
+                public override T? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+                    => default;
+
+                public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+                    => writer.WriteNullValue();
+            }
+        }
+
         private static TAttribute? GetCustomAttribute<TAttribute>(ICustomAttributeProvider? provider, bool inherit = false) where TAttribute : Attribute
             => provider?.GetCustomAttributes(typeof(TAttribute), inherit).FirstOrDefault() as TAttribute;
     }

src/libraries/System.Text.Json/tests/Common/JsonSchemaExporterTests.cs

@@ -98,6 +98,32 @@ public void CanGenerateXElementSchema()
             Assert.True(schema.ToJsonString().Length < 100_000);
         }
 
+        [Fact]
+        public void TransformSchemaNode_PropertiesWithCustomConverters()
+        {
+            // Regression test for https://github.com/dotnet/runtime/issues/109868
+            List<(Type? ParentType, string? PropertyName, Type type)> visitedNodes = new();
+            JsonSchemaExporterOptions exporterOptions = new()
+            {
+                TransformSchemaNode = (ctx, schema) =>
+                {
+                    visitedNodes.Add((ctx.PropertyInfo?.DeclaringType, ctx.PropertyInfo?.Name, ctx.TypeInfo.Type));
+                    return schema;
+                }
+            };
+
+            List<(Type? ParentType, string? PropertyName, Type type)> expectedNodes =
+            [
+                (typeof(ClassWithPropertiesUsingCustomConverters), "Prop1", typeof(ClassWithPropertiesUsingCustomConverters.ClassWithCustomConverter1)),
+                (typeof(ClassWithPropertiesUsingCustomConverters), "Prop2", typeof(ClassWithPropertiesUsingCustomConverters.ClassWithCustomConverter2)),
+                (null, null, typeof(ClassWithPropertiesUsingCustomConverters)),
+            ];
+
+            Serializer.DefaultOptions.GetJsonSchemaAsNode(typeof(ClassWithPropertiesUsingCustomConverters), exporterOptions);
+
+            Assert.Equal(expectedNodes, visitedNodes);
+        }
+
         [Fact]
         public void TypeWithDisallowUnmappedMembers_AdditionalPropertiesFailValidation()
         {