@sap/cds/libx/_runtime/common/generic/crud.js

SAP Cloud Application Programming Model - CDS for Node.js

const cds = require('../../cds')
const { SELECT } = cds.ql

module.exports = exports = cds.service.impl(function () {
  // prettier-ignore
  this.on(['CREATE', 'READ', 'UPDATE', 'UPSERT', 'DELETE'], '*', async function handle_crud_requests(req) {
    if (!cds.db)
      return req.reject('NO_DATABASE_CONNECTION') // REVISIT: error message
    if (!req.query)
      return req.reject(501, 'The request has no query and cannot be served generically.')
    if (req.target['@cds.persistence.skip'] === true && req.target['@cds.persistence.table'] !== true)
      return req.reject(501, `Entity "${req.target.name}" is annotated with "@cds.persistence.skip" and cannot be served generically.`)

    const { ref } = req.query.INSERT?.into || req.query.SELECT?.from || {}
    const check_parent = ref?.length > 1 ? SELECT.one(1).from({ ref: ref.slice(0, -1) }) : null
    if (check_parent && req.event === 'CREATE') (await check_parent) || req.reject(404)
    else if (req.target?._isSingleton) await handle_singleton_request(req)
    else if (req.query?.SELECT && req.locale) req.query.SELECT.localized ??= true

    // REVISIT for cds^10: can we always use cds.db.dispatch(req)?
    const result = req.iterator && !req.objectMode
      ? await cds.db.dispatch(req)
      : await cds.run(req.query, req.data)

    return await exports._handle_result(req, result, check_parent)
  })
})

async function handle_singleton_request(req) {
  if (req.event !== 'DELETE' && req.event !== 'UPDATE') return
  if (req.event === 'DELETE') req.target['@odata.singleton.nullable'] || req.reject(400, 'SINGLETON_NOT_NULLABLE')

  const fetch_singleton = SELECT.one(req.target)
  const keys = [...(req.target.keys || [])].filter(e => !e.isAssociation).map(e => e.name)
  // if no keys available, select all columns so we can delete the singleton with same content
  if (keys.length) fetch_singleton.columns(keys)
  const singleton = await fetch_singleton
  if (!singleton) throw req.reject(404)

  // REVISIT: Workaround for singleton, to get keys into singleton
  for (const k in singleton) if (keys.includes(k)) req.data[k] = singleton[k]
  req.query.where(singleton)
}

async function new_behavior(req, result, parent) {
  const n = result?.affected ?? result?.length ?? result

  // prettier-ignore
  switch (req.event) {
    case 'READ':
      if (!n && req._etagValidationType === 'if-match') req.reject(412)
      if (!n) !parent || (await parent) || req.reject(404)
      return result
    case 'INSERT': case 'CREATE':
      if (result.affected != null) return result //> db service returned [affected]
      else return Object.assign([...result], { affected: result.affectedRows })
    case 'UPSERT': case 'UPDATE': case 'DELETE':
      if (!n && req._etagValidationType) return req.reject(412)
      if (!n) (await cds.db.exists(req.subject)) || req.reject(404)
      if (result.affected != null) return result //> db service returned [affected]
      else return Object.assign([], { affected: n })
  }
}

async function legacy_behavior(req, result, parent) {
  if (req.event !== 'READ' && req.protocol?.match(/odata/)) req._.readAfterWrite = true

  const x = await new_behavior(req, result, parent)
  // prettier-ignore
  switch (req.event) {
    case 'READ': return x //> array of results or single result or null
    case 'DELETE': return x.affected //> number of deleted rows
    default: return req.data
  }
}

exports._handle_result = legacy_behavior
exports._always_return_arrays = on_off => {
  if (on_off === undefined) return exports._handle_result === new_behavior
  exports._handle_result = on_off ? new_behavior : legacy_behavior
}
exports._always_return_arrays(!cds.env.features.legacy_srv_results)