@pothos/plugin-sub-graph/src/util.ts

A Pothos plugin for creating multiple variants or sub-selections of the same graph

import { PothosSchemaError } from '@pothos/core';
import {
  GraphQLList,
  type GraphQLNamedType,
  GraphQLNonNull,
  type GraphQLNullableType,
  type GraphQLType,
} from 'graphql';

export function replaceType<T extends GraphQLType>(
  type: T,
  newTypes: Map<string, GraphQLNamedType>,
  referencedBy: string,
  subGraphs: string[],
): T {
  if (type instanceof GraphQLNonNull) {
    return new GraphQLNonNull(
      replaceType(type.ofType as GraphQLNullableType, newTypes, referencedBy, subGraphs),
    ) as T;
  }

  if (type instanceof GraphQLList) {
    return new GraphQLList(replaceType(type.ofType, newTypes, referencedBy, subGraphs)) as T;
  }

  const newType = newTypes.get((type as GraphQLNamedType).name);

  if (!newType) {
    throw new PothosSchemaError(
      `${
        (type as GraphQLNamedType).name
      } (referenced by ${referencedBy}) does not exist in subGraph (${subGraphs})`,
    );
  }

  return newType as T;
}