Method prepareFields

packages/sql/src/query/QueryBuilder.ts:3143–3256

(
    fields: InternalField<T>[],
    type: 'where' | 'groupBy' | 'sub-query' = 'where',
    schema?: string,
  )

  }

  protected prepareFields<T>(
    fields: InternalField<T>[],
    type: 'where' | 'groupBy' | 'sub-query' = 'where',
    schema?: string,
  ): (string | RawQueryFragment)[] {
    const ret: InternalField<T>[] = [];
    const getFieldName = (name: string, customAlias?: string) => {
      const alias = customAlias ?? (type === 'groupBy' ? null : undefined);
      return this.helper.mapper(name, this.type, undefined, alias, schema);
    };

    fields.forEach(originalField => {
      if (typeof originalField !== 'string') {
        ret.push(originalField);
        return;
      }

      // Strip 'as alias' suffix if present — the alias is passed to mapper at the end
      let field = originalField;
      let customAlias: string | undefined;
      const asMatch = FIELD_ALIAS_RE.exec(originalField);

      if (asMatch) {
        field = asMatch[1].trim();
        customAlias = asMatch[2];
      }

      const join = Object.keys(this.#state.joins).find(k => field === k.substring(0, k.indexOf('#')))!;

      if (join && type === 'where') {
        ret.push(...(this.helper.mapJoinColumns(this.type, this.#state.joins[join]) as string[]));
        return;
      }

      const [a, f] = this.helper.splitField(field as EntityKey<T>);
      const prop = this.helper.getProperty(f, a);

      /* v8 ignore next */
      if (prop && [ReferenceKind.ONE_TO_MANY, ReferenceKind.MANY_TO_MANY].includes(prop.kind)) {
        return;
      }

      if (prop?.persist === false && !prop.embedded && !prop.formula && type === 'where') {
        return;
      }

      if (prop?.embedded || (prop?.kind === ReferenceKind.EMBEDDED && prop.object)) {
        const name = prop.embeddedPath?.join('.') ?? prop.fieldNames[0];
        const aliased = this.#state.aliases[a] ? `${a}.${name}` : name;
        ret.push(getFieldName(aliased, customAlias));
        return;
      }

      if (prop?.kind === ReferenceKind.EMBEDDED) {
        if (customAlias) {
          throw new Error(
            `Cannot use 'as ${customAlias}' alias on embedded property '${field}' because it expands to multiple columns. Alias individual fields instead (e.g. '${field}.propertyName as ${customAlias}').`,
          );