extract process spawning from squirrel-update

spec/spawner-spec.coffee

@@ -0,0 +1,57 @@
+ChildProcess = require 'child_process'
+Spawner = require '../src/browser/spawner'
+
+describe "Spawner", ->
+  beforeEach ->
+    # Prevent any commands from actually running and affecting the host
+    originalSpawn = ChildProcess.spawn
+
+    harmlessSpawn =
+      # Just spawn something that won't actually modify the host
+      if process.platform is 'win32'
+        originalSpawn('dir')
+      else
+        originalSpawn('ls')
+
+    spyOn(ChildProcess, 'spawn').andCallFake (command, args, callback) -> 
+      harmlessSpawn
+
+  it "invokes passed callback", ->
+    someCallback = jasmine.createSpy('someCallback')
+    
+    Spawner.spawn('some-command', 'some-args', someCallback)
+
+    waitsFor ->
+      someCallback.callCount is 1
+
+  it "spawns passed command with arguments", ->
+    actualCommand = null
+    actualArgs = null
+
+    # Redefine fake invocation, so to remember passed arguments
+    jasmine.unspy(ChildProcess, 'spawn')
+    spyOn(ChildProcess, 'spawn').andCallFake (command, args) ->
+      actualCommand = command
+      actualArgs = args
+      harmlessSpawn
+
+    expectedCommand = 'some-command'
+    expectedArgs = 'some-args'
+    someCallback = jasmine.createSpy('someCallback')
+
+    Spawner.spawn(expectedCommand, expectedArgs, someCallback)
+
+    expect(actualCommand).toBe expectedCommand
+    expect(actualArgs).toBe expectedArgs
+
+  it "ignores errors by spawned process", ->
+    # Redefine fake invocation, so to cause an error
+    jasmine.unspy(ChildProcess, 'spawn')
+    spyOn(ChildProcess, 'spawn').andCallFake -> throw new Error("EBUSY")
+
+    someCallback = jasmine.createSpy('someCallback')
+
+    expect(Spawner.spawn('some-command', 'some-args', someCallback)).toBe undefined
+
+    waitsFor ->
+      someCallback.callCount is 1

spec/squirrel-update-spec.coffee

@@ -1,39 +1,22 @@
-ChildProcess = require 'child_process'
 {EventEmitter} = require 'events'
 fs = require 'fs-plus'
 path = require 'path'
 temp = require 'temp'
 SquirrelUpdate = require '../src/browser/squirrel-update'
+Spawner = require '../src/browser/spawner'
 
 describe "Windows Squirrel Update", ->
   tempHomeDirectory = null
-  originalSpawn = ChildProcess.spawn
-  
-  harmlessSpawn = ->
-    # Just spawn something that won't actually modify the host
-    if process.platform is 'win32'
-      originalSpawn('dir')
-    else
-      originalSpawn('ls')
 
   beforeEach ->
     # Prevent the actual home directory from being manipulated
     tempHomeDirectory = temp.mkdirSync('atom-temp-home-')
     spyOn(fs, 'getHomeDirectory').andReturn(tempHomeDirectory)
 
-    # Prevent any commands from actually running and affecting the host
-    spyOn(ChildProcess, 'spawn').andCallFake (command, args) ->
-      harmlessSpawn()
-
-  it "ignores errors spawning Squirrel", ->
-    jasmine.unspy(ChildProcess, 'spawn')
-    spyOn(ChildProcess, 'spawn').andCallFake -> throw new Error("EBUSY")
-
-    app = quit: jasmine.createSpy('quit')
-    expect(SquirrelUpdate.handleStartupEvent(app, '--squirrel-install')).toBe true
-
-    waitsFor ->
-      app.quit.callCount is 1
+    # Prevent any spawned command from actually running and affecting the host
+    spyOn(Spawner, 'spawn').andCallFake (command, args, callback) -> 
+      # do nothing on command, just run passed callback
+      invokeCallback callback
 
   it "quits the app on all squirrel events", ->
     app = quit: jasmine.createSpy('quit')
@@ -69,51 +52,52 @@ describe "Windows Squirrel Update", ->
 
   describe "Desktop shortcut", ->
     desktopShortcutPath = '/non/existing/path'
-    
+
     beforeEach ->
       desktopShortcutPath = path.join(tempHomeDirectory, 'Desktop', 'Atom.lnk')
       
-      jasmine.unspy(ChildProcess, 'spawn')
-      spyOn(ChildProcess, 'spawn').andCallFake (command, args) ->
+      jasmine.unspy(Spawner, 'spawn')
+      spyOn(Spawner, 'spawn').andCallFake (command, args, callback) ->
         if path.basename(command) is 'Update.exe' and args?[0] is '--createShortcut'
-          fs.writeFileSync(path.join(tempHomeDirectory, 'Desktop', 'Atom.lnk'), '')
-          harmlessSpawn()
+          fs.writeFileSync(desktopShortcutPath, '')
         else
-          throw new Error("API not mocked")
-      
+          # simply ignore other commands
+          
+        invokeCallback callback
+
     it "does not exist before install", ->
       expect(fs.existsSync(desktopShortcutPath)).toBe false
-    
+
     describe "on install", ->
       beforeEach ->
         app = quit: jasmine.createSpy('quit')
         SquirrelUpdate.handleStartupEvent(app, '--squirrel-install')
         waitsFor ->
           app.quit.callCount is 1
-        
+
       it "creates desktop shortcut", ->
         expect(fs.existsSync(desktopShortcutPath)).toBe true
-      
+
       describe "when shortcut is deleted and then app is updated", ->
         beforeEach ->
           fs.removeSync(desktopShortcutPath)
           expect(fs.existsSync(desktopShortcutPath)).toBe false
-          
+
           app = quit: jasmine.createSpy('quit')
           SquirrelUpdate.handleStartupEvent(app, '--squirrel-updated')
           waitsFor ->
             app.quit.callCount is 1
-            
+
         it "does not recreate shortcut", ->
           expect(fs.existsSync(desktopShortcutPath)).toBe false
-      
+
       describe "when shortcut is kept and app is updated", ->
         beforeEach ->
           app = quit: jasmine.createSpy('quit')
           SquirrelUpdate.handleStartupEvent(app, '--squirrel-updated')
           waitsFor ->
             app.quit.callCount is 1
-            
+
         it "still has desktop shortcut", ->
           expect(fs.existsSync(desktopShortcutPath)).toBe true
 
@@ -125,7 +109,13 @@ describe "Windows Squirrel Update", ->
       SquirrelUpdate.restartAtom(app)
       expect(app.quit.callCount).toBe 1
 
-      expect(ChildProcess.spawn.callCount).toBe 0
+      expect(Spawner.spawn.callCount).toBe 0
       app.emit('will-quit')
-      expect(ChildProcess.spawn.callCount).toBe 1
-      expect(path.basename(ChildProcess.spawn.argsForCall[0][0])).toBe 'atom.cmd'
+      expect(Spawner.spawn.callCount).toBe 1
+      expect(path.basename(Spawner.spawn.argsForCall[0][0])).toBe 'atom.cmd'
+
+# Run passed callback as Spawner.spawn() would do
+invokeCallback = (callback) ->
+  error = null
+  stdout = ''
+  callback?(error, stdout)

src/browser/spawner.coffee

@@ -0,0 +1,36 @@
+ChildProcess = require 'child_process'
+
+# Spawn a command and invoke the callback when it completes with an error
+# and the output from standard out.
+#
+# * `command`    The underlying OS command {String} to execute.
+# * `args` (optional) The {Array} with arguments to be passed to command.
+# * `callback` (optional) The {Function} to call after the command has run. It will be invoked with arguments:
+#   * `error` (optional) An {Error} object returned by the command, `null` if no error was thrown.
+#     * `code` Error code returned by the command.
+#     * `stdout`  The {String} output text generated by the command.
+#   * `stdout`  The {String} output text generated by the command.
+#
+# Returns `undefined`.
+exports.spawn = (command, args, callback) ->
+  stdout = ''
+
+  try
+    spawnedProcess = ChildProcess.spawn(command, args)
+  catch error
+    # Spawn can throw an error
+    process.nextTick -> callback?(error, stdout)
+    return
+
+  spawnedProcess.stdout.on 'data', (data) -> stdout += data
+
+  error = null
+  spawnedProcess.on 'error', (processError) -> error ?= processError
+  spawnedProcess.on 'close', (code, signal) ->
+    error ?= new Error("Command failed: #{signal ? code}") if code isnt 0
+    error?.code ?= code
+    error?.stdout ?= stdout
+    callback?(error, stdout)
+  # This is necessary if using Powershell 2 on Windows 7 to get the events to raise
+  # http://stackoverflow.com/questions/9155289/calling-powershell-from-nodejs
+  spawnedProcess.stdin.end()

src/browser/squirrel-update.coffee

@@ -1,6 +1,6 @@
-ChildProcess = require 'child_process'
 fs = require 'fs-plus'
 path = require 'path'
+Spawner = require './spawner'
 
 appFolder = path.resolve(process.execPath, '..')
 rootAtomFolder = path.resolve(appFolder, '..')
@@ -25,35 +25,9 @@ backgroundKeyPath = 'HKCU\\Software\\Classes\\directory\\background\\shell\\Atom
 applicationsKeyPath = 'HKCU\\Software\\Classes\\Applications\\atom.exe'
 environmentKeyPath = 'HKCU\\Environment'
 
-# Spawn a command and invoke the callback when it completes with an error
-# and the output from standard out.
-spawn = (command, args, callback) ->
-  stdout = ''
-
-  try
-    spawnedProcess = ChildProcess.spawn(command, args)
-  catch error
-    # Spawn can throw an error
-    process.nextTick -> callback?(error, stdout)
-    return
-
-  spawnedProcess.stdout.on 'data', (data) -> stdout += data
-
-  error = null
-  spawnedProcess.on 'error', (processError) -> error ?= processError
-  spawnedProcess.on 'close', (code, signal) ->
-    error ?= new Error("Command failed: #{signal ? code}") if code isnt 0
-    error?.code ?= code
-    error?.stdout ?= stdout
-    callback?(error, stdout)
-  # This is necessary if using Powershell 2 on Windows 7 to get the events to raise
-  # http://stackoverflow.com/questions/9155289/calling-powershell-from-nodejs
-  spawnedProcess.stdin.end()
-
-
 # Spawn reg.exe and callback when it completes
 spawnReg = (args, callback) ->
-  spawn(regPath, args, callback)
+  Spawner.spawn(regPath, args, callback)
 
 # Spawn powershell.exe and callback when it completes
 spawnPowershell = (args, callback) ->
@@ -69,16 +43,16 @@ spawnPowershell = (args, callback) ->
   args.unshift('RemoteSigned')
   args.unshift('-ExecutionPolicy')
   args.unshift('-noprofile')
-  spawn(powershellPath, args, callback)
+  Spawner.spawn(powershellPath, args, callback)
 
 # Spawn setx.exe and callback when it completes
 spawnSetx = (args, callback) ->
-  spawn(setxPath, args, callback)
+  Spawner.spawn(setxPath, args, callback)
 
 # Spawn the Update.exe with the given arguments and invoke the callback when
 # the command completes.
 spawnUpdate = (args, callback) ->
-  spawn(updateDotExe, args, callback)
+  Spawner.spawn(updateDotExe, args, callback)
 
 # Install the Open with Atom explorer context menu items via the registry.
 installContextMenu = (callback) ->
@@ -220,7 +194,7 @@ exports.existsSync = ->
 exports.restartAtom = (app) ->
   if projectPath = global.atomApplication?.lastFocusedWindow?.projectPath
     args = [projectPath]
-  app.once 'will-quit', -> spawn(path.join(binFolder, 'atom.cmd'), args)
+  app.once 'will-quit', -> Spawner.spawn(path.join(binFolder, 'atom.cmd'), args)
   app.quit()
 
 # Handle squirrel events denoted by --squirrel-* command line arguments.