fix: implement discriminations correctly in zod

[Georgegriff]

Status

READY

Description

Fixes #1906

This PR makes use of Discriminated unions in zod instead of chaning .or the main advantage of this is that zod can provide more accurate error messages as it will use the discriminator property to decide which zod schema to pick for the the rest of the validation of fields.

Before

export const testResponseItem = zod.object({
 "breed": zod.enum(['Labradoodle']),
 "cuteness": zod.number()
}).or(zod.object({
 "breed:" zod.enum(['Dachshund']),
 "length": zod.number()
}))
export const testResponse = zod.array(testResponseItem)

After

export const testResponseItem = zod.discriminatedUnion('breed', [zod.object({
 "breed": zod.enum(['Labradoodle']),
  "cuteness": zod.number()
}),zod.object({
 "breed:" zod.enum(['Dachshund']),
  "length": zod.number()
})])
export const testResponse = zod.array(testResponseItem)

By using '.or' you can end up with confusing messages like "invalid breed Dachshund" when switching a form between the types e.g. imagine having a radio button field with current value of Dachshund with validation errors .e.g. length not a number, and then you switch the "radio" to "Labradoodle" which changes the form field, the validation can get confused because it doesn't know which schema it should validate against because a .or cannot discriminate

Todos

• Tests
• Documentation
• Changelog Entry (unreleased)

[Georgegriff]

open to better ways of doing this... but with the separator only being a string I was struggling to come up with a way of saving this "metadata"

[melloware]

I personally don't have a more clever way but maybe @soartec-lab does?

[soartec-lab]

I have no discomfort with this either 👍

[Georgegriff]

its unfortunate that i can't do a full integration style test with this because there is some pre-processing of the schema in the core code which handles the expanding of the breed properties onto the types specifies in the discriminator

[Georgegriff]

Noticed in CI logs this spec was invalid and the name made me take a look, thought i'd fix it

[Georgegriff]

@melloware My first pass is ready to be reviewed whenever time allows

[soartec-lab]

Hi @Georgegriff
We updated the sample application with #1885 and noticed an error. cloud you fix this?

Error:  samples/hono/hono-with-zod/src/petstore.zod.ts: SyntaxError: Expression expected. (17:4)
Error:    15 |   "cuteness": zod.number(),
Error:    16 |   "breed": zod.enum(['Labradoodle'])
Error:  > 17 | }),.strict(),zod.object({
Error:       |    ^
Error:    18 |   "length": zod.number(),
Error:    19 |   "breed": zod.enum(['Dachshund'])
Error:    20 | }),.strict()]).or(zod.object({

[Georgegriff]

Yep i'll have a look now

[Georgegriff]

the .strict(): I see why this caused the bug, i would have thought .strict() should have been chained onto the object but its been separated for some reason, bizarre.

I think i can fix this though, i probably shouldn't be doing flatMap here

and need to merge properly.

[Georgegriff]

@soartec-lab PR for fix is here: #1923

[soartec-lab]

@Georgegriff
Thanks for your quickly fix it.