make ZodString.date(), ZodString.time(), and ZodString.datetime() only accept valid date and time

[szamanr]

#1766 added .date() function but it uses a simple regex \d{4}-\d{2}-\d{2}, which allows many invalid dates. similar behaviour happens for .time() and .datetime().

if we must use regex for date validation, then i propose a change that:

• rejects invalid dates such as 2024-01-32 or 2024-13-01
• correctly handles 30th and 31st day based on the month
• is still fairly readable, as far as regexes go

one caveat is that it always accepts 29 feb, but i think that's acceptable. it's an improvement over the existing code, where non-valid dates are accepted.

you can check some test cases here: https://regexr.com/7ulgo

todo:

• add test cases
• also validate time
• add test cases for time

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[szamanr]

cc @igalklebanov @colinhacks since this hasn't been released yet, maybe we can do a quick patch before the release.

[colinhacks]

I think this is a good idea, but it does introduce some inconsistency with .datetime(), which still doesn't enforce this. We should the datetime logic to do the same. Thoughts @igalklebanov? I'd be okay releasing that in a minor version, arguably it's a bugfix.

Also, your PR seems to have only updated the code in deno/lib? Just update src and deno/lib should get regenerated when you push.

[igalklebanov]

Hey 👋

Good idea!

As @colinhacks said, all datelike stuff should be aligned.

This extra leap day occurs in each year that is a multiple of 4, except for years evenly divisible by 100 but not by 400
https://en.wikipedia.org/wiki/Leap_year

Could check year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0) for leap years when xxxx-02-29.

[szamanr]

.datetime() and .date() are using the same regex under the hood.

i added a regex for valid time, moved the code to src dir, and updated the PR title to reflect all changes.

[colinhacks]

Rebased onto the changes I made in #2522

[colinhacks]

Thanks @szamanr! 🙌

[Shumuu]

Why does it need to be a regex? Couldn't you check it easier with a Date instance or are there some problems in different runtimes?

[szamanr]

Why does it need to be a regex? Couldn't you check it easier with a Date instance or are there some problems in different runtimes?

@Shumuu how would you achieve that? i've seen some implementations using a function that checked if new Date(dateString).getTime() is a number, but that doesn't work properly. for example:

new Date("2000-02-31").getTime() // should be invalid
> 951955200000

new Date("2000-04-31").getTime() // should be invalid
> 957139200000

let's say we used that - in that case, we would still have to use a regex first, to rule out all sorts of strings that Date() constructor accepts, e.g. "123".

either way, i tend to not put trust in native Date, given that it has many issues. the best way to solve this would be to outsource the logic to a 3rd party library. e.g. date-fns has a function that would be perfect for this: isMatch(dateString, "yyyy-MM-dd"). but i noticed zod doesn't ship with any dependencies, so i assumed this is not accepted here.

[Shumuu]

The way I solve it is creating a Date like this

new Date("2023-02-29") and then I check on the date instance if the day, the month and the year are equal to what I passed in. Creating an invalid Date like this will result in 2023-03-01.

[colinhacks]

There's a lot of other stuff to validate besides "is this date valid". Users can specify whether to allow timezone offsets, unqualified dates, sub-second precision, etc. So we're going to be doing regex validation regardless. We could use regex to check those things then instantiate a new Date to check date validity. I'll do some benchmarking to know which is faster.

[colinhacks]

This has landed in Zod 3.23.

https://github.com/colinhacks/zod/releases/tag/v3.23.0