Create exact error message for z.array().length().

[john-schmitz]

Given this schema:

const testSchema = z.array(z.number()).length(4);

For arrays with less than 4 elements, it returns the message:

Should have at least 4 items

For arrays with more than 4 elements, it returns the message:

Should have at most 4 items

I wish instead for it to return a message explaining that it should be precisely 4 items:

Should have exactly 4 items

I know I could achieve that with a custom refine validation, but it would be nice to have it baked in.

Of course, if you find this suggestion valid, I could make a PR for it.

[maxArturo]

Hi @john-schmitz ! I'll provide my opinion based on what I see implemented. Here's the def for z.array().length()

  length(len: number, message?: errorUtil.ErrMessage): this {
    return this.min(len, message).max(len, message) as any;
  }

That's why you see the behavior described in your issue - min gets validated before max, and their respective messages get shown in the validation result. I believe building an exactly out of min and max is probably the way to do it (keeping in with the don't-repeat-yourself ethos).

However, there's an opportunity to build a more contextually-correct error message precisely in that line that gives a more contextually-correct error message, if you'd like to submit a PR.

[maxArturo]

Oh a final note - you don't need a custom refine validation! It's as easy as this

  const testSchema = z
    .array(z.number())
    .length(4, { message: "needs to be exactly 4" });

  testSchema.parse([]);

In case that saves you any trouble.

[john-schmitz]

fixed with pr #1620