Optional serialization for deep object for query parameter as a plain, instead with bracket notation

[ulysses-ck]

Description

I have a Spring Backend app, that needs a Pageable object at the time of making a GET request. With Swagger UI, there's no problem to manage this, I can make it and works.

{
  "page": 0,
  "size": 1,
  "sort": [
    "string"
  ]
}

The problem starts when I make the codegen, I'm using the plugin @hey-api/client-fetch. It indeed uses the bracket notation and produces this:

http://localhost:8080/example?pageable[page]=0&pageable[size]=10

And my backend want this:

http://localhost:8080/example?page=0&size=10

For now, I used a custom fetch to accomplish it, that convert from bracket notation to plain query parameter.

const customFetch: typeof fetch = (input, init) => {
  let url: string;
  let requestInit: RequestInit;

  
  if (input instanceof Request) {
    url = input.url;
    requestInit = init ?? {
      method: input.method,
      headers: input.headers,
      body: input.body,
    };
  } else {
    url = input.toString();
    requestInit = init ?? {};
  }
  
  console.log("Before: ", url);

  url = url
    .replace(/pageable\[page\]=/g, "page=")
    .replace(/pageable\[size\]=/g, "size=")
    .replace(/pageable\[sort\]=/g, "sort=");

  console.log("After:", url);

  return fetch(url, requestInit);
};

I despite if it isn't a bug, because I setup the parser to take pageable as a keyword.

export default defineConfig({
  input: 'http://localhost:8080/v3/api-docs',
  output: 'src/client',
  plugins: [{
    name: '@hey-api/client-fetch',
    baseUrl: false,
    runtimeConfigPath: './src/backend-client.ts',
  }],
  parser: {
    transforms: {
      enums: 'root',
    },
    pagination: {
      keywords: [
        ...defaultPaginationKeywords,
        "pageable"
      ]
    }
  }
});

But could be useful to have this to make a plain object instead to treat bracket notation at backend, at least for Spring to work out of the box, besides be from backend or frontend side

[dosubot]

Hi @ulysses-ck! I'm Dosu and I’m helping the openapi-ts team.

Currently, @hey-api/client-fetch and openapi-ts do not support plain serialization for deep object query parameters out of the box—there’s no documented config or plugin to switch from bracket notation to plain parameters for cases like Spring Pageable objects. The recommended approach is to use a custom fetch function or a request interceptor to rewrite the query string before sending the request, which you’re already doing. The parser’s pagination.keywords option only affects parameter detection, not serialization format. If native support for plain serialization becomes a priority, monitoring project updates or contributing a feature request may be helpful, but as of now, your workaround is the standard solution.
Reference

To reply, just mention @dosu.

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