Make sure showing errors works correctly

spec/command-installer-spec.coffee

@@ -20,10 +20,32 @@ describe "CommandInstaller on #darwin", ->
     spyOn(CommandInstaller::, 'getResourcesDirectory').andReturn(resourcesPath)
     spyOn(CommandInstaller::, 'getInstallDirectory').andReturn(installationPath)
 
+  it "shows an error dialog when installing commands interactively fails", ->
+    appDelegate = jasmine.createSpyObj("appDelegate", ["confirm"])
+    installer = new CommandInstaller("2.0.2", appDelegate)
+    spyOn(installer, "installAtomCommand").andCallFake (__, callback) -> callback(new Error("an error"))
+
+    installer.installShellCommandsInteractively()
+
+    expect(appDelegate.confirm).toHaveBeenCalledWith({
+      message: "Failed to install shell commands"
+      detailedMessage: "an error"
+    })
+
+    appDelegate.confirm.reset()
+    installer.installAtomCommand.andCallFake (__, callback) -> callback()
+    spyOn(installer, "installApmCommand").andCallFake (__, callback) -> callback(new Error("another error"))
+
+    installer.installShellCommandsInteractively()
+
+    expect(appDelegate.confirm).toHaveBeenCalledWith({
+      message: "Failed to install shell commands"
+      detailedMessage: "another error"
+    })
+
   describe "when using a stable version of atom", ->
     beforeEach ->
-      confirm = ->
-      installer = new CommandInstaller("2.0.2", confirm)
+      installer = new CommandInstaller("2.0.2")
 
     it "symlinks the atom command as 'atom'", ->
       installedAtomPath = path.join(installationPath, 'atom')

src/command-installer.coffee

@@ -35,7 +35,7 @@ class CommandInstaller
     process.resourcesPath
 
   installShellCommandsInteractively: ->
-    showErrorDialog = (error) ->
+    showErrorDialog = (error) =>
       @applicationDelegate.confirm
         message: "Failed to install shell commands"
         detailedMessage: error.message