fix/additional properties false to v3

CHANGELOG.md

@@ -2,14 +2,12 @@
 
 ## [3.1.0](https://github.com/microsoft/OpenAPI.NET/compare/v3.0.3...v3.1.0) (2025-12-17)
 
-
 ### Features
 
 * Add `type: "null"` downcasting when in oneOf and anyOf for OpenAPI v3 ([782cf8d](https://github.com/microsoft/OpenAPI.NET/commit/782cf8d1ff8166e3c7be706e08dabf168b9616a4))
 
 ## [3.0.3](https://github.com/microsoft/OpenAPI.NET/compare/v3.0.2...v3.0.3) (2025-12-16)
 
-### Bug Fixes
 
 * load JSON documents that are preceded by multiple whitespace ([6461bac](https://github.com/microsoft/OpenAPI.NET/commit/6461bac01c4176424210e9ac249698f665a514a6))
 * non-seekable json streams would fail to load as a document ([2436d73](https://github.com/microsoft/OpenAPI.NET/commit/2436d7382bfbf8b9ba501d88f682e952bdf27146))
@@ -43,8 +41,20 @@
 
 * adds support for OpenAPI 3.2.0 ([765a8dd](https://github.com/microsoft/OpenAPI.NET/commit/765a8dd4d6efd1a31b6a76d282ccffa5877a845a))
 
-## [2.3.12](https://github.com/microsoft/OpenAPI.NET/compare/v2.3.11...v2.3.12) (2025-12-15)
+## [2.4.1](https://github.com/microsoft/OpenAPI.NET/compare/v2.4.0...v2.4.1) (2025-12-18)
+
+### Bug Fixes
+
+* **schema:** always serialize `additionalProperties: false` ([6651c36](https://github.com/microsoft/OpenAPI.NET/commit/6651c36ff341329c053776d65b36b1b7fa9dd3ea))
+* **schema:** always serialize `additionalProperties: false` ([e36fc95](https://github.com/microsoft/OpenAPI.NET/commit/e36fc9565bce42916eb7bf64d1f74d491dd1f407))
 
+## [2.4.0](https://github.com/microsoft/OpenAPI.NET/compare/v2.3.12...v2.4.0) (2025-12-17)
+
+### Features
+
+* Add `type: "null"` downcasting when in oneOf and anyOf for OpenAPI v3 ([782cf8d](https://github.com/microsoft/OpenAPI.NET/commit/782cf8d1ff8166e3c7be706e08dabf168b9616a4))
+
+## [2.3.12](https://github.com/microsoft/OpenAPI.NET/compare/v2.3.11...v2.3.12) (2025-12-15)
 
 ### Bug Fixes
 

src/Microsoft.OpenApi/Models/OpenApiSchema.cs

@@ -264,7 +264,7 @@
         /// Initializes a copy of <see cref="IOpenApiSchema"/> object
         /// </summary>
         /// <param name="schema">The schema object to copy from.</param>
         internal OpenApiSchema(IOpenApiSchema schema)
         {
             Utils.CheckArgumentNull(schema);
             Title = schema.Title ?? Title;
@@ -341,23 +341,23 @@
             SerializeInternal(writer, OpenApiSpecVersion.OpenApi3_0, (writer, element) => element.SerializeAsV3(writer));
         }
 
         private static void SerializeBounds(IOpenApiWriter writer, OpenApiSpecVersion version, string propertyName, string exclusivePropertyName, string isExclusivePropertyName, string? value, string? exclusiveValue, bool? isExclusiveValue)
         {
             if (version >= OpenApiSpecVersion.OpenApi3_1)
             {
                 if (!string.IsNullOrEmpty(exclusiveValue) && exclusiveValue is not null)
                 {
                     // was explicitly set in the document or object model
                     writer.WritePropertyName(exclusivePropertyName);
                     writer.WriteRaw(exclusiveValue);
                 }
                 else if (isExclusiveValue == true && !string.IsNullOrEmpty(value) && value is not null)
                 {
                     // came from parsing an old document
                     writer.WritePropertyName(exclusivePropertyName);
                     writer.WriteRaw(value);
                 }
                 else if (!string.IsNullOrEmpty(value) && value is not null)
                 {
                     // was explicitly set in the document or object model
                     writer.WritePropertyName(propertyName);
@@ -366,14 +366,14 @@
             }
             else
             {
                 if (!string.IsNullOrEmpty(exclusiveValue) && exclusiveValue is not null)
                 {
                     // was explicitly set in a new document being downcast or object model
                     writer.WritePropertyName(propertyName);
                     writer.WriteRaw(exclusiveValue);
                     writer.WriteProperty(isExclusivePropertyName, true);
                 }
                 else if (!string.IsNullOrEmpty(value) && value is not null)
                 {
                     // came from parsing an old document, we're just mirroring the information
                     writer.WritePropertyName(propertyName);
@@ -435,7 +435,7 @@
             // required
             writer.WriteOptionalCollection(OpenApiConstants.Required, Required, (w, s) =>
             {
                 if (!string.IsNullOrEmpty(s) && s is not null)
                 {
                     w.WriteValue(s);
                 }
@@ -494,9 +494,8 @@
                     AdditionalProperties,
                     callback);
             }
-            // true is the default in earlier versions 3, no need to write it out
-            // boolean value is only supported for version 3 and earlier (version 2 is implemented in the other serialize method, the condition is a failsafe)
-            else if (!AdditionalPropertiesAllowed && version <= OpenApiSpecVersion.OpenApi3_0)
+            // true is the default, no need to write it out
+            else if (!AdditionalPropertiesAllowed)
             {
                 writer.WriteProperty(OpenApiConstants.AdditionalProperties, AdditionalPropertiesAllowed);
             }

test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs

@@ -755,8 +755,11 @@ public async Task SerializeAdditionalPropertiesAllowedAsV3PlusDefaultDoesNotEmit
             Assert.True(JsonNode.DeepEquals(JsonNode.Parse(expected), JsonNode.Parse(actual)));
         }
 
-        [Fact]
-        public async Task SerializeAdditionalPropertiesAllowedAsV3FalseEmits()
+        [Theory]
+        [InlineData(OpenApiSpecVersion.OpenApi3_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_1)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_2)]
+        public async Task SerializeAdditionalPropertiesAllowedAsV3PlusFalseEmits(OpenApiSpecVersion version)
         {
             var expected = @"{ ""additionalProperties"": false }";
             // Given
@@ -766,7 +769,7 @@ public async Task SerializeAdditionalPropertiesAllowedAsV3FalseEmits()
             };
 
             // When
-            var actual = await schema.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_0);
+            var actual = await schema.SerializeAsJsonAsync(version);
 
             // Then
             Assert.True(JsonNode.DeepEquals(JsonNode.Parse(expected), JsonNode.Parse(actual)));