Bug report

[x] I confirm this is a bug with Supabase, not with my own application.
[x] I confirm I have searched the Docs, GitHub Discussions, and Discord.

Describe the bug

I have a profiles and a customers table, with a one-to-one relationship:

profiles: {
  id: text, primary key
  ...
}
customers: {
  id: references profiles.id, primary key
  stripe_customer_id: text, unique
  ...
}

When doing a join between these, TypeScript thinks the type of customers is this:

{
    stripe_customer_id: string;
}[]

But when I run the code, this is the actual type I get:

{
    stripe_customer_id: string;
}

So when accessing the stripe_customer_id property, I get this type error:

Property 'stripe_customer_id' does not exist on type '{ stripe_customer_id: string; }[]'.

To Reproduce

const profile_result = await supabase
	.from('profiles')
	.select('id, customers ( stripe_customer_id )')
	.eq('id', params.id)
	.single()
if (profile_result.data) {
	console.log(profile_result.data.customers.stripe_customer_id)
    //                                        ^
    // Property 'stripe_customer_id' does not exist on
    // type '{ stripe_customer_id: string; }[]'.ts(2339)
}

Expected behavior

The TypeScript type should not be an array for one-to-one relationships. It should match the actual type

System information

OS: macOS
Version of supabase-js: 2.31.0
Version of Node.js: 18.14.2

Additional context

https://github.com/supabase/supabase-js/issues/723

Aug 04 '23 23:08 probablykasper

I'm using this as a workaround for now:

export function cast<T>(notAnArray: T[]): T {
  return notAnArray as T;
}

And then:

console.log(cast(profile_result.data.customers).stripe_customer_id)

Aug 07 '23 11:08 aslakhellesoy

Update: I've changed my workaround to this:

export function fixOneToOne<T>(objectOrNull: T[]): T | null {
  return (objectOrNull as T) || null;
}

I've changed the return type to T | null because the relationship may indeed be null. In the example above, this would happen when there is no customers record for the given profile.

In the example above, the correct type should be:

{
    stripe_customer_id: string;
} | null

Aug 25 '23 11:08 aslakhellesoy

I encountered the same issue today and I found another workaround.

const profile_result = await supabase
	.from('profiles')
	.select('id, customers ( stripe_customer_id )')
	.eq('id', params.id)
	.single()
        .returns<YourType[]>();

# type definition
type YourType {
    the type that you expect without the array
}