Handle nullable types in OpenAPI schemas and add corresponding unit t… by X39 · Pull Request #7170 · microsoft/kiota

X39 · 2025-11-28T02:00:48Z

This commit provides a basic fix for #6776, unblocking nullable reference types for ASP.Net Core.

It also, magically (aka: as a side effect), makes enums work

X39 · 2025-11-28T02:12:49Z

@microsoft-github-policy-service agree

…nit tests. This commit provides a basic fix for microsoft#6776, unblocking nullable reference types for ASP.Net Core.

lvde0 · 2025-12-10T10:36:03Z

@gavinbarron Could you have a look at this?

snerte · 2025-12-11T08:14:16Z

Please fix this issue

X39 · 2025-12-11T09:43:20Z

Just to note for those in dire need of a fix: building kiota on your own is trivial, after that, just refer to the built version, rather than the installed one by path (aka the .../kiota/bin/release/kiota.exe one)

That is what I am doing right now

StefanOverHaevgRZ · 2025-12-16T10:09:55Z

@baywet What do we need to get this merged?

baywet · 2025-12-16T17:12:05Z

I have transitioned to a new team back in August 2025 and won't be replying to this issue/pull request moving forward.
Thank you for your understanding.

@gavinbarron and @adrian05-ms to take over

gavinbarron

Thank you so much for this contribution.

There are a few areas that are untested and need coverage so that we can get this shippable.

tests/Kiota.Builder.Tests/Writers/CSharp/YamlToCSharpTests.cs

src/Kiota.Builder/Extensions/OpenApiSchemaExtensions.cs

gavinbarron · 2026-01-23T18:19:13Z

src/Kiota.Builder/Writers/CSharp/CodeMethodWriter.cs

+            var serializationMethodName = GetSerializationMethodName(otherProp.Type, method);
            writer.WriteLine($"{(includeElse ? "else " : string.Empty)}if({otherProp.Name.ToFirstCharacterUpperCase()} != null)");
-            writer.WriteBlock(lines: $"writer.{GetSerializationMethodName(otherProp.Type, method)}(null, {otherProp.Name.ToFirstCharacterUpperCase()});");
+            if (otherProp.Type is CodeType{TypeDefinition: CodeEnum {BackingType: JsonSchemaType.Integer}})


I'm not seeing any tests for serialization of union models that include Integer Enums, let's make sure test cases for this are added.

It feels a bit weird that the integer case is passing otherProp.WireName which is inconsistent with how the existing case works.

I am very aware of that, wanted to avoid cross-repository changes tho and have this easily integrateable on my end.

Could you hint me at where those tests are currently placed and how they look? Thanks in advance.

Here's where we have an existing test for the union model serialization

kiota/tests/Kiota.Builder.Tests/Writers/CSharp/CodeMethodWriterTests.cs

Line 1394 in 2848c0b

public void WritesUnionDeSerializerBody()

It focuses on the code that is generated, rather than the behavior of the serialization library that we have as a dependency.

gavinbarron · 2026-01-23T18:19:37Z

src/Kiota.Builder/Writers/CSharp/CodeMethodWriter.cs

+            var serializationMethodName = GetSerializationMethodName(otherProp.Type, method);
            writer.WriteLine($"{(includeElse ? "else " : string.Empty)}if({otherProp.Name.ToFirstCharacterUpperCase()} != null)");
-            writer.WriteBlock(lines: $"writer.{GetSerializationMethodName(otherProp.Type, method)}(null, {otherProp.Name.ToFirstCharacterUpperCase()});");
+            if (otherProp.Type is CodeType{TypeDefinition: CodeEnum {BackingType: JsonSchemaType.Integer}})


I'm not seeing any tests for serialization of intersection models that include Integer Enums, let's make sure test cases for this are added.

I am not entirely sure what you mean by that, could you provide a sample json?
Also, where are those tests currently located at?

Thanks in advance

Here's the existing test for generating the serialization method

kiota/tests/Kiota.Builder.Tests/Writers/CSharp/CodeMethodWriterTests.cs

Line 1419 in 2848c0b

public void WritesIntersectionDeSerializerBody()

I have supplied sample open api for these types of schema on the factory method/deserialization comments

gavinbarron · 2026-01-23T18:26:51Z

src/Kiota.Builder/Writers/CSharp/CodeMethodWriter.cs

                    var valueVarName = $"{property.Name.ToFirstCharacterLowerCase()}Value";
-                    writer.WriteLine($"{(includeElse ? "else " : string.Empty)}if({parseNodeParameter.Name.ToFirstCharacterLowerCase()}.{GetDeserializationMethodName(propertyType, codeElement)} is {typeName} {valueVarName})");
-                    writer.WriteBlock(lines: $"{ResultVarName}.{property.Name.ToFirstCharacterUpperCase()} = {valueVarName};");
+                    if (propertyType.TypeDefinition is CodeType { TypeDefinition: CodeEnum {BackingType: JsonSchemaType.Integer}})


This need test coverage to ensure the deserialization code is generated correctly for the case of a union model with an integer enum.

I am not entirely sure what you mean by that, could you provide a sample json?
Also, where are those tests currently located at?

Thanks in advance

Here's where the tests for this method start:

kiota/tests/Kiota.Builder.Tests/Writers/CSharp/CodeMethodWriterTests.cs

Line 592 in 2848c0b

public void WritesModelFactoryBodyForUnionModels()

A union model with and integer enum might looks something like:

openapi: 3.0.3 info: title: Union with Integer Enum API version: 1.0.0 servers: - url: https://api.example.com/v1 paths: /status: get: summary: Get status that can be multiple types responses: '200': description: A union type containing an integer enum content: application/json: schema: $ref: '#/components/schemas/StatusUnion' components: schemas: # Integer-backed enum StatusEnum: type: integer enum: [0, 1, 2] x-ms-enum: name: StatusEnum modelAsString: false values: - name: Active value: 0 description: "The resource is active" - name: Inactive value: 1 description: "The resource is inactive" - name: Pending value: 2 description: "The resource is pending" # A complex object type DetailedStatus: type: object required: - message properties: message: type: string code: type: integer # Union model combining integer enum and object StatusUnion: oneOf: - $ref: '#/components/schemas/StatusEnum' - $ref: '#/components/schemas/DetailedStatus' discriminator: propertyName: '@odata.type' mapping: '#kiota.statusEnum': '#/components/schemas/StatusEnum' '#kiota.detailedStatus': '#/components/schemas/DetailedStatus'

gavinbarron · 2026-01-23T18:27:11Z

src/Kiota.Builder/Writers/CSharp/CodeMethodWriter.cs

                var valueVarName = $"{property.Name.ToFirstCharacterLowerCase()}Value";
-                writer.WriteLine($"{(includeElse ? "else " : string.Empty)}if({parseNodeParameter.Name.ToFirstCharacterLowerCase()}.{GetDeserializationMethodName(propertyType, codeElement)} is {typeName} {valueVarName})");
-                writer.WriteBlock(lines: $"{ResultVarName}.{property.Name.ToFirstCharacterUpperCase()} = {valueVarName};");
+                if (propertyType.TypeDefinition is CodeType { TypeDefinition: CodeEnum {BackingType: JsonSchemaType.Integer}})


This need test coverage to ensure the deserialization code is generated correctly for the case of a intersection model with an integer enum.

I am not entirely sure what you mean by that, could you provide a sample json?
Also, where are those tests currently located at?

Thanks in advance

Intersection model tests start here:

kiota/tests/Kiota.Builder.Tests/Writers/CSharp/CodeMethodWriterTests.cs

Line 891 in 2848c0b

public void WritesModelFactoryBodyForIntersectionModels()

Example of an intersection model based on the previous union model example

StatusIntersection: allOf: - $ref: '#/components/schemas/StatusEnum' - $ref: '#/components/schemas/DetailedStatus'

Theese cover what is discussed in microsoft#7170 (comment)

This test covers the requested changes, requested in https://github.com/microsoft/kiota/pull/7170/changes/BASE..592710aa6905adea20c73192cf204a3b6f83f2fa#r2722212419

X39 requested a review from a team as a code owner November 28, 2025 02:00

X39 marked this pull request as draft November 29, 2025 13:18

X39 added 2 commits November 29, 2025 16:21

fix: Handle nullable types in OpenAPI schemas and add corresponding u…

6c42ae8

…nit tests. This commit provides a basic fix for microsoft#6776, unblocking nullable reference types for ASP.Net Core.

fix: nullable enum support in OpenAPI schemas

89e9c09

X39 force-pushed the main branch from b5e86c9 to ea3c061 Compare November 29, 2025 15:22

fix: support integer-based enums for C#.

592710a

X39 force-pushed the main branch from ea3c061 to 592710a Compare November 29, 2025 15:25

X39 marked this pull request as ready for review November 29, 2025 15:29

lvde0 mentioned this pull request Jan 7, 2026

Incorrect C# property mapping with oneOf componet schema & null #6776

Open

gavinbarron requested changes Jan 23, 2026

View reviewed changes

X39 added 2 commits January 27, 2026 22:09

Add reverse test cases

8de37c7

Theese cover what is discussed in microsoft#7170 (comment)

Add GetSchemaReferenceIds test, covering nullable handling

d1eed2d

This test covers the requested changes, requested in https://github.com/microsoft/kiota/pull/7170/changes/BASE..592710aa6905adea20c73192cf204a3b6f83f2fa#r2722212419

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X39 commented Nov 28, 2025 •

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X39 commented Dec 11, 2025 •

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