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[Feature Request] support subtyping of primitives

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
20/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Quiet
Tech stack
typescript
Domain
backend

Research direction

Design-level request: decide how primitive subtypes are declared and how validation attributes reach array elements, then carry that through ZModel parsing, validation and generated TypeScript types. Begin with how type declarations and @length-style attributes are parsed today and how scalar arrays are typed, and resolve the open question about nullable elements (PostTag?[]). Done means type PostTag { value String @length(1, 5) } used as PostTag[] validates each element, with tests covering arrays and nullability.

Written by the indexing model from the issue text.

Description

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Currently, it is not possible to validate elements of scalar arrays:

model Post {
  tags String[] @length(1, 5) // what if I wanted a tag itself to be between 1 and 5 characters?
}

Describe the solution you'd like
A clear and concise description of what you want to happen.

Allow subtyping of primitives so that validation attributes can be applied to them, then referenced as the element type of an array.

type PostTag {
  value String @length(1, 5)
}

model Post {
  value PostTag[]
}

The above method wouldn't require changes to the schema language grammar. However, I will still note that the following syntax could be more intuitive to some because it doesn't use the implicit value property like the above, and is more like a type alias.

type PostTag = String @length(1, 5)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Validate in application code. But then there is some validation occurring as part of the schema definition and some happening elsewhere. It would be nice to centralize it.

Additional context
Add any other context or screenshots about the feature request here.

Open questions:

  1. Nullable array elements

    These (String?[]) are not currently allowed. Would these subtypes be forced as non-nullable, and required to be marked as nullable at the usage site (PostTag?)?

Dominant language
TypeScript
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Forks
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Avg merge
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Merged PRs (30d)
20

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