Function _transform

ark/schema/node.ts:516–610

(
		mapper: DeepNodeTransformation,
		ctx: DeepNodeTransformContext
	)

	}

	protected _transform(
		mapper: DeepNodeTransformation,
		ctx: DeepNodeTransformContext
	): BaseNode | null {
		const $ = ctx.bindScope ?? this.$
		if (ctx.seen[this.id])
			// Cyclic handling needs to be made more robust
			// https://github.com/arktypeio/arktype/issues/944
			return this.$.lazilyResolve(ctx.seen[this.id]! as never)
		if (ctx.shouldTransform?.(this as never, ctx) === false) return this

		let transformedNode: BaseRoot | undefined

		ctx.seen[this.id] = () => transformedNode

		if (
			this.hasKind("structure") &&
			this.undeclared !== ctx.undeclaredKeyHandling
		) {
			ctx = {
				...ctx,
				undeclaredKeyHandling: this.undeclared
			}
		}

		const innerWithTransformedChildren = flatMorph(
			this.inner as Dict,
			(k, v) => {
				if (!this.impl.keys[k].child) return [k, v]
				const children = v as listable<BaseNode>
				if (!isArray(children)) {
					const transformed = children._transform(mapper, ctx)
					return transformed ? [k, transformed] : []
				}
				// if the value was previously explicitly set to an empty list,
				// (e.g. branches for `never`), ensure it is not pruned
				if (children.length === 0) return [k, v]
				const transformed = children.flatMap(n => {
					const transformedChild = n._transform(mapper, ctx)
					return transformedChild ?? []
				})
				return transformed.length ? [k, transformed] : []
			}
		)

		delete ctx.seen[this.id]

		const innerWithMeta = Object.assign(innerWithTransformedChildren, {
			meta: this.meta
		})

		const transformedInner =
			ctx.selected && !ctx.selected.includes(this) ?
				innerWithMeta
			:	mapper(this.kind, innerWithMeta, ctx)

		if (transformedInner === null) return null