324 lines
14 KiB
TypeScript
324 lines
14 KiB
TypeScript
/**
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* Structured-output JSON Schema subset for subagents and workflows. It supports
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* one scalar `type`; object `properties`/`required`/boolean
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* `additionalProperties`; array `items`; scalar `enum`/`const`; and JSON-valued
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* annotations. Unsupported or misplaced keywords reject rather than being
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* accepted without enforcement, and structured-output roots must be objects.
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* @module dsh-tools/json-schema
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*/
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import { assertNever, HarnessError } from '@deepseek-ai/dsh-llm'
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/** The scalar values `enum`/`const` may carry (finite numbers only). */
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export type StructuredScalar = string | number | boolean | null
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/** The `type` keywords the subset accepts. */
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export type StructuredSchemaType = 'object' | 'array' | 'string' | 'number' | 'integer' | 'boolean' | 'null'
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/**
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* One node of the structured-output schema subset. Recursive via `properties`
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* and `items`; see the module doc for the exact keyword semantics.
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*/
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export interface StructuredSchemaNode {
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type: StructuredSchemaType
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/** Nested property schemas (`type: 'object'` only). */
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properties?: Record<string, StructuredSchemaNode>
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/** Required property names; each must appear in `properties`. */
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required?: string[]
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/** `false` rejects undeclared keys; absent/`true` allows them (JSON Schema default). */
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additionalProperties?: boolean
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/** Item schema (`type: 'array'` only); absent ⇒ any JSON items. */
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items?: StructuredSchemaNode
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/** Allowed values (scalar types only). */
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enum?: StructuredScalar[]
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/** The single allowed value (scalar types only). */
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const?: StructuredScalar
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/** Annotation, ignored for validation. */
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description?: string
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/** Annotation, ignored for validation. */
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title?: string
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/** Annotation, ignored for validation (must still be JSON data). */
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default?: unknown
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/** Annotation, ignored for validation (must still be JSON data). */
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examples?: unknown
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}
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/** A structured-output schema: an OBJECT-rooted {@link StructuredSchemaNode}. */
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export type StructuredOutputSchema = StructuredSchemaNode & { type: 'object' }
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/**
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* Thrown by {@link assertSupportedOutputSchema} when a schema falls outside the
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* supported subset. Extends {@link HarnessError} (`code: 'UNSUPPORTED_SCHEMA'`)
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* so seam code and tool results can route on it; `violations` lists every
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* offending path, not just the first.
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*/
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export class OutputSchemaError extends HarnessError {
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/** The individual violation messages, in walk order. */
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readonly violations: string[]
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constructor(violations: string[]) {
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super(`unsupported output schema: ${violations.join('; ')}`, 'UNSUPPORTED_SCHEMA')
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this.name = 'OutputSchemaError'
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this.violations = violations
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}
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}
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/** The keywords the subset accepts, checked (`constraint`) or ignored (`annotation`). */
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const CONSTRAINT_KEYWORDS = new Set(['type', 'properties', 'required', 'additionalProperties', 'items', 'enum', 'const'])
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const ANNOTATION_KEYWORDS = new Set(['description', 'title', 'default', 'examples'])
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const SCHEMA_TYPES: readonly StructuredSchemaType[] = ['object', 'array', 'string', 'number', 'integer', 'boolean', 'null']
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/**
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* Whether a value is a PLAIN JSON object — non-null, non-array, and with a
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* prototype chain of at most one link (`null`-proto, or any realm's
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* `Object.prototype`, whose own prototype is `null`). Realm-agnostic on
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* purpose: a schema materialized in another realm carries THAT realm's
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* `Object.prototype`, which an identity check would wrongly reject. Exotic
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* hosts (`Date`, `Map`, class instances) have longer chains and are rejected —
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* they would serialize lossily (`Date` → string, `Map` → `{}`) instead of
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* failing loud.
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*/
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function isObjectLike(value: unknown): value is Record<string, unknown> {
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if (typeof value !== 'object' || value === null || Array.isArray(value)) return false
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const proto: unknown = Object.getPrototypeOf(value)
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return proto === null || Object.getPrototypeOf(proto) === null
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}
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/** Whether a value is a supported scalar (`enum`/`const` member): string, finite number, boolean, or null. */
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function isStructuredScalar(value: unknown): value is StructuredScalar {
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return value === null || typeof value === 'string' || typeof value === 'boolean'
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|| (typeof value === 'number' && Number.isFinite(value))
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}
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/**
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* Whether a value is JSON data (annotation payloads only): scalars, arrays, and
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* object-likes of such values. Realm-agnostic on purpose (no prototype check) —
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* the schema may have been materialized from another realm; structural JSON-ness
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* is what the wire needs. Cycles are rejected via `seen`.
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*/
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function isJsonData(value: unknown, seen: Set<object>): boolean {
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if (isStructuredScalar(value)) return true
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// The scalar check above already returned for null, so `object` here is a real object.
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if (typeof value !== 'object') return false
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if (seen.has(value)) return false
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seen.add(value)
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try {
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if (Array.isArray(value)) return value.every(entry => isJsonData(entry, seen))
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// A non-plain object (Date, Map, class instance) is NOT JSON data even when
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// it has no enumerable values — it would serialize lossily, not loudly.
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if (!isObjectLike(value)) return false
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return Object.values(value).every(entry => isJsonData(entry, seen))
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} finally {
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seen.delete(value)
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}
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}
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/** Collect subset violations for one schema node (recursive walk). */
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function checkSchemaNode(node: unknown, path: string, violations: string[], seen: Set<object>): void {
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if (!isObjectLike(node)) {
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violations.push(`${path} must be a schema object`)
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return
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}
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if (seen.has(node)) {
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violations.push(`${path} is circular`)
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return
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}
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seen.add(node)
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for (const key of Object.keys(node)) {
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if (CONSTRAINT_KEYWORDS.has(key)) continue
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if (ANNOTATION_KEYWORDS.has(key)) {
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if (!isJsonData(node[key], new Set())) violations.push(`${path}.${key} annotation must be JSON data`)
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continue
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}
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violations.push(`${path}.${key} is not a supported keyword (subset: type/properties/required/additionalProperties/items/enum/const + annotations)`)
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}
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if (typeof node.description !== 'undefined' && typeof node.description !== 'string') {
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violations.push(`${path}.description must be a string`)
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}
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if (typeof node.title !== 'undefined' && typeof node.title !== 'string') {
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violations.push(`${path}.title must be a string`)
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}
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const type = node.type
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if (typeof type !== 'string' || !(SCHEMA_TYPES as readonly unknown[]).includes(type)) {
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violations.push(Array.isArray(type)
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? `${path}.type must be a single type string (type arrays are not supported)`
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: `${path}.type must be one of ${SCHEMA_TYPES.join('/')}`)
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seen.delete(node)
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return
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}
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const schemaType = type as StructuredSchemaType
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// Keywords that only make sense on one type are rejected elsewhere — an
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// `items` on an object (or `properties` on a string) is a schema-author bug
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// the subset surfaces rather than ignores.
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const allowedFor: Record<string, StructuredSchemaType[]> = {
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properties: ['object'],
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required: ['object'],
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additionalProperties: ['object'],
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items: ['array'],
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enum: ['string', 'number', 'integer', 'boolean', 'null'],
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const: ['string', 'number', 'integer', 'boolean', 'null'],
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}
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for (const [key, types] of Object.entries(allowedFor)) {
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if (key in node && !types.includes(schemaType)) {
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violations.push(`${path}.${key} is not supported on type "${schemaType}"`)
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}
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}
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switch (schemaType) {
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case 'object': {
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const properties = node.properties
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if (properties !== undefined) {
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if (!isObjectLike(properties)) {
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violations.push(`${path}.properties must be an object of schemas`)
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} else {
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for (const [key, child] of Object.entries(properties)) {
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checkSchemaNode(child, `${path}.properties.${key}`, violations, seen)
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}
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}
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}
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const required = node.required
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if (required !== undefined) {
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if (!Array.isArray(required) || required.some(entry => typeof entry !== 'string')) {
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violations.push(`${path}.required must be an array of strings`)
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} else {
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const declared = isObjectLike(properties) ? properties : {}
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// The guard above proved every entry is a string.
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for (const key of required as string[]) {
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// Own-property check: `in` would let inherited names (`toString`)
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// satisfy the declared-in-properties contract via the prototype.
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if (!Object.hasOwn(declared, key)) violations.push(`${path}.required names "${key}" which is not in properties`)
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}
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}
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}
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if (node.additionalProperties !== undefined && typeof node.additionalProperties !== 'boolean') {
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violations.push(`${path}.additionalProperties must be a boolean`)
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}
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break
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}
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case 'array': {
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if (node.items !== undefined) checkSchemaNode(node.items, `${path}.items`, violations, seen)
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break
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}
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case 'string':
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case 'number':
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case 'integer':
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case 'boolean':
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case 'null': {
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const allowed = node.enum
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if (allowed !== undefined) {
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if (!Array.isArray(allowed) || allowed.length === 0 || !allowed.every(entry => isStructuredScalar(entry))) {
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violations.push(`${path}.enum must be a non-empty array of scalars`)
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}
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}
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if ('const' in node && !isStructuredScalar(node.const)) {
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violations.push(`${path}.const must be a scalar`)
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}
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break
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}
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/* v8 ignore start -- defensive: schemaType was membership-checked against SCHEMA_TYPES above, so no runtime value reaches here */
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default:
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assertNever(schemaType, 'assertSupportedOutputSchema')
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/* v8 ignore stop */
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}
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seen.delete(node)
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}
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/**
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* Assert `schema` is a supported {@link StructuredOutputSchema} — object-rooted
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* and entirely within the enforced subset. Throws {@link OutputSchemaError}
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* (`UNSUPPORTED_SCHEMA`) listing EVERY violation; returns (and narrows) on
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* success. Call this at the seam boundary, before any child is created.
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* @param schema - the caller-supplied schema (unknown until asserted).
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* @returns nothing — the assertion signature narrows `schema` to
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* {@link StructuredOutputSchema} in the caller's scope on normal return.
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*/
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export function assertSupportedOutputSchema(schema: unknown): asserts schema is StructuredOutputSchema {
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const violations: string[] = []
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checkSchemaNode(schema, 'schema', violations, new Set())
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if (violations.length === 0 && (schema as StructuredSchemaNode).type !== 'object') {
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violations.push('schema.type must be "object" (structured output is object-rooted)')
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}
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if (violations.length > 0) throw new OutputSchemaError(violations)
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}
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/** Collect violations for one value against an (already asserted) schema node. */
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function checkValue(node: StructuredSchemaNode, value: unknown, path: string): string[] {
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switch (node.type) {
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case 'object': {
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if (!isObjectLike(value)) return [`"${path}" must be an object`]
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const violations: string[] = []
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const properties = node.properties ?? {}
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// Own-property discipline throughout: JSON carries own enumerable
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// properties only, so an inherited `toString` must not satisfy
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// `required`, dodge `additionalProperties: false`, or be validated as if
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// the value carried it.
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for (const key of node.required ?? []) {
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if (!Object.hasOwn(value, key) || value[key] === undefined) violations.push(`missing required property "${path}.${key}"`)
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}
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for (const [key, child] of Object.entries(properties)) {
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if (!Object.hasOwn(value, key) || value[key] === undefined) continue
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violations.push(...checkValue(child, value[key], `${path}.${key}`))
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}
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if (node.additionalProperties === false) {
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for (const key of Object.keys(value)) {
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if (!Object.hasOwn(properties, key)) violations.push(`"${path}.${key}" is not a declared property (additionalProperties: false)`)
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}
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}
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return violations
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}
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case 'array': {
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if (!Array.isArray(value)) return [`"${path}" must be an array`]
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if (!node.items) return []
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const items = node.items
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return value.flatMap((entry, index) => checkValue(items, entry, `${path}[${index}]`))
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}
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case 'string': {
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if (typeof value !== 'string') return [`"${path}" must be a string`]
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break
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}
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case 'number': {
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if (typeof value !== 'number' || !Number.isFinite(value)) return [`"${path}" must be a finite number`]
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break
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}
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case 'integer': {
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if (typeof value !== 'number' || !Number.isInteger(value)) return [`"${path}" must be an integer`]
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break
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}
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case 'boolean': {
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if (typeof value !== 'boolean') return [`"${path}" must be a boolean`]
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break
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}
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case 'null': {
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if (value !== null) return [`"${path}" must be null`]
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break
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}
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default:
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return assertNever(node.type, 'validateStructuredValue')
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}
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// Scalar constraint checks, shared by every scalar branch above.
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if (node.enum && !node.enum.includes(value)) {
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return [`"${path}" must be one of ${JSON.stringify(node.enum)}`]
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}
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if ('const' in node && value !== node.const) {
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return [`"${path}" must be ${JSON.stringify(node.const)}`]
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}
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return []
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}
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/**
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* Validate a value against an (already {@link assertSupportedOutputSchema}-
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* asserted) schema. Returns human-readable, path-qualified violation messages
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* — empty means valid. Total: never throws, however malformed the value.
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* @param schema - the asserted schema to check against.
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* @param value - the candidate value (e.g. parsed tool-call arguments).
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* @returns every violation found, in walk order (empty = valid).
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*/
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export function validateStructuredValue(schema: StructuredOutputSchema, value: unknown): string[] {
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return checkValue(schema, value, 'value')
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}
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