Add support for using promises in Cursor methods (brianc#2554)

* Add similar promise variables to read() and close() as seen in query() * Add testing for promise specific usage * Simplify tests as no real callbacks are involved Removes usage of `done()` since we can end the test when we exit the function Co-Authored-By: Charmander <~@charmander.me> * Switch to let over var Co-authored-by: Charmander <~@charmander.me>

Author: Bluenix2

packages/pg-cursor/index.js

@@ -17,6 +17,7 @@ class Cursor extends EventEmitter {
  this._queue = []
  this.state = 'initialized'
  this._result = new Result(this._conf.rowMode, this._conf.types)
+ this._Promise = this._conf.Promise || global.Promise
  this._cb = null
  this._rows = null
  this._portal = null
@@ -198,6 +199,14 @@ class Cursor extends EventEmitter {
  }
 
  close(cb) {
+ let promise
+
+ if (!cb) {
+ promise = new this._Promise((resolve, reject) => {
+ cb = (err) => (err ? reject(err) : resolve())
+ })
+ }
+
  if (!this.connection || this.state === 'done') {
  if (cb) {
  return setImmediate(cb)
@@ -213,23 +222,34 @@ class Cursor extends EventEmitter {
  cb()
  })
  }
+
+ // Return the promise (or undefined)
+ return promise
  }
 
  read(rows, cb) {
- if (this.state === 'idle' || this.state === 'submitted') {
- return this._getRows(rows, cb)
- }
- if (this.state === 'busy' || this.state === 'initialized') {
- return this._queue.push([rows, cb])
- }
- if (this.state === 'error') {
- return setImmediate(() => cb(this._error))
+ let promise
+
+ if (!cb) {
+ promise = new this._Promise((resolve, reject) => {
+ cb = (err, rows) => (err ? reject(err) : resolve(rows))
+ })
  }
- if (this.state === 'done') {
- return setImmediate(() => cb(null, []))
+
+ if (this.state === 'idle' || this.state === 'submitted') {
+ this._getRows(rows, cb)
+ } else if (this.state === 'busy' || this.state === 'initialized') {
+ this._queue.push([rows, cb])
+ } else if (this.state === 'error') {
+ setImmediate(() => cb(this._error))
+ } else if (this.state === 'done') {
+ setImmediate(() => cb(null, []))
  } else {
  throw new Error('Unknown state: ' + this.state)
  }
+
+ // Return the promise (or undefined)
+ return promise
  }
 }
 

packages/pg-cursor/test/promises.js

@@ -0,0 +1,51 @@
+const assert = require('assert')
+const Cursor = require('../')
+const pg = require('pg')
+
+const text = 'SELECT generate_series as num FROM generate_series(0, 5)'
+
+describe('cursor using promises', function () {
+ beforeEach(function (done) {
+ const client = (this.client = new pg.Client())
+ client.connect(done)
+
+ this.pgCursor = function (text, values) {
+ return client.query(new Cursor(text, values || []))
+ }
+ })
+
+ afterEach(function () {
+ this.client.end()
+ })
+
+ it('resolve with result', async function () {
+ const cursor = this.pgCursor(text)
+ const res = await cursor.read(6)
+ assert.strictEqual(res.length, 6)
+ })
+
+ it('reject with error', function (done) {
+ const cursor = this.pgCursor('select asdfasdf')
+ cursor.read(1).error((err) => {
+ assert(err)
+ done()
+ })
+ })
+
+ it('read multiple times', async function () {
+ const cursor = this.pgCursor(text)
+ let res
+
+ res = await cursor.read(2)
+ assert.strictEqual(res.length, 2)
+
+ res = await cursor.read(3)
+ assert.strictEqual(res.length, 3)
+
+ res = await cursor.read(1)
+ assert.strictEqual(res.length, 1)
+
+ res = await cursor.read(1)
+ assert.strictEqual(res.length, 0)
+ })
+})