[BUG][TYPESCRIPT-AXIOS] Fields with `uniqueItems: true` generate `Set<T>`, but `Set` is serialized incorrectly (empty object)

[MaestroNek]

Description

When using the typescript-axios generator, properties with uniqueItems: true in the OpenAPI spec are generated as Set<T> in the TypeScript models.

However, Set values are not serialized correctly when sent to the server. In serializeDataIfNeeded, the Set is passed to JSON.stringify, which results in {} — an empty object — instead of a JSON array.

This leads to incorrect request payloads and breaks API communication.

openapi-generator version

Tested with version 7.14.0

OpenAPI declaration file content or url

  components:
    schemas:
      ExampleModel:
        type: object
        properties:
          tags:
            type: array
            items:
              type: string
            uniqueItems: true

Generation Details

openapi-generator-cli generate -i ./openapi.yaml -g typescript-axios -o ./generated

Generated model:

tags?: Set<string>;

Steps to reproduce

1. Use the OpenAPI schema above

2. Generate the typescript-axios client

3. Call any endpoint with tags: new Set(['a', 'b'])

4. Observe the actual payload sent over the network

Expected result:

{ "tags": ["a", "b"] }

Actual result:

{ "tags": {} }

Related issues/PRs

Couldn't find related open issues specific to this problem.

Suggest a fix

1. Serialize Set as Array inside serializeDataIfNeeded or related functions
2. Or generate Array instead of Set by default for uniqueItems: true, or at least provide a config flag to do so

[keepConcentration]

@MaestroNek @wing328

Do you mind if I take this issue and open a PR?

[MaestroNek]

@keepConcentration

I’d be glad if you do