fix(core) discriminatorType in oneOf interfaces

[jpfinne]

fix #24769, fix #19194

Improve resolution of DefaultCodegen.getDiscriminatorType by resolving the best common type in all mapped discriminators.

Matching $ref types are used. Otherwise the types enum, integer, string, object are used.

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---

Summary by cubic

Fixes #24769 and #19194 by inferring Java oneOf discriminator getter types from all mapped schemas instead of defaulting to Object. Constant string discriminators now generate Enum getters, while Kotlin keeps its existing string behavior.

• Resolves discriminator properties through $ref and allOf schemas.
• Preserves shared integer, number, and referenced enum types, with String or Object fallbacks when no common type exists; Java gains an enum mapping to Enum.
• Adds regression coverage for Java and Spring generators.

^{Written for commit 97909e8. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 7 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java:343">
P2: When the discriminator is inherited through `allOf`, this check misses the parent mapping because the child has no direct discriminator. Traverse referenced/allOf parents to locate the inherited discriminator before collecting mapped schemas.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: When the discriminator is inherited through allOf, this check misses the parent mapping because the child has no direct discriminator. Traverse referenced/allOf parents to locate the inherited discriminator before collecting mapped schemas.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java, line 343:

<comment>When the discriminator is inherited through `allOf`, this check misses the parent mapping because the child has no direct discriminator. Traverse referenced/allOf parents to locate the inherited discriminator before collecting mapped schemas.</comment>

<file context>
@@ -322,6 +323,60 @@ private static CodegenProperty getDiscriminatorCodegenProperty(OpenAPI openAPI,
+
+
+    public static List<Schema> getMappedSchemas(OpenAPI openAPI, Schema schema) {
+        if (schema.getDiscriminator() != null && schema.getDiscriminator().getMapping() != null) {
+            return schema.getDiscriminator().getMapping().values().stream()
+                    .map(ref -> ModelUtils.getSchema(openAPI, ModelUtils.getSimpleRef(ref)))
</file context>

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[Mattias-Sehlstedt]

The docstring here is not correct anymore it seems since it returns Schema rather than a simple type (which I assume was just String earlier)?

[Mattias-Sehlstedt]

Should this commented line be removed?

[Mattias-Sehlstedt]

Could you add #19194 as an issue being fixed as well by this?

Edit: it seem that one needs to have the full syntax to get proper linking for Multiple issues. So fix #24769, fix #19194.

[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 4 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 4 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 3 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

1 issue found across 2 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java:336">
P3: The new local variable `properties` is dead code: it is computed but never read anywhere in `getDistinctTypes`. It also forces a second full run of the recursive `findProperty` over every mapped schema (the same work the `return` statement repeats) and ends with a stray double semicolon. Drop the line entirely.</violation>
</file>

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

P3: The new local variable properties is dead code: it is computed but never read anywhere in getDistinctTypes. It also forces a second full run of the recursive findProperty over every mapped schema (the same work the return statement repeats) and ends with a stray double semicolon. Drop the line entirely.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/DiscriminatorUtils.java, line 336:

<comment>The new local variable `properties` is dead code: it is computed but never read anywhere in `getDistinctTypes`. It also forces a second full run of the recursive `findProperty` over every mapped schema (the same work the `return` statement repeats) and ends with a stray double semicolon. Drop the line entirely.</comment>

<file context>
@@ -332,6 +332,8 @@ private static CodegenProperty getDiscriminatorCodegenProperty(OpenAPI openAPI,
     public static List<Schema> getDistinctTypes(OpenAPI openAPI, Schema schema, String discPropName) {
         List<Schema> mappedSchemas = getMappedSchemas(openAPI, schema);
+
+        List<Schema> properties = mappedSchemas.stream().map(sc -> findProperty(openAPI, sc, discPropName, new HashSet<>())).collect(Collectors.toList());;
         return mappedSchemas.stream().map(sc -> findProperty(openAPI, sc, discPropName, new HashSet<>()))
                 .filter(Objects::nonNull)
</file context>