Function extractDefs

packages/zod/src/v4/core/to-json-schema.ts:217–357

(
  ctx: ToJSONSchemaContext,
  schema: T
  // params: EmitParams
)

}

export function extractDefs<T extends schemas.$ZodType>(
  ctx: ToJSONSchemaContext,
  schema: T
  // params: EmitParams
): void {
  // iterate over seen map;
  const root = ctx.seen.get(schema);

  if (!root) throw new Error("Unprocessed schema. This is a bug in Zod.");

  // Track ids to detect duplicates across different schemas
  const idToSchema = new Map<string, schemas.$ZodType>();
  for (const entry of ctx.seen.entries()) {
    const id = ctx.metadataRegistry.get(entry[0])?.id;
    if (id) {
      const existing = idToSchema.get(id);
      if (existing && existing !== entry[0]) {
        throw new Error(
          `Duplicate schema id "${id}" detected during JSON Schema conversion. Two different schemas cannot share the same id when converted together.`
        );
      }
      idToSchema.set(id, entry[0]);
    }
  }

  // returns a ref to the schema
  // defId will be empty if the ref points to an external schema (or #)
  const makeURI = (entry: [schemas.$ZodType<unknown, unknown>, Seen]): { ref: string; defId?: string } => {
    // comparing the seen objects because sometimes
    // multiple schemas map to the same seen object.
    // e.g. lazy

    // external is configured
    const defsSegment = ctx.target === "draft-2020-12" ? "$defs" : "definitions";
    if (ctx.external) {
      const externalId = ctx.external.registry.get(entry[0])?.id; // ?? "__shared";// `__schema${ctx.counter++}`;

      // check if schema is in the external registry
      const uriGenerator = ctx.external.uri ?? ((id: string) => id);
      if (externalId) {
        return { ref: uriGenerator(externalId) };
      }

      // otherwise, add to __shared
      const id: string = entry[1].defId ?? (entry[1].schema.id as string) ?? `schema${ctx.counter++}`;
      entry[1].defId = id; // set defId so it will be reused if needed
      return { defId: id, ref: `${uriGenerator("__shared")}#/${defsSegment}/${id}` };
    }

    if (entry[1] === root) {
      return { ref: "#" };
    }

    // self-contained schema
    const uriPrefix = `#`;
    const defUriPrefix = `${uriPrefix}/${defsSegment}/`;
    const defId = entry[1].schema.id ?? `__schema${ctx.counter++}`;
    return { defId, ref: defUriPrefix + defId };