Derive

derive.ts — re-exported from the package root — is not a projector. These are pure structural TypeRef => TypeRef transforms, the primitives everything else in fractal's codegen builds on (a projector never needs its own partial/pick/omit logic; it composes these instead). All of them pass non-object refs through unchanged unless noted, and none mutate their input.

import { partial, required, pick, omit, extend, nullable, withMeta, deepPartial, deepRequired } from "@rhi-zone/fractal-type-ir"

partial

All fields become optional (meta.optional = true).

const before = t(types.object({ id: t(types.integer), name: t(types.string) }))
partial(before)
// t(types.object({
//   id: t(types.integer, { optional: true }),
//   name: t(types.string, { optional: true }),
// }))

required

Inverse of partial — removes meta.optional from every field.

const before = t(types.object({ id: t(types.integer, { optional: true }) }))
required(before)
// t(types.object({ id: t(types.integer) }))

pick

Keep only the named fields; missing keys are silently skipped.

const before = t(types.object({ id: t(types.integer), name: t(types.string), email: t(types.string) }))
pick(before, ["id", "name"])
// t(types.object({ id: t(types.integer), name: t(types.string) }))

omit

Drop the named fields; missing keys are silently skipped.

const before = t(types.object({ id: t(types.integer), name: t(types.string), email: t(types.string) }))
omit(before, ["email"])
// t(types.object({ id: t(types.integer), name: t(types.string) }))

extend

Merge two object TypeRefs — extension fields (and meta) override base fields with the same name, last-write-wins. If either side isn't an object, the extension wins outright (no error).

const base = t(types.object({ id: t(types.integer), name: t(types.string) }))
const extension = t(types.object({ name: t(types.string, { minLength: 1 }), email: t(types.string) }))
extend(base, extension)
// t(types.object({
//   id: t(types.integer),
//   name: t(types.string, { minLength: 1 }),
//   email: t(types.string),
// }))

nullable

Sets meta.nullable = true on the ref.

const before = t(types.string)
nullable(before)
// t(types.string, { nullable: true })

withMeta

Merge additional metadata into a TypeRef (constraints, descriptions, etc.).

const before = t(types.integer)
withMeta(before, { minimum: 0, description: "must be non-negative" })
// t(types.integer, { minimum: 0, description: "must be non-negative" })

deepPartial

Like partial, but recurses into nested object fields (and object elements of arrays/streams/pages), making every level optional. Non-object leaf fields just get meta.optional = true. Cycle-safe — a shape already visited is returned as-is rather than reprocessed.

const before = t(types.object({
  id: t(types.integer),
  address: t(types.object({ city: t(types.string) })),
}))
deepPartial(before)
// t(types.object({
//   id: t(types.integer, { optional: true }),
//   address: t(types.object({
//     city: t(types.string, { optional: true }),
//   }), { optional: true }),
// }))

deepRequired

Inverse of deepPartial — recurses into nested object fields (and object elements of arrays/streams/pages), removing meta.optional at every level. Cycle-safe like deepPartial.

const before = t(types.object({
  id: t(types.integer, { optional: true }),
  address: t(types.object({ city: t(types.string, { optional: true }) }), { optional: true }),
}))
deepRequired(before)
// t(types.object({
//   id: t(types.integer),
//   address: t(types.object({ city: t(types.string) })),
// }))