[Fix] [Regression] Resolve the discriminator type from a 3.1 sibling #22634

Mattias-Sehlstedt · 2026-01-08T11:49:29Z

With 7.18 I have started to encounter an error when I generate a oneOf-interface. The issue is that the interface's getter type has been changed from EnumValue to String, while all implementors still have the correct EnumValue that they are meant to implement.

I have tracked down the issue to the fact that I am using a 3.1 specification, where my disciminator also defines a unique description for the enum. This, combined with the introduction of #22364, has made it so that the definition

Fruit:
  type: object
  properties:
    fruitType:
      $ref: "#/components/schemas/FruitType"
      description: "test"

is normalized to

Fruit:
  type: object
  properties:
    fruitType:
      allOf: 
        $ref: "#/components/schemas/FruitType"
      description: "test"

which makes it so that the discriminator calculator loses the type FruitType, and instead falls back to String.

I have adjusted for this by adding so that the discriminator calculator considers this sibling structure as a possible scenario, and that it will go one $ref deeper if it sees that the initially encountered discriminator property is an allOf without any property.

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Summary by cubic

Fix discriminator type resolution for OpenAPI 3.1 when the discriminator property is wrapped in an allOf sibling, so oneOf interface getters return the enum type (e.g., FruitType) instead of String. Restores correct typing in generated Java webclient sealed interfaces.

Bug Fixes
- Drill into $ref when the discriminator property is an allOf without properties, preserving the enum type.
- Prevents the regression where oneOf interface getter types fell back to String after normalization.
New Features
- Added a 3.1 sealed interface sample and CI workflow path to validate behavior.
- Added unit tests for DefaultCodegen and Java client generation to ensure enum discriminator types are retained.

^{Written for commit a7dd54f. Summary will update on new commits.}

cubic-dev-ai

9 issues found across 117 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.

Prompt for AI agents (all issues)


Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java">

<violation number="1" location="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java:33">
P1: The `@JsonIgnoreProperties` annotation has an empty `value` where the discriminator property name should be. This will cause Jackson serialization issues. Compare to `BarRefOrValue.java` and `Fruit.java` where the discriminator property (e.g., `"@type"`, `"fruitType"`) is correctly populated.</violation>

<violation number="2" location="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java:36">
P1: The `@JsonTypeInfo` annotation has an empty `property` value. This will prevent Jackson from correctly deserializing the polymorphic type since it won't know which JSON property identifies the subtype. Compare to other generated interfaces like `Fruit.java` which correctly has `property = "fruitType"`.</violation>
</file>

<file name=".github/workflows/samples-java-client-jdk17.yaml">

<violation number="1" location=".github/workflows/samples-java-client-jdk17.yaml:10">
P1: Path mismatch: the actual directory is `webclient-sealedInterface_3_1` (underscores) but workflow references `webclient-sealedInterface-3.1` (hyphen with dot). This will prevent the workflow from triggering and cause build failures.</violation>

<violation number="2" location=".github/workflows/samples-java-client-jdk17.yaml:39">
P1: Path mismatch: should be `webclient-sealedInterface_3_1` to match the actual directory name. The build will fail with this incorrect path.</violation>
</file>

<file name="modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java">

<violation number="1" location="modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java:4073">
P2: Use `fileContains` instead of `fileContainsPattern` for literal string matching. The parentheses in `"public FruitType getFruitType()"` are regex special characters (grouping operators). While this works by accident (empty capture groups match nothing), it's fragile and semantically incorrect. The `fileContains` method exists for literal string matching.</violation>
</file>

<file name="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ServerConfiguration.java">

<violation number="1" location="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ServerConfiguration.java:55">
P2: Potential `NullPointerException` if `serverVariable.enumValues` is null. The `ServerVariable.enumValues` field defaults to null.</violation>
</file>

<file name="samples/client/others/java/webclient-sealedInterface_3_1/build.gradle">

<violation number="1" location="samples/client/others/java/webclient-sealedInterface_3_1/build.gradle:138">
P2: JUnit 5 test configuration is incomplete. Missing `junit-jupiter-engine` dependency which is required at runtime to execute tests. Without it, tests will compile but not run.</violation>
</file>

<file name="samples/client/others/java/webclient-sealedInterface_3_1/README.md">

<violation number="1" location="samples/client/others/java/webclient-sealedInterface_3_1/README.md:19">
P2: Incorrect Java version requirement. The README states 'Java 1.8+' but this sample uses sealed interfaces which require Java 17+. The pom.xml correctly specifies Java 17. Consider updating the README template to reflect the actual Java version requirement for sealed interface samples.</violation>
</file>

<file name="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/RFC3339JavaTimeModule.java">

<violation number="1" location="samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/RFC3339JavaTimeModule.java:32">
P1: Deserializers added after `super.setupModule(context)` will not be registered. In Jackson's `SimpleModule`, `setupModule` processes the deserializer collection when called. Move the `addDeserializer` calls to the constructor, or call them before `super.setupModule(context)`.</violation>
</file>

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cubic-dev-ai · 2026-01-08T11:54:22Z

...s/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java

+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.19.0-SNAPSHOT")
+@JsonIgnoreProperties(
+  value = "", // ignore manually set , it will be automatically generated by Jackson during serialization


P1: The @JsonIgnoreProperties annotation has an empty value where the discriminator property name should be. This will cause Jackson serialization issues. Compare to BarRefOrValue.java and Fruit.java where the discriminator property (e.g., "@type", "fruitType") is correctly populated.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java, line 33: <comment>The `@JsonIgnoreProperties` annotation has an empty `value` where the discriminator property name should be. This will cause Jackson serialization issues. Compare to `BarRefOrValue.java` and `Fruit.java` where the discriminator property (e.g., `"@type"`, `"fruitType"`) is correctly populated.</comment> <file context> @@ -0,0 +1,40 @@ + [email protected](value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.19.0-SNAPSHOT") +@JsonIgnoreProperties( + value = "", // ignore manually set , it will be automatically generated by Jackson during serialization + allowSetters = true // allows the to be set during deserialization +) </file context>

cubic-dev-ai · 2026-01-08T11:54:22Z

...s/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java

+  value = "", // ignore manually set , it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the  to be set during deserialization
+)
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "", visible = true)


P1: The @JsonTypeInfo annotation has an empty property value. This will prevent Jackson from correctly deserializing the polymorphic type since it won't know which JSON property identifies the subtype. Compare to other generated interfaces like Fruit.java which correctly has property = "fruitType".

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/model/Animal.java, line 36: <comment>The `@JsonTypeInfo` annotation has an empty `property` value. This will prevent Jackson from correctly deserializing the polymorphic type since it won't know which JSON property identifies the subtype. Compare to other generated interfaces like `Fruit.java` which correctly has `property = "fruitType"`.</comment> <file context> @@ -0,0 +1,40 @@ + value = "", // ignore manually set , it will be automatically generated by Jackson during serialization + allowSetters = true // allows the to be set during deserialization +) +@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "", visible = true) + +public sealed interface Animal permits Dog, Cat { </file context>

.github/workflows/samples-java-client-jdk17.yaml

cubic-dev-ai · 2026-01-08T11:54:23Z

...bclient-sealedInterface_3_1/src/main/java/org/openapitools/client/RFC3339JavaTimeModule.java

+       super.setupModule(context);
+
+       addDeserializer(Instant.class, RFC3339InstantDeserializer.INSTANT);
+       addDeserializer(OffsetDateTime.class, RFC3339InstantDeserializer.OFFSET_DATE_TIME);
+       addDeserializer(ZonedDateTime.class, RFC3339InstantDeserializer.ZONED_DATE_TIME);


P1: Deserializers added after super.setupModule(context) will not be registered. In Jackson's SimpleModule, setupModule processes the deserializer collection when called. Move the addDeserializer calls to the constructor, or call them before super.setupModule(context).

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/RFC3339JavaTimeModule.java, line 32: <comment>Deserializers added after `super.setupModule(context)` will not be registered. In Jackson's `SimpleModule`, `setupModule` processes the deserializer collection when called. Move the `addDeserializer` calls to the constructor, or call them before `super.setupModule(context)`.</comment> <file context> @@ -0,0 +1,39 @@ + + @Override + public void setupModule(SetupContext context) { + super.setupModule(context); + + addDeserializer(Instant.class, RFC3339InstantDeserializer.INSTANT); </file context>

Suggested change

super.setupModule(context);

addDeserializer(Instant.class, RFC3339InstantDeserializer.INSTANT);

addDeserializer(OffsetDateTime.class, RFC3339InstantDeserializer.OFFSET_DATE_TIME);

addDeserializer(ZonedDateTime.class, RFC3339InstantDeserializer.ZONED_DATE_TIME);

addDeserializer(Instant.class, RFC3339InstantDeserializer.INSTANT);

addDeserializer(OffsetDateTime.class, RFC3339InstantDeserializer.OFFSET_DATE_TIME);

addDeserializer(ZonedDateTime.class, RFC3339InstantDeserializer.ZONED_DATE_TIME);

super.setupModule(context);

...les/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java

cubic-dev-ai · 2026-01-08T11:54:23Z

...webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ServerConfiguration.java

+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {


P2: Potential NullPointerException if serverVariable.enumValues is null. The ServerVariable.enumValues field defaults to null.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ServerConfiguration.java, line 55: <comment>Potential `NullPointerException` if `serverVariable.enumValues` is null. The `ServerVariable.enumValues` field defaults to null.</comment> <file context> @@ -0,0 +1,72 @@ + + if (variables != null && variables.containsKey(name)) { + value = variables.get(name); + if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) { + throw new IllegalArgumentException("The variable " + name + " in the server URL has invalid value " + value + "."); + } </file context>

Suggested change

if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {

if (serverVariable.enumValues != null && !serverVariable.enumValues.isEmpty() && !serverVariable.enumValues.contains(value)) {

cubic-dev-ai · 2026-01-08T11:54:23Z

samples/client/others/java/webclient-sealedInterface_3_1/build.gradle

+    implementation "org.openapitools:jackson-databind-nullable:$jackson_databind_nullable_version"
+    implementation "com.fasterxml.jackson.datatype:jackson-datatype-jsr310:$jackson_version"
+    implementation "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version"
+    testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"


P2: JUnit 5 test configuration is incomplete. Missing junit-jupiter-engine dependency which is required at runtime to execute tests. Without it, tests will compile but not run.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/build.gradle, line 138: <comment>JUnit 5 test configuration is incomplete. Missing `junit-jupiter-engine` dependency which is required at runtime to execute tests. Without it, tests will compile but not run.</comment> <file context> @@ -0,0 +1,139 @@ + implementation "org.openapitools:jackson-databind-nullable:$jackson_databind_nullable_version" + implementation "com.fasterxml.jackson.datatype:jackson-datatype-jsr310:$jackson_version" + implementation "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version" + testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version" +} </file context>

Suggested change

testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"

testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"

testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junit_version"

cubic-dev-ai · 2026-01-08T11:54:23Z

samples/client/others/java/webclient-sealedInterface_3_1/README.md

+
+Building the API client library requires:
+
+1. Java 1.8+


P2: Incorrect Java version requirement. The README states 'Java 1.8+' but this sample uses sealed interfaces which require Java 17+. The pom.xml correctly specifies Java 17. Consider updating the README template to reflect the actual Java version requirement for sealed interface samples.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/others/java/webclient-sealedInterface_3_1/README.md, line 19: <comment>Incorrect Java version requirement. The README states 'Java 1.8+' but this sample uses sealed interfaces which require Java 17+. The pom.xml correctly specifies Java 17. Consider updating the README template to reflect the actual Java version requirement for sealed interface samples.</comment> <file context> @@ -0,0 +1,162 @@ + +Building the API client library requires: + +1. Java 1.8+ +2. Maven/Gradle + </file context>

Suggested change

1. Java 1.8+

1. Java 17+

Mattias-Sehlstedt · 2026-01-08T12:06:18Z

~~Pipeline issue due to gradlew not being runnable. I will investigate~~
I should have adjusted correctly for this now

Mattias-Sehlstedt force-pushed the oneOf-interface-regression branch from 19c7b1d to 977c551 Compare January 8, 2026 11:54

cubic-dev-ai bot reviewed Jan 8, 2026

View reviewed changes

Add support for resolving the discriminator type from a 3.1 sibling

b7d5e42

Mattias-Sehlstedt force-pushed the oneOf-interface-regression branch from 977c551 to b7d5e42 Compare January 8, 2026 12:00

Mattias-Sehlstedt added 2 commits January 8, 2026 17:59

Set gradlew to be executable

3a75e29

Generate sample FILES again

a7dd54f

Mattias-Sehlstedt changed the title ~~Add support for resolving the discriminator type from a 3.1 sibling~~ [Fix] [Regression] Resolve the discriminator type from a 3.1 sibling Jan 9, 2026

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[Fix] [Regression] Resolve the discriminator type from a 3.1 sibling #22634

[Fix] [Regression] Resolve the discriminator type from a 3.1 sibling #22634

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	if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
	if (serverVariable.enumValues != null && !serverVariable.enumValues.isEmpty() && !serverVariable.enumValues.contains(value)) {

	testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"
	testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"
	testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junit_version"

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[Fix] [Regression] Resolve the discriminator type from a 3.1 sibling #22634

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[Fix] [Regression] Resolve the discriminator type from a 3.1 sibling #22634

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