Add .toLowerCase() and .toUpperCase() to ZodString

[levinuncu]

This adds lowerCase() to ZodString.

z.string().lowerCase().parse('LOWERCASE') = 'lowercase'

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[JacobWeisenburger]

This already works:

console.log( z.string().parse( 'LOWERCASE' ).toLowerCase() ) // 'lowercase'

So why do we need another way of doing this?

[levinuncu]

Than why is there this:

console.log(z.string().trim().parse(' trim ')) // 'trim'

If you could just do this:

console.log(z.string().parse(' trim ').trim()) // 'trim'

[JacobWeisenburger]

Personally, I don't know why we need the trim method, because like you said, we can just do this:

console.log(z.string().parse(' trim ').trim()) // 'trim'

But ultimately, it's not my call weather or not things like this make it in. I'm just trying to ask for your reasoning about why we need lowerCase. To me, adding lowerCase simply because we have trim is not a good enough reason. Because then where do we stop adding things like this? Seems like a lot of scope creep.

[levinuncu]

Obviously you are right but trim() and lowerCase() could be used in scenarios where you have to parse the same zod schema several times.
So you dont have to call toLowerCase() everytime.

I know it's not ideal but imagine something like this:

const UserSchema = z.object({
	name: z.string().trim().lowerCase(),
	email: z.string().trim().lowerCase().email(),
)}

const User = UserSchema.parse(userData)

// or

const User = {
	name: userData.name.trim().toLowerCase(),
	email: userData.email.trim().toLowerCase(),
}

With zod you could reuse the Schema and don't have to pay attention to things like trim() or toLowerCase().

[colinhacks]

So why do we need another way of doing this?

There's value in only needing to declare this transform once, instead of per-parse.

I reluctantly added .trim() because I was resistant to modifying the input inside the parsing logic for ZodString. But ultimately it's a really clean API that's useful, so I decided to be less dogmatic about siloing all transformation logic in ZodEffect. We now have .endsWith and .startsWith too so it makes sense to add .toLowerCase() and .toUpperCase() too imo.