useMutation/useQuery data not undefined by default

[schulzf]

I'm building hooks with zod to make a library for an api i'll be using in multiple apps.

When I call the useMutation hook for login for example, typescript is assuming that data will always be present

const { data, mutate } = useLoginMutation()

I have

const data: {
    token: string;
    name: string;
    tokenPass: string;
}

Whereas it should be

const data: {
    token: string;
    name: string;
    tokenPass: string;
} | undefined

Here is my hook:

const LoginInput = z
  .object({ email: z.string(), password: z.string() })
  .transform((data) => ({ Email: data.email, Password: data.password }))
export type TLoginInput = z.input<typeof LoginInput>

const LoginOutput = z
  .object({ Token: z.string(), Name: z.string(), TokenPass: z.string() })
  .transform((data) => ({ token: data.Token, name: data.Name, tokenPass: data.TokenPass }))
export type TLoginOutput = z.output<typeof LoginOutput>

const mutate = fetcher<TLoginInput, TLoginOutput>({
  method: HTTPMethod.POST,
  path: `/accounts/login`,
  requestSchema: LoginInput,
  responseSchema: LoginOutput,
})

export const useLoginMutation = (options?: UseMutationOptions<TLoginOutput, unknown, TLoginInput>) => {
  return useMutation(['login'], (input: TLoginInput) => mutate(input), {
    retry: false,
    onSuccess: ({ token }) => {
      axiosClient.defaults.headers.common['Authorization'] = `Bearer ${token}`
    },
    ...options,
  })
}

Here is the fetcher

export const axiosClient = axios.create({ baseURL: `https://someurl.com/api` })

export default function fetcher<Request, Response>({
  method,
  path,
  requestSchema,
  responseSchema,
}: {
  method: HTTPMethod
  path: string
  requestSchema: z.ZodEffects<ZodTypeAny> | z.ZodType<Request>
  responseSchema: z.ZodEffects<ZodTypeAny> | z.ZodType<Response>
}): (data: Request) => Promise<Response> {
  return function (requestData: Request) {
    async function apiCall() {
      const parsedRequest = requestSchema.parse(requestData)
      const response = await axiosClient({
        method,
        url: path,
        [method === HTTPMethod.GET ? 'params' : 'data']: parsedRequest,
      })

      return responseSchema.parse(response.data)
    }

    return apiCall()
  }
}

[schulzf]

forgot to enable structNullChecks