refactor: use native Promise instead of Bluebird (#3436)

All supported Node versions support native promises and async/await, current code has a minimal usage of Bluebird-specific methods, so dropping a third-party library in favor of native Promises.

Tests were using `Promise.setScheduler()` from Bluebird, which allowed to customize how Promises are scheduled and made test work very different from the real code, which created tricky issues (like #3060 (comment)). Affected tests were updated to not rely on `Promise.setScheduler()`, which improved readability in some situations. Also removed some test helpers as they are not necessary and not used anymore.

BREAKING CHANGE: Karma plugins which rely on the fact that Karma uses Bluebird promises may break as Bluebird-specific API is no longer available on Promises returned by the Karma core

lib/file-list.js

@@ -1,9 +1,10 @@
 'use strict'
 
-const Promise = require('bluebird')
+const { promisify } = require('util')
 const mm = require('minimatch')
 const Glob = require('glob').Glob
-const fs = Promise.promisifyAll(require('graceful-fs'))
+const fs = require('graceful-fs')
+fs.statAsync = promisify(fs.stat)
 const pathLib = require('path')
 const _ = require('lodash')
 
@@ -60,8 +61,8 @@ class FileList {
     const matchedFiles = new Set()
 
     let lastCompletedRefresh = this._refreshing
-    lastCompletedRefresh = Promise
-      .map(this._patterns, async ({ pattern, type, nocache, isBinary }) => {
+    lastCompletedRefresh = Promise.all(
+      this._patterns.map(async ({ pattern, type, nocache, isBinary }) => {
         if (helper.isUrlAbsolute(pattern)) {
           this.buckets.set(pattern, [new Url(pattern, type)])
           return
@@ -86,7 +87,7 @@ class FileList {
         if (nocache) {
           log.debug(`Not preprocessing "${pattern}" due to nocache`)
         } else {
-          await Promise.map(files, (file) => this._preprocess(file))
+          await Promise.all(files.map((file) => this._preprocess(file)))
         }
 
         this.buckets.set(pattern, files)
@@ -97,6 +98,7 @@ class FileList {
           log.warn(`All files matched by "${pattern}" were excluded or matched by prior matchers.`)
         }
       })
+    )
       .then(() => {
         // When we return from this function the file processing chain will be
         // complete. In the case of two fast refresh() calls, the second call
@@ -202,7 +204,7 @@ class FileList {
 
     if (!file) {
       log.debug(`Changed file "${path}" ignored. Does not match any file in the list.`)
-      return Promise.resolve(this.files)
+      return this.files
     }
 
     const [stat] = await Promise.all([fs.statAsync(path), this._refreshing])

lib/helper.js

@@ -4,7 +4,6 @@ const fs = require('graceful-fs')
 const path = require('path')
 const _ = require('lodash')
 const useragent = require('useragent')
-const Promise = require('bluebird')
 const mm = require('minimatch')
 
 exports.browserFullNameToShort = (fullName) => {

lib/launcher.js

@@ -1,6 +1,5 @@
 'use strict'
 
-const Promise = require('bluebird')
 const Jobs = require('qjobs')
 
 const log = require('./logger').create('launcher')

lib/launchers/base.js

@@ -1,6 +1,5 @@
 const KarmaEventEmitter = require('../events').EventEmitter
 const EventEmitter = require('events').EventEmitter
-const Promise = require('bluebird')
 
 const log = require('../logger').create('launcher')
 const helper = require('../helper')

lib/server.js

@@ -3,7 +3,6 @@
 const SocketIO = require('socket.io')
 const di = require('di')
 const util = require('util')
-const Promise = require('bluebird')
 const spawn = require('child_process').spawn
 const tmp = require('tmp')
 const fs = require('fs')

lib/utils/bundle-utils.js

@@ -1,7 +1,6 @@
 'use strict'
 const PathUtils = require('./path-utils')
 const fs = require('fs')
-const Promise = require('bluebird')
 
 const BundleUtils = {
   bundleResource (inPath, outPath) {

lib/utils/net-utils.js

@@ -1,6 +1,5 @@
 'use strict'
 
-const Promise = require('bluebird')
 const net = require('net')
 
 const NetUtils = {

package.json

@@ -390,7 +390,6 @@
     "Karl Lindmark <[email protected]>"
   ],
   "dependencies": {
-    "bluebird": "^3.3.0",
     "body-parser": "^1.16.1",
     "braces": "^3.0.2",
     "chokidar": "^3.0.0",

test/.eslintrc

@@ -4,8 +4,7 @@
   },
   "globals": {
     "expect": true,
-    "sinon": true,
-    "scheduleNextTick": true
+    "sinon": true
   },
   "rules": {
     "no-unused-expressions": "off"

test/unit/file-list.spec.js

@@ -1,6 +1,5 @@
 'use strict'
 
-const Promise = require('bluebird')
 const EventEmitter = require('events').EventEmitter
 const mocks = require('mocks')
 const proxyquire = require('proxyquire')
@@ -448,16 +447,14 @@ describe('FileList', () => {
         helper: helper,
         glob: glob,
         'graceful-fs': mockFs,
-        path: pathLib.posix,
-        bluebird: Promise
+        path: pathLib.posix
       })
 
       list = new List(patterns('/some/*.js', '*.txt'), ['/secret/*.txt'], emitter, preprocess, 100)
     })
 
     afterEach(() => {
       clock.restore()
-      Promise.setScheduler((fn) => process.nextTick(fn))
     })
 
     it('does not add excluded files', () => {
@@ -514,14 +511,14 @@ describe('FileList', () => {
 
       return list.refresh().then(() => {
         preprocess.resetHistory()
-        sinon.spy(mockFs, 'stat')
+        sinon.spy(mockFs, 'statAsync')
 
         return Promise.all([
           list.addFile('/some/d.js'),
           list.addFile('/some/d.js')
         ]).then(() => {
           expect(preprocess).to.have.been.calledOnce
-          expect(mockFs.stat).to.have.been.calledOnce
+          expect(mockFs.statAsync).to.have.been.calledOnce
         })
       })
     })
@@ -555,7 +552,6 @@ describe('FileList', () => {
     beforeEach(() => {
       patternList = PATTERN_LIST
       mg = MG
-      Promise.setScheduler((fn) => fn())
 
       emitter = new EventEmitter()
 
@@ -576,8 +572,7 @@ describe('FileList', () => {
         helper: helper,
         glob: glob,
         'graceful-fs': mockFs,
-        path: pathLib.posix,
-        bluebird: Promise
+        path: pathLib.posix
       })
 
       mockFs._touchFile('/some/a.js', '2012-04-04')
@@ -586,7 +581,6 @@ describe('FileList', () => {
 
     afterEach(() => {
       clock.restore()
-      Promise.setScheduler((fn) => process.nextTick(fn))
     })
 
     it('updates mtime and fires "file_list_modified"', () => {
@@ -680,7 +674,6 @@ describe('FileList', () => {
     beforeEach(() => {
       patternList = PATTERN_LIST
       mg = MG
-      Promise.setScheduler((fn) => fn())
 
       emitter = new EventEmitter()
 
@@ -701,8 +694,7 @@ describe('FileList', () => {
         helper: helper,
         glob: glob,
         'graceful-fs': mockFs,
-        path: pathLib.posix,
-        bluebird: Promise
+        path: pathLib.posix
       })
 
       modified = sinon.stub()
@@ -711,7 +703,6 @@ describe('FileList', () => {
 
     afterEach(() => {
       clock.restore()
-      Promise.setScheduler((fn) => process.nextTick(fn))
     })
 
     it('removes the file from the list and fires "file_list_modified"', () => {
@@ -762,7 +753,6 @@ describe('FileList', () => {
     beforeEach(() => {
       patternList = PATTERN_LIST
       mg = MG
-      Promise.setScheduler((fn) => { fn() })
 
       emitter = new EventEmitter()
 
@@ -786,14 +776,12 @@ describe('FileList', () => {
         helper: helper,
         glob: glob,
         'graceful-fs': mockFs,
-        path: pathLib.posix,
-        bluebird: Promise
+        path: pathLib.posix
       })
     })
 
     afterEach(() => {
       clock.restore()
-      Promise.setScheduler((fn) => process.nextTick(fn))
     })
 
     it('debounces calls to emitModified', () => {

test/unit/launcher.spec.js

@@ -1,6 +1,5 @@
 'use strict'
 
-const Promise = require('bluebird')
 const di = require('di')
 
 const events = require('../../lib/events')
@@ -65,14 +64,6 @@ describe('launcher', () => {
   let lastGeneratedId = null
   launcher.Launcher.generateId = () => ++lastGeneratedId
 
-  before(() => {
-    Promise.setScheduler((fn) => fn())
-  })
-
-  after(() => {
-    Promise.setScheduler((fn) => process.nextTick(fn))
-  })
-
   beforeEach(() => {
     lastGeneratedId = 0
     FakeBrowser._instances = []
@@ -252,7 +243,7 @@ describe('launcher', () => {
         expect(browser.forceKill).to.have.been.called
       })
 
-      it('should call callback when all processes killed', () => {
+      it('should call callback when all processes killed', (done) => {
         const exitSpy = sinon.spy()
 
         l.launch(['Fake', 'Fake'], 1)
@@ -264,18 +255,17 @@ describe('launcher', () => {
         let browser = FakeBrowser._instances.pop()
         browser.forceKill.resolve()
 
-        scheduleNextTick(() => {
+        setImmediate(() => {
           expect(exitSpy).not.to.have.been.called
-        })
 
-        scheduleNextTick(() => {
           // finish the second browser
           browser = FakeBrowser._instances.pop()
           browser.forceKill.resolve()
-        })
 
-        scheduleNextTick(() => {
-          expect(exitSpy).to.have.been.called
+          setImmediate(() => {
+            expect(exitSpy).to.have.been.called
+            done()
+          })
         })
       })