strapi/packages/plugins/graphql/server/services/builders/resolvers/association.js

'use strict';

const { omit } = require('lodash/fp');

const { transformArgs } = require('../utils');
const { utils } = require('../../types');

module.exports = ({ strapi }) => ({
  buildAssociationResolver: ({ contentTypeUID, attributeName }) => {
    const { entityManager } = strapi.db;

    const contentType = strapi.getModel(contentTypeUID);
    const attribute = contentType.attributes[attributeName];

    if (!attribute) {
      throw new Error(
        `Failed to build an association resolver for ${contentTypeUID}::${attributeName}`
      );
    }

    const isMedia = utils.isMedia(attribute);
    const isMorph = utils.isMorphRelation(attribute);

    const targetUID = isMedia ? 'plugins::upload.file' : attribute.target;
    const isToMany = isMedia ? attribute.multiple : attribute.relation.endsWith('Many');

    const targetContentType = strapi.getModel(targetUID);

    return async (source, args = {}) => {
      const transformedArgs = transformArgs(args, {
        contentType: targetContentType,
        usePagination: true,
      });

      // Since we're using the entity-manager & not the entity-service to load the
      // association, we need to apply some transformation to the transformed args object
      const entityManagerArgs = {
        ...omit(['start', 'filters'], transformedArgs),
        where: transformedArgs.filters,
        offset: transformedArgs.start,
      };

      // todo[v4]: should we move the .load to the entity service so we can use the same args everywhere?
      const data = await entityManager.load(
        contentTypeUID,
        source,
        attributeName,
        entityManagerArgs
      );

      // If this a polymorphic association, it returns the raw data
      if (isMorph) {
        return data;
      }

      // If this is a to-many relation, it returns an object that
      // matches what the entity-response-collection's resolvers expect
      else if (isToMany) {
        return { nodes: data, info: { args: transformedArgs, resourceUID: targetUID } };
      }

      // Else, it returns an object that matches
      // what the entity-response's resolvers expect
      return { value: data };
    };
  },
});