Function mapJoinedProps

packages/sql/src/AbstractSqlDriver.ts:591–798

(
    result: EntityData<T>,
    meta: EntityMetadata<T>,
    populate: PopulateOptions<T>[],
    qb: AnyQueryBuilder<T>,
    root: EntityData<T>,
    map: Dictionary,
    parentJoinPath?: string,
  )

  }

  private mapJoinedProps<T extends object>(
    result: EntityData<T>,
    meta: EntityMetadata<T>,
    populate: PopulateOptions<T>[],
    qb: AnyQueryBuilder<T>,
    root: EntityData<T>,
    map: Dictionary,
    parentJoinPath?: string,
  ) {
    const joinedProps = this.joinedProps(meta, populate);

    joinedProps.forEach(hint => {
      const [propName, ref] = hint.field.split(':', 2) as [EntityKey<T>, string | undefined];
      const prop = meta.properties[propName];

      /* v8 ignore next */
      if (!prop) {
        return;
      }

      // Polymorphic to-one: iterate targets, find the matching one, build entity from its columns.
      // Skip :ref hints — no JOINs were created, so the FK reference is already set by the result mapper.
      if (
        prop.polymorphic &&
        prop.polymorphTargets?.length &&
        !ref &&
        [ReferenceKind.MANY_TO_ONE, ReferenceKind.ONE_TO_ONE].includes(prop.kind)
      ) {
        const basePath = parentJoinPath ? `${parentJoinPath}.${prop.name}` : `${meta.name}.${prop.name}`;
        const pathPrefix = !parentJoinPath ? '[populate]' : '';
        let matched = false;

        for (const targetMeta of prop.polymorphTargets) {
          const targetPath = `${pathPrefix}${basePath}[${targetMeta.className}]`;
          const relationAlias = qb.getAliasForJoinPath(targetPath, { matchPopulateJoins: true })!;
          const meta2 = targetMeta as EntityMetadata<T>;
          const targetProps = meta2.props.filter(p => this.platform.shouldHaveColumn(p, (hint.children as any) || []));

          const hasPK = meta2
            .getPrimaryProps()
            .every(pk => pk.fieldNames.every(name => root[`${relationAlias}__${name}` as EntityKey] != null));

          if (hasPK && !matched) {
            matched = true;
            const relationPojo: EntityData<T> = {};
            const tz = this.platform.getTimezone();

            for (const p of targetProps) {
              this.mapJoinedProp(relationPojo, p, relationAlias, root, tz, meta2);
            }

            // For TPT base targets, map child-specific fields and resolve the
            // concrete class so the factory creates the correct subtype.
            const concreteMeta = this.mapTPTChildFields(relationPojo, meta2, relationAlias, qb, root);

            Object.defineProperty(relationPojo, 'constructor', {
              value: concreteMeta?.class ?? meta2.class,
              enumerable: false,