Query parameter that is a union of string and string array is incorrectly parsed

[harveylee]

What version of Elysia is running?

1.2.10

What platform is your computer?

Linux 5.15.153.1-microsoft-standard-WSL2 x86_64 unknown

What steps can reproduce the bug?

import { treaty } from '@elysiajs/eden'
import { describe, expect, it } from 'bun:test'
import { Elysia, t } from 'elysia'

describe('Failing: string array or string query', async () => {
    const server = new Elysia()
      .get('/query', async ({ query: { tags } }) => {
        console.log(tags) // outputs 'a'
        return { tags }
      }, {
        query: t.Partial(t.Object({
          tags: t.Union([t.Array(t.String()), t.String()]), // string[] | string
        })),
      })
    const api = treaty(server)

    it('query: string array', async () => {
      const res = await api.query.get({ query: { tags: ['a', 'b', 'c'] } })
      if (res.error) throw res.error
      expect(res.data.tags).toEqual(['a', 'b', 'c'])
    }) // instead, res.data.tags === 'a'
})

What is the expected behavior?

query.tags is parsed as ['a', 'b', 'c'] (i.e. an array)

What do you see instead?

query.tags is parsed as 'a' (i.e. just the first value)

Additional information

No response

Have you try removing the node_modules and bun.lockb and try again yet?

No

[hisamafahri]

My suspicion is that there's a different behavior if you call:

1. http://localhost:3000/?tags=a&tags=b&&tags=c, and
2. http://localhost:3000/?tags=a,b,c

I think the "problem" here that if you query it with the first approach, the query function params in the ({ query: { tags } }) => {} will only return the first value.

(note: looks like api.query.get({ query: { tags: ['a', 'b', 'c'] } }) do it in the first approach).

For now, you can either parse it manually (via the request.url) or use the 2nd pattern.

[harveylee]

More info:
The issue has to do with the tags: t.Union([t.Array(t.String()), t.String()]) in the query schema. The query parameter is correctly parsed as the full array if the query schema specifies tags: t.Array(t.String()) - but then you can't pass a single string (acceptable workaround in my use case, but perhaps an unnecessary limitation).

@hisamafahri I couldn't find any straightforward way to get Eden Treaty to format query array parameters as a comma-separated list - do you know if there's a way? I saw elysiajs/eden#127 which would help.

But in any case, doesn't seem like Elysia recognises a comma-separated list out of the box:

it('query: string array, non-exploded', async () => {
  server.listen(3099)
  const res = await fetch('http://localhost:3099/query?tags=a,b,c')
  const data = await res.json()
  expect(data.tags).toEqual(['a', 'b', 'c'])
})

...also fails (Elysia parses tags as a single string: 'a,b,c')

[hisamafahri]

to get Eden Treaty to format query array parameters as a comma-separated list

You can do this:

await api.query.get({ query: { tags: ['a', 'b', 'c'].join(",") } })

But in any case, doesn't seem like Elysia recognises a comma-separated list out of the box

Yes, that one is entering an area of debate whether a framework should handle that or not. It's a matter of preference.

But, either way, one of the "hacky" way is by manually parse the request url:

.get('/', async ({ request }) => {
    const url = new URL(request.url)
    const tags = url.searchParams.get('tags')?.split(',')
    return { tags }
  })