Function fromJSONSchema

packages/zod/src/v4/classic/from-json-schema.ts:629–659

(schema: JSONSchema.JSONSchema | boolean, params?: FromJSONSchemaParams)

/**
 * Converts a JSON Schema to a Zod schema. This function should be considered semi-experimental. It's behavior is liable to change. */
export function fromJSONSchema(schema: JSONSchema.JSONSchema | boolean, params?: FromJSONSchemaParams): ZodType {
  // Handle boolean schemas
  if (typeof schema === "boolean") {
    return schema ? z.any() : z.never();
  }

  // Normalize input via a JSON round-trip. This guarantees the converter
  // walks a plain, finite, JSON-valid object graph: cyclic inputs fail here,
  // getter/Proxy-based properties are materialized into static values, and
  // class instances collapse to plain objects.
  let normalized: JSONSchema.JSONSchema;
  try {
    normalized = JSON.parse(JSON.stringify(schema));
  } catch {
    throw new Error("fromJSONSchema input is not valid JSON (possibly cyclic); use $defs/$ref for recursive schemas");
  }

  const version = detectVersion(normalized, params?.defaultTarget);
  const defs = (normalized.$defs || normalized.definitions || {}) as Record<string, JSONSchema.JSONSchema>;

  const ctx: ConversionContext = {
    version,
    defs,
    refs: new Map(),
    processing: new Set(),
    rootSchema: normalized,
    registry: params?.registry ?? globalRegistry,
  };

  return convertSchema(normalized, ctx);
}