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[BUG] ExampleGenerator returns the string "{}" (or null) for `type: object` schemas without `properties`

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
java, openapi
Domain
api

Research direction

Find resolvePropertyToExample and resolveModelToExample in the Java code that implements ExampleGenerator; the issue does not name their file or a test. Start by reproducing with the provided OpenAPI schema and checking how unresolved $ref values are handled. Done means object schemas without properties produce an empty JSON object in both nested and top-level examples, rather than a string or null.

Written by the indexing model from the issue text.

Description

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?
Description

resolvePropertyToExample returns the Java string literal "{}" for an object schema without properties and for a $ref that cannot be resolved. Json.pretty then serializes it as a JSON string ("metadata" : "{}") instead of an empty object ("metadata" : { }), so the example has the wrong type (JSON Schema Validation wright-00, 5.21).

The same happens one level up. For a top-level model type: object without properties, resolveModelToExample falls through to return null, and generate(null, ["application/json"], "Anything") returns the example null. Through the CLI this model gets unaliased first, so the operation simply has no example; only programmatic callers see null.

openapi-generator version

7.25.0 (also current master).

OpenAPI declaration file content or url
components:
  schemas:
    Reading:
      type: object
      properties:
        metadata:
          type: object
Steps to reproduce

generate -g html → "Example data" shows "metadata" : "{}". Expected: "metadata" : { }.

Suggest a fix

Return new LinkedHashMap<>() (an empty map) instead of the string "{}" in both branches of resolvePropertyToExample, and also for object schemas without properties in resolveModelToExample.

Dominant language
Java
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Forks
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Avg merge
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Merged PRs (30d)
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