supabase-js .single() returning array

Bug report

Describe the bug

After updating to supabase-js v2 rc-1, appending .single() to a query continues to return an array in the actual data. The types from the new type gen properly infer that a single non-array item should be returned when .single() is used, so manually specifying data[0] produces an any type inference. However, logging data shows that it was returned as an array. The same code works as expected in the latest supabase-js v1.

To Reproduce

const { data, error } = await supabase
    .from('my_table')
    .select(
    `
    *,
    my_relation (
      *
    )
  `
    )
    .eq('id', itemId)
    .single();

// `data` is inferenced correctly as a single `my_table` item
// Additionally, error is null, so .single() did not throw, since there was 1 item returned
// however, data itself is logged as an array of length 1 of the item
// `[{ /* ...itemContents */ }]`
console.log(data);

Expected behavior

.single() should cause data to return the single object (or throw if multiple) not an array of the object (as inferred by the types).

System information

• OS: Windows
• Browser chrome
• Version of supabase-js: 2.0.0-rc.1
• Version of Node.js: 16.14.2

[Daynil]

Wow, can’t believe I haven’t run into this particular javascript idiosyncrasy until now! Thanks @soedirgo!!

I adjusted my code and everything works exactly as expected:

export async function supabaseFetch(
  input: RequestInfo | URL,
  init?: RequestInit
) {
    if (init.headers instanceof Headers) {
        init.headers.set('Authorization', `Bearer ${await getSupabaseToken()}`);
    } else {
        init.headers['Authorization'] = `Bearer ${await getSupabaseToken()}`;
    }
    return fetch(input, init);
}

[soedirgo]

Sorry for the late reply - had a look at the repro link (thanks again!) and it seems like this was caused by init.headers being a Headers object instead of a { [key: string]: string }. You can get the actual values if you do:

for (const [headerKey, headerValue] of init?.headers?.entries() ?? []) {
  console.log('header:', headerKey, headerValue)
}

That said, we don’t make any guarantee that this will always be Headers, so you’ll need to handle both cases.