Using .safeExtend() without repeating definitions

[lukes-marvin-com]

Hi all, thanks for reading.

I have a base schema for api validation -

const baseSchema = z.object({
  name: z.string().optional(),
  role: z.enum(['user', 'admin']),
  projectType: z.array(z.enum(['Big', 'Small'])).optional(),
})

I am trying to safe extend this so I can benefit from the base schema role enum and projectType array types without having to repeat this logic, I just want to add error messaging and make it required. I want this because the api doesn't require the role or project necessarily and I might want to use this base schema elsewhere in another form that doesn't require a role input at all. So I don't want to add much to the base schema. Also the error message might be different elsewhere, so I think that safe extending off of a more general base schema without explicit error messages is required for me.

So this works:

const formSchema = baseSchema.safeExtend({
  role: z.enum(['user', 'admin']).nonoptional('please provide a user type'),
  projectType: z.array(z.enum(['Big', 'Small'], "project type required")).min(1, 'project type...'),
})

But it would be super nice to do something like this (not have to use the same enum values) -

const formSchema = baseSchema.safeExtend({
  role: baseSchema.shape.nonoptional('please provi....'),
  projectType: leadsSchema.shape.projectType('Please provide...')
})

the project type is a form input of multiple checkboxes that get added to an array. The default value from react hook form comes in as false. I also realize I could provide a default value to react hook form but it would be nice to not have to.

[dosubot[bot]]

Hi @lukes-marvin-com! I'm Dosu and I’m helping the zod team.

You can absolutely reuse your base schema's field definitions when extending with .safeExtend()—no need to repeat enum values or array types. Just reference the base schema's .shape property and chain on your new requirements or error messages. For example:

const formSchema = baseSchema.safeExtend({
  role: baseSchema.shape.role.nonoptional('please provide a user type'),
  projectType: baseSchema.shape.projectType.min(1, 'project type...')
});

This pattern is supported and recommended for avoiding duplication and customizing error messages or required/optional status in extensions. You can also use spread syntax to build new schemas from shared shapes if you prefer that style. See the official docs and this discussion for more details.

For your React Hook Form integration: if the checkbox group returns false instead of an array, you'll want to preprocess or coerce the value before Zod validation, since Zod expects an array for projectType.

If this solves your question, feel free to close the issue! If you need more help, a minimal runnable reproduction is always welcome.

To reply, just mention @dosu.

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[lukes-marvin-com]

@dosu

That doesn't work though.

For role -

Since it only accepts either of the two enum values, there is no possible 'default' value to provide that won't trigger the enum error it seems like. using your provided code I still get an error that it's not one of the enum types. I don't want to provide a default type that is one of the enum types because I don't want to pre-select an option for the user. I also don't want to add an empty string as an option because the api won't accept an empty string, only undefined or one of the enums.

For project type -

It doesn't appear that min is a method available on aseSchema.shape.projectType