Fall back to system root for cmd.exe path

spec/buffered-process-spec.coffee

@@ -1,5 +1,6 @@
-BufferedProcess  = require '../src/buffered-process'
 ChildProcess = require 'child_process'
+path = require 'path'
+BufferedProcess  = require '../src/buffered-process'
 
 describe "BufferedProcess", ->
   describe "when a bad command is specified", ->
@@ -42,7 +43,7 @@ describe "BufferedProcess", ->
           expect(window.onerror.mostRecentCall.args[0]).toContain 'Failed to spawn command `bad-command-nope`'
           expect(window.onerror.mostRecentCall.args[4].name).toBe 'BufferedProcessError'
 
-  describe "when the explorer command is spawned on Windows", ->
+  describe "on Windows", ->
     originalPlatform = null
 
     beforeEach ->
@@ -61,6 +62,14 @@ describe "BufferedProcess", ->
     afterEach ->
       Object.defineProperty process, 'platform', value: originalPlatform
 
-    it "doesn't quote arguments of the form /root,C...", ->
+    describe "when the explorer command is spawned on Windows", ->
-      new BufferedProcess({command: 'explorer.exe', args: ['/root,C:\\foo']})
+      it "doesn't quote arguments of the form /root,C...", ->
-      expect(ChildProcess.spawn.argsForCall[0][1][2]).toBe '"explorer.exe /root,C:\\foo"'
+        new BufferedProcess({command: 'explorer.exe', args: ['/root,C:\\foo']})
+        expect(ChildProcess.spawn.argsForCall[0][1][2]).toBe '"explorer.exe /root,C:\\foo"'
+
+    it "spawns the command using a cmd.exe wrapper", ->
+      new BufferedProcess({command: 'dir'})
+      expect(path.basename(ChildProcess.spawn.argsForCall[0][0])).toBe 'cmd.exe'
+      expect(ChildProcess.spawn.argsForCall[0][1][0]).toBe '/s'
+      expect(ChildProcess.spawn.argsForCall[0][1][1]).toBe '/c'
+      expect(ChildProcess.spawn.argsForCall[0][1][2]).toBe '"dir"'

src/buffered-process.coffee

@@ -67,7 +67,7 @@ class BufferedProcess
       cmdArgs = ['/s', '/c', "\"#{cmdArgs.join(' ')}\""]
       cmdOptions = _.clone(options)
       cmdOptions.windowsVerbatimArguments = true
-      @process = ChildProcess.spawn(process.env.comspec or 'cmd.exe', cmdArgs, cmdOptions)
+      @process = ChildProcess.spawn(@getCmdPath(), cmdArgs, cmdOptions)
     else
       @process = ChildProcess.spawn(command, args, options)
     @killed = false
@@ -199,6 +199,14 @@ class BufferedProcess
     else
       false
 
+  getCmdPath: ->
+    if process.env.comspec
+      process.env.compec
+    else if process.env.SystemRoot
+      path.join(process.env.SystemRoot, 'System32', 'cmd.exe')
+    else
+      'cmd.exe'
+
   # Public: Terminate the process.
   kill: ->
     return if @killed