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Fix C# GenericHost oneOf serialization for referenced models #24674

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Fix C# GenericHost oneOf serialization for referenced models #24674

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f6aa83f
fix(csharp): serialize oneOf referenced models in generichost
madhus1218 Aug 11, 2026
e55db64
fix(csharp): handle generichost oneOf converter edge cases
madhus1218 Aug 11, 2026
71cbb72
Merge remote-tracking branch 'upstream/master' into fix-csharp-generi…
madhus1218 Sep 3, 2026
c548cf9
fix(csharp): address generichost oneOf review feedback
codex Sep 3, 2026
65de16d
fix(csharp): deserialize primitive oneOf values in GenericHost
madhus1218 Sep 3, 2026
f4118dc
fix(csharp): restore GenericHost JsonConverter template
madhus1218 Sep 3, 2026
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107 changes: 92 additions & 15 deletions .../openapi-generator/src/main/resources/csharp/libraries/generichost/JsonConverter.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,25 @@
{{#lambda.trimLineBreaks}}
int currentDepth = utf8JsonReader.CurrentDepth;

{{#composedSchemas.oneOf}}
{{#-first}}
bool oneOfHasPrimitiveType = false;
{{/-first}}
{{#isPrimitiveType}}
oneOfHasPrimitiveType = true;
{{/isPrimitiveType}}
{{#-last}}

if (!oneOfHasPrimitiveType &&
utf8JsonReader.TokenType != JsonTokenType.StartObject &&
utf8JsonReader.TokenType != JsonTokenType.StartArray)
throw new JsonException();
{{/-last}}
{{/composedSchemas.oneOf}}
{{^composedSchemas.oneOf}}
if (utf8JsonReader.TokenType != JsonTokenType.StartObject && utf8JsonReader.TokenType != JsonTokenType.StartArray)
throw new JsonException();
{{/composedSchemas.oneOf}}

JsonTokenType startingTokenType = utf8JsonReader.TokenType;

Expand Down Expand Up @@ -113,24 +130,40 @@
{{{datatypeWithEnum}}}{{nrt?}}{{^nrt}}{{#vendorExtensions.x-is-value-type}}?{{/vendorExtensions.x-is-value-type}}{{/nrt}} {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}} = default;
{{#-last}}

Utf8JsonReader utf8JsonReaderOneOf = utf8JsonReader;
while (utf8JsonReaderOneOf.Read())
{
if (startingTokenType == JsonTokenType.StartObject && utf8JsonReaderOneOf.TokenType == JsonTokenType.EndObject && currentDepth == utf8JsonReaderOneOf.CurrentDepth)
break;

if (startingTokenType == JsonTokenType.StartArray && utf8JsonReaderOneOf.TokenType == JsonTokenType.EndArray && currentDepth == utf8JsonReaderOneOf.CurrentDepth)
break;
if (oneOfHasPrimitiveType &&
startingTokenType != JsonTokenType.StartObject &&
startingTokenType != JsonTokenType.StartArray)
{
{{#oneOf}}
Utf8JsonReader utf8JsonReader{{name}} = utf8JsonReader;
ClientUtils.TryDeserialize<{{{datatypeWithEnum}}}{{nrt?}}{{^nrt}}{{#vendorExtensions.x-is-value-type}}?{{/vendorExtensions.x-is-value-type}}{{/nrt}}>(ref utf8JsonReader{{name}}, jsonSerializerOptions, out {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}});
{{^-last}}

if (utf8JsonReaderOneOf.TokenType == JsonTokenType.PropertyName && currentDepth == utf8JsonReaderOneOf.CurrentDepth - 1)
{{/-last}}
{{/oneOf}}
}
else
{
Utf8JsonReader utf8JsonReaderOneOf = utf8JsonReader;
while (utf8JsonReaderOneOf.Read())
{
{{#oneOf}}
Utf8JsonReader utf8JsonReader{{name}} = utf8JsonReader;
ClientUtils.TryDeserialize<{{{datatypeWithEnum}}}{{nrt?}}{{^nrt}}{{#vendorExtensions.x-is-value-type}}?{{/vendorExtensions.x-is-value-type}}{{/nrt}}>(ref utf8JsonReader{{name}}, jsonSerializerOptions, out {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}});
{{^-last}}
if (startingTokenType == JsonTokenType.StartObject && utf8JsonReaderOneOf.TokenType == JsonTokenType.EndObject && currentDepth == utf8JsonReaderOneOf.CurrentDepth)
break;

{{/-last}}
{{/oneOf}}
if (startingTokenType == JsonTokenType.StartArray && utf8JsonReaderOneOf.TokenType == JsonTokenType.EndArray && currentDepth == utf8JsonReaderOneOf.CurrentDepth)
break;

if (utf8JsonReaderOneOf.TokenType == JsonTokenType.PropertyName && currentDepth == utf8JsonReaderOneOf.CurrentDepth - 1)
{
{{#oneOf}}
Utf8JsonReader utf8JsonReader{{name}} = utf8JsonReader;
ClientUtils.TryDeserialize<{{{datatypeWithEnum}}}{{nrt?}}{{^nrt}}{{#vendorExtensions.x-is-value-type}}?{{/vendorExtensions.x-is-value-type}}{{/nrt}}>(ref utf8JsonReader{{name}}, jsonSerializerOptions, out {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}});
{{^-last}}

{{/-last}}
{{/oneOf}}
}
}
}
{{/-last}}
Expand Down Expand Up @@ -376,7 +409,51 @@

{{/children}}
{{/discriminator}}
{{^model.discriminator}}
{{#composedSchemas}}
{{#oneOf}}
{{#isPrimitiveType}}
{{#isContainer}}
if ({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}} != null)
{
JsonSerializer.Serialize(writer, {{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}, jsonSerializerOptions);
return;
}

{{/isContainer}}
{{^isContainer}}
{{^vendorExtensions.x-duplicated-data-type}}
if ({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}} != null)
{
JsonSerializer.Serialize(writer, {{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}, jsonSerializerOptions);
return;
}

{{/vendorExtensions.x-duplicated-data-type}}
{{/isContainer}}
{{/isPrimitiveType}}
{{/oneOf}}
{{/composedSchemas}}
{{/model.discriminator}}
writer.WriteStartObject();
{{^model.discriminator}}
{{#composedSchemas}}
{{#oneOf}}
{{^vendorExtensions.x-duplicated-data-type}}
{{#isModel}}
{{^isContainer}}
if ({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}} != null)
{
{{baseType}}JsonConverter {{#lambda.camelcase_sanitize_param}}{{baseType}}JsonConverter{{/lambda.camelcase_sanitize_param}} = ({{baseType}}JsonConverter) jsonSerializerOptions.Converters.First(c => c.CanConvert({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}.GetType()));
{{#lambda.camelcase_sanitize_param}}{{baseType}}JsonConverter{{/lambda.camelcase_sanitize_param}}.WriteProperties(writer, {{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}, jsonSerializerOptions);
}

{{/isContainer}}
{{/isModel}}
{{/vendorExtensions.x-duplicated-data-type}}
{{/oneOf}}
{{/composedSchemas}}
{{/model.discriminator}}

{{#model.discriminator}}
{{#model.hasDiscriminatorWithNonEmptyMapping}}
Expand Down Expand Up @@ -678,4 +755,4 @@
{{/lambda.trimLineBreaks}}
{{/lambda.trimTrailingWithNewLine}}
}
}
}
106 changes: 64 additions & 42 deletions modules/openapi-generator/src/test/resources/3_0/oneOf.yaml
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@@ -1,46 +1,68 @@
openapi: 3.0.1

info:
title: fruity
version: 0.0.1
title: fruity
version: 0.0.1

paths:
/:
get:
responses:
'200':
description: desc
content:
application/json:
schema:
$ref: '#/components/schemas/fruit'
/:
get:
responses:
'200':
description: desc
content:
application/json:
schema:
$ref: '#/components/schemas/fruit'

components:
schemas:
fruit:
title: fruit
properties:
color:
type: string
oneOf:
- $ref: '#/components/schemas/apple'
- $ref: '#/components/schemas/banana'
- $ref: '#/components/schemas/orange'
# additionalProperties:
# type: string
# uncomment this when https://github.com/swagger-api/swagger-parser/issues/1252 is resolved
apple:
title: apple
type: object
properties:
kind:
type: string
banana:
title: banana
type: object
properties:
count:
type: number
orange:
title: orange
type: object
properties:
sweet:
type: boolean
schemas:
fruit:
title: fruit
properties:
color:
type: string
oneOf:
- $ref: '#/components/schemas/apple'
- $ref: '#/components/schemas/banana'
- $ref: '#/components/schemas/orange'

inlineOneOfModel:

@cubic-dev-ai cubic-dev-ai Bot Sep 3, 2026

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P3: The two newly added schemas inlineOneOfModel and union are not referenced by any test. A repository-wide search shows the only consumers of this shared fixture (DefaultCodegenTest, RubyClientCodegenTest, JavaClientCodegenTest, ProtobufSchemaCodegenTest, Swift6ClientCodegenTest) all target only the pre-existing fruit schema, and no test or sample references inlineOneOfModel or union. They therefore add no regression coverage (the PR's referenced-model tests use fruit) and leave dead content in a shared test resource. Add a test that exercises these schemas, or drop them.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/test/resources/3_0/oneOf.yaml, line 30:

<comment>The two newly added schemas `inlineOneOfModel` and `union` are not referenced by any test. A repository-wide search shows the only consumers of this shared fixture (`DefaultCodegenTest`, `RubyClientCodegenTest`, `JavaClientCodegenTest`, `ProtobufSchemaCodegenTest`, `Swift6ClientCodegenTest`) all target only the pre-existing `fruit` schema, and no test or sample references `inlineOneOfModel` or `union`. They therefore add no regression coverage (the PR's referenced-model tests use `fruit`) and leave dead content in a shared test resource. Add a test that exercises these schemas, or drop them.</comment>

<file context>
@@ -1,46 +1,68 @@
+        - $ref: '#/components/schemas/banana'
+        - $ref: '#/components/schemas/orange'
+
+    inlineOneOfModel:
+      title: inlineOneOfModel
+      type: object
</file context>

title: inlineOneOfModel
type: object
properties:
value:
oneOf:
- type: string
- type: integer

union:
title: union
oneOf:
- type: string
- type: integer

apple:
title: apple
type: object
properties:
kind:
type: string

banana:
title: banana
type: object
properties:
count:
type: number

orange:
title: orange
type: object
properties:
sweet:
type: boolean

# additionalProperties:
# type: string
# uncomment this when https://github.com/swagger-api/swagger-parser/issues/1252 is resolved
12 changes: 12 additions & 0 deletions ...e/csharp/generichost/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/OneOfNullableTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -179,6 +179,18 @@ public override OneOfNullableTest Read(ref Utf8JsonReader utf8JsonReader, Type t
/// <exception cref="NotImplementedException"></exception>
public override void Write(Utf8JsonWriter writer, OneOfNullableTest oneOfNullableTest, JsonSerializerOptions jsonSerializerOptions)
{
if (oneOfNullableTest.Int != null)
{
JsonSerializer.Serialize(writer, oneOfNullableTest.Int, jsonSerializerOptions);
return;
}

if (oneOfNullableTest.String != null)
{
JsonSerializer.Serialize(writer, oneOfNullableTest.String, jsonSerializerOptions);
return;
}

writer.WriteStartObject();

WriteProperties(writer, oneOfNullableTest, jsonSerializerOptions);
Expand Down
12 changes: 12 additions & 0 deletions ...st/latest/AnnotatedEnum/src/Org.OpenAPITools/Model/ParentWithPluralOneOfPropertyNumber.cs
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Expand Up @@ -178,6 +178,18 @@ public override ParentWithPluralOneOfPropertyNumber Read(ref Utf8JsonReader utf8
/// <exception cref="NotImplementedException"></exception>
public override void Write(Utf8JsonWriter writer, ParentWithPluralOneOfPropertyNumber parentWithPluralOneOfPropertyNumber, JsonSerializerOptions jsonSerializerOptions)
{
if (parentWithPluralOneOfPropertyNumber.Number != null)
{
JsonSerializer.Serialize(writer, parentWithPluralOneOfPropertyNumber.Number, jsonSerializerOptions);
return;
}

if (parentWithPluralOneOfPropertyNumber.Number2 != null)
{
JsonSerializer.Serialize(writer, parentWithPluralOneOfPropertyNumber.Number2, jsonSerializerOptions);
return;
}

writer.WriteStartObject();

WriteProperties(writer, parentWithPluralOneOfPropertyNumber, jsonSerializerOptions);
Expand Down
27 changes: 27 additions & 0 deletions ...rp/generichost/latest/OneOfList/src/Org.OpenAPITools.Test/Model/OneOfArrayRequestTests.cs
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Expand Up @@ -14,6 +14,7 @@
using System.Linq;
using System.IO;
using System.Collections.Generic;
using System.Text.Json;
using Org.OpenAPITools.Model;
using Org.OpenAPITools.Client;
using System.Reflection;
Expand Down Expand Up @@ -52,5 +53,31 @@ public void OneOfArrayRequestInstanceTest()
// TODO uncomment below to test "IsType" OneOfArrayRequest
//Assert.IsType<OneOfArrayRequest>(instance);
}

[Fact]
public void SerializeOneOfStringArray()
{
var options = new JsonSerializerOptions();
options.Converters.Add(new OneOfArrayRequestJsonConverter());
var request = new OneOfArrayRequest(new List<string> { "first", "second" });

string json = JsonSerializer.Serialize(request, options);

Assert.Equal("[\"first\",\"second\"]", json);
}

[Fact]
public void SerializeOneOfModelArray()
{
var options = new JsonSerializerOptions();
options.Converters.Add(new OneOfArrayRequestJsonConverter());
options.Converters.Add(new TestObjectJsonConverter());
var item = new TestObject(new Option<string?>("example"));
var request = new OneOfArrayRequest(new List<TestObject> { item });

string json = JsonSerializer.Serialize(request, options);

Assert.Equal("[{\"name\":\"example\"}]", json);
}
}
}
12 changes: 12 additions & 0 deletions ...store/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Model/OneOfArrayRequest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,18 @@ public override OneOfArrayRequest Read(ref Utf8JsonReader utf8JsonReader, Type t
/// <exception cref="NotImplementedException"></exception>
public override void Write(Utf8JsonWriter writer, OneOfArrayRequest oneOfArrayRequest, JsonSerializerOptions jsonSerializerOptions)
{
if (oneOfArrayRequest.List != null)
{
JsonSerializer.Serialize(writer, oneOfArrayRequest.List, jsonSerializerOptions);
return;
}

if (oneOfArrayRequest.List1 != null)
{
JsonSerializer.Serialize(writer, oneOfArrayRequest.List1, jsonSerializerOptions);
return;
}

writer.WriteStartObject();

WriteProperties(writer, oneOfArrayRequest, jsonSerializerOptions);
Expand Down
11 changes: 11 additions & 0 deletions .../petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/Fruit.cs
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Expand Up @@ -205,6 +205,17 @@ public override Fruit Read(ref Utf8JsonReader utf8JsonReader, Type typeToConvert
public override void Write(Utf8JsonWriter writer, Fruit fruit, JsonSerializerOptions jsonSerializerOptions)
{
writer.WriteStartObject();
if (fruit.Apple != null)
{
AppleJsonConverter appleJsonConverter = (AppleJsonConverter) jsonSerializerOptions.Converters.First(c => c.CanConvert(fruit.Apple.GetType()));
appleJsonConverter.WriteProperties(writer, fruit.Apple, jsonSerializerOptions);
}

if (fruit.Banana != null)
{
BananaJsonConverter bananaJsonConverter = (BananaJsonConverter) jsonSerializerOptions.Converters.First(c => c.CanConvert(fruit.Banana.GetType()));
bananaJsonConverter.WriteProperties(writer, fruit.Banana, jsonSerializerOptions);
}

WriteProperties(writer, fruit, jsonSerializerOptions);
writer.WriteEndObject();
Expand Down
11 changes: 11 additions & 0 deletions ...tstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Model/FruitReq.cs
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Expand Up @@ -179,6 +179,17 @@ public override FruitReq Read(ref Utf8JsonReader utf8JsonReader, Type typeToConv
public override void Write(Utf8JsonWriter writer, FruitReq fruitReq, JsonSerializerOptions jsonSerializerOptions)
{
writer.WriteStartObject();
if (fruitReq.AppleReq != null)
{
AppleReqJsonConverter appleReqJsonConverter = (AppleReqJsonConverter) jsonSerializerOptions.Converters.First(c => c.CanConvert(fruitReq.AppleReq.GetType()));
appleReqJsonConverter.WriteProperties(writer, fruitReq.AppleReq, jsonSerializerOptions);
}

if (fruitReq.BananaReq != null)
{
BananaReqJsonConverter bananaReqJsonConverter = (BananaReqJsonConverter) jsonSerializerOptions.Converters.First(c => c.CanConvert(fruitReq.BananaReq.GetType()));
bananaReqJsonConverter.WriteProperties(writer, fruitReq.BananaReq, jsonSerializerOptions);
}

WriteProperties(writer, fruitReq, jsonSerializerOptions);
writer.WriteEndObject();
Expand Down
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