[BUG][java] Discriminator default for direct property enum $ref generates String.<value>

Author: mrickenCreated Sep 4, 2026Updated Sep 8, 2026

LabelsIssue: Bug

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator?
Have you tested with the latest master to confirm the issue still exists?
Have you searched for related issues/PRs?
What's the actual output vs expected output?
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Describe the bug

The Java client generator produces Java that does not compile when a discriminator property is a direct $ref to an inline enum property. The generated child constructor assigns the discriminator mapping value as though the property were String:

java

this.category = String.ARCHIVE;

String.ARCHIVE does not exist.

Minimal OpenAPI 3.1 input

yaml

openapi: 3.1.0
info:
  title: Shared category discriminator
  version: 1.0.0
paths: {}
components:
  schemas:
    CategorySource:
      type: object
      required:
        - category
      properties:
        category:
          type: string
          enum:
            - ARCHIVE
    CategoryEvent:
      type: object
      required:
        - category
      properties:
        category:
          description: Event category
          $ref: "#/components/schemas/CategorySource/properties/category"
      discriminator:
        propertyName: category
        mapping:
          ARCHIVE: "#/components/schemas/ArchiveCategoryEvent"
    ArchiveCategoryEvent:
      allOf:
        - $ref: "#/components/schemas/CategoryEvent"
        - type: object
          properties:
            value:
              type: string

Reproduction

bash

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar \
  generate \
  -g java \
  -i enum-discriminator.yaml \
  -o generated \
  --skip-validate-spec \
  --additional-properties modelNamePrefix=Stock,hideGenerationTimestamp=true

cd generated
mvn -q -DskipTests compile

Actual result

Latest master (b391b2b98c5926ee9842ef3bc863b57c4d824bbe, 7.26.0-SNAPSHOT) generates:

java

public StockArchiveCategoryEvent() {
    this.category = String.ARCHIVE;
}

Compilation fails:

error: cannot find symbol
  symbol:   variable ARCHIVE
  location: class String

The same failure occurs with OpenAPI Generator 7.24.0.

Expected result

The direct property reference should retain the enum type at the discriminator use site. The generated constructor should assign the enum member, rather than String.ARCHIVE, and the generated client should compile.

Source: OpenAPITools/openapi-generator

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