@teamstarter/graphql-sequelize-generator/src/removeUnusedAttributes.ts

A set of tools to easily generate a Graphql API from sequelize models.

import { simplifyAST } from 'graphql-sequelize'
import { FindOptions, Model, ModelStatic } from 'sequelize'
import { SequelizeModels, TInfo } from './types/types'

/**
 * This functions returns the findOptions for a findAll/One with only the attributes required in the info.
 * By default all attributes are always fetched.
 *
 * @param {*} findOptions
 * @param {*} info
 * @param {Array<string>} keep An array of all the attributes to keep
 */
export default function removeUnusedAttributes<M extends Model<any>>(
  findOptions: FindOptions<M>,
  info: TInfo,
  currentModel: ModelStatic<M>,
  models: SequelizeModels,
  keep: Array<string> = []
): FindOptions {
  const { fieldNodes } = info
  if (!fieldNodes) {
    return findOptions
  }
  const ast = simplifyAST(fieldNodes[0], info)

  const linkFields: any = []
  /**
   * This reduce is made to add the attributes required to fetch
   * sub objects. This part of the code not responsible for the parents.
   * For exemple if the "id" of car is not selected, it will not be handled here
   * but on the next step.
   *
   * Example :
   * user {
   *   id
   *   // carId
   *   car {
   *     id
   *   }
   * }
   *
   * If carId is not asked in the GraphQL query, we must still include it so
   * that the reconcilier can match the car with the user.
   *
   */
  const attributes = Object.keys(ast.fields).filter((attribute) => {
    // The typename field is a key metadata and must always be returned if asked
    if (attribute === '__typename') {
      return false
    }
    // We check if the field is a leef or an entity
    if (Object.keys(ast.fields[attribute].fields).length > 0) {
      // If the field is an entity we check if we find the association
      if (models[currentModel.name].associations[attribute]) {
        const association: any =
          models[currentModel.name].associations[attribute]
        // If so we add the foreignKey to the list of fields to fetch.
        // Without it the sub-entities will not be fetched
        if (
          ['HasOne', 'HasMany', 'BelongsToMany'].includes(
            association.associationType
          )
        ) {
          linkFields.push(association.sourceKey)
        } else if (['BelongsTo'].includes(association.associationType)) {
          linkFields.push(association.foreignKey)
        } else {
          throw new Error(
            `removeUnusedAttributes does not support his association: ${association.associationType} for entity ${currentModel.name}/${association.as}`
          )
        }
      }
      // In any case, the entity name as attribute is not returned.
      return false
    }
    return true
  })

  /**
   * This part of the code is in charge of adding information required to be fetched
   * to match with the parent object.
   *
   * Example :
   * user {
   *   id
   *   cars {
   *     id
   *     // userId
   *   }
   * }
   *
   * If userId is not asked in the GraphQL query, we must still include it so
   * that the reconcilier can match the cars with the user.
   *
   */
  const parentModelReferenceAttributes: string[] = []
  // The relation can be direct
  if (currentModel.associations[info.parentType.name]) {
    if (
      currentModel.associations[info.parentType.name].associationType ===
      'BelongsTo'
    ) {
      parentModelReferenceAttributes.push(
        currentModel.associations[info.parentType.name].foreignKey
      )
    }
    // @todo add more cases as they are used
  }
  // Or indirect
  if (
    models[info.parentType.name] &&
    models[info.parentType.name].associations[info.fieldName]
  ) {
    if (
      ['HasMany', 'HasOne'].includes(
        models[info.parentType.name].associations[info.fieldName]
          .associationType
      )
    ) {
      parentModelReferenceAttributes.push(
        models[info.parentType.name].associations[info.fieldName].foreignKey
      )
    }
    // @todo add more cases as they are used
  }

  return {
    ...findOptions,
    attributes: [
      ...new Set([
        ...attributes,
        ...linkFields,
        ...parentModelReferenceAttributes,
        ...keep,
      ]),
    ],
  }
}