Fix JsonSchemaExporter support for global UnmappedMemberHandling settings. (#107545)

* Fix JsonSchemaExporter support for global UnmappedMemberHandling settings.

* Pass correct parameter in unit test.

Author: eiriktsarpalis

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

@@ -204,7 +204,8 @@ private static JsonSchema MapJsonSchemaCore(
                     List<string>? required = null;
                     JsonSchema? additionalProperties = null;
 
-                    if (typeInfo.UnmappedMemberHandling is JsonUnmappedMemberHandling.Disallow)
+                    JsonUnmappedMemberHandling effectiveUnmappedMemberHandling = typeInfo.UnmappedMemberHandling ?? typeInfo.Options.UnmappedMemberHandling;
+                    if (effectiveUnmappedMemberHandling is JsonUnmappedMemberHandling.Disallow)
                     {
                         additionalProperties = JsonSchema.False;
                     }

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

@@ -677,6 +677,24 @@ public static IEnumerable<ITestData> GetTestDataCore()
                 }
                 """);
 
+            // Global setting for JsonUnmappedMemberHandling.Disallow
+            yield return new TestData<SimplePoco>(
+                Value: new() { String = "string", StringNullable = "string", Int = 42, Double = 3.14, Boolean = true },
+                ExpectedJsonSchema: """
+                {
+                    "type": ["object","null"],
+                    "properties": {
+                        "String": { "type": "string" },
+                        "StringNullable": { "type": ["string", "null"] },
+                        "Int": { "type": "integer" },
+                        "Double": { "type": "number" },
+                        "Boolean": { "type": "boolean" }
+                    },
+                    "additionalProperties": false,
+                }
+                """,
+                SerializerOptions: new() { UnmappedMemberHandling = JsonUnmappedMemberHandling.Disallow });
+
             yield return new TestData<PocoWithNullableAnnotationAttributes>(
                 Value: new() { MaybeNull = null!, AllowNull = null, NotNull = null, DisallowNull = null!, NotNullDisallowNull = "str" },
                 ExpectedJsonSchema: """
@@ -1446,7 +1464,8 @@ public record TestData<T>(
             T? Value,
             string ExpectedJsonSchema,
             IEnumerable<T?>? AdditionalValues = null,
-            JsonSchemaExporterOptions? Options = null)
+            JsonSchemaExporterOptions? Options = null,
+            JsonSerializerOptions? SerializerOptions = null)
             : ITestData
         {
             public Type Type => typeof(T);
@@ -1481,6 +1500,8 @@ public interface ITestData
 
             JsonSchemaExporterOptions? Options { get; }
 
+            JsonSerializerOptions? SerializerOptions { get; }
+
             IEnumerable<ITestData> GetTestDataForAllValues();
         }
 

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

@@ -29,16 +29,24 @@ protected JsonSchemaExporterTests(JsonSerializerWrapper serializer) : base(seria
         [ActiveIssue("https://github.com/dotnet/runtime/issues/103694", TestRuntimes.Mono)]
         public void TestTypes_GeneratesExpectedJsonSchema(ITestData testData)
         {
-            JsonNode schema = Serializer.DefaultOptions.GetJsonSchemaAsNode(testData.Type, testData.Options);
+            JsonSerializerOptions options = testData.SerializerOptions is { } opts
+                ? new(opts) { TypeInfoResolver = Serializer.DefaultOptions.TypeInfoResolver }
+                : Serializer.DefaultOptions;
+
+            JsonNode schema = options.GetJsonSchemaAsNode(testData.Type, testData.Options);
             AssertValidJsonSchema(testData.Type, testData.ExpectedJsonSchema, schema);
         }
 
         [Theory]
         [MemberData(nameof(GetTestDataUsingAllValues))]
         public void TestTypes_SerializedValueMatchesGeneratedSchema(ITestData testData)
         {
-            JsonNode schema = Serializer.DefaultOptions.GetJsonSchemaAsNode(testData.Type, testData.Options);
-            JsonNode? instance = JsonSerializer.SerializeToNode(testData.Value, testData.Type, Serializer.DefaultOptions);
+            JsonSerializerOptions options = testData.SerializerOptions is { } opts
+                ? new(opts) { TypeInfoResolver = Serializer.DefaultOptions.TypeInfoResolver }
+                : Serializer.DefaultOptions;
+
+            JsonNode schema = options.GetJsonSchemaAsNode(testData.Type, testData.Options);
+            JsonNode? instance = JsonSerializer.SerializeToNode(testData.Value, testData.Type, options);
             AssertDocumentMatchesSchema(schema, instance);
         }