Schema

A schema names a shape of data and checks values against it. You pass the name and a Standard Schema to Schema. parse returns the schema’s output, or throws when the value does not fit.

class PostSchema extends Schema('Post', postSchema) {}

Zod, Valibot, ArkType, and any other Standard Schema library are passed straight through. @hexok/typebox adapts a TypeBox 1 schematic into a Standard Schema first.

Why it exists

A post is an id, a title, a body, and a published flag. That shape shows up on the entity, on the event that says the post was published, and at the edge where a request body arrives. One named schema is the definition those sites share. The name is what appears in the failure message, so a rejected post is distinguishable from a rejected subscriber.

How it’s used

Define the post once. The entity and the published-post event both take PostSchema. At a trust boundary, parse turns unknown JSON into the typed output.

const post = PostSchema.parse({
  id: 'p1',
  title: 'Hello',
  body: 'First post',
  published: false,
})

post.title is a string because the schema says so. A missing title throws a coded error whose code is VALIDATION and whose message is hexok: Post validation failed.

An entity or an event can also take the Standard Schema directly, without this class. Reach for Schema when you want the name, parse, and a place to customize the check.

API

Schema(token, definition) returns the class you extend. token is a string literal. definition is a Standard Schema.

Member	Role
PostSchema.token	The name you passed in.
PostSchema.definition	The Standard Schema this class wraps.
PostSchema.parse(value)	Check value and return the schema output.
PostSchema.check(value)	The same check. Overrides of parse call this when they want the default result.

A rejected value throws CodedError with code VALIDATION. data.issues is the Standard Schema issue list when the schema reported one. Each issue has a message and an optional path.

Override parse to preprocess or postprocess. Override check when the check itself should change.

schemaDefinition(schema) reads the Standard Schema out of either a Schema class or a raw Standard Schema. InferSchema<S> is the output type of either form. An async schema throws Error with the message hexok: async schemas belong at the application edge.