Prevent multi-modifier keystrokes from being enqueued

Signed-off-by: Nathan Sobo <nathan@github.com>

Author: maxbrunsfeld

spec/keymap-manager-spec.coffee

@@ -294,7 +294,7 @@ describe "KeymapManager", ->
 
     it "does not enqueue keydown events consisting only of modifier keys", ->
       element = $$ -> @div class: 'a'
-      keymapManager.addKeymap 'test', '.a': 'ctrl-a ctrl-b': 'command'
+      keymapManager.addKeymap 'test', '.a': 'ctrl-a ctrl-alt-b': 'command'
       events = []
       element.addEventListener 'command', -> events.push('command')
 
@@ -303,7 +303,8 @@ describe "KeymapManager", ->
       keymapManager.handleKeyboardEvent(keydownEvent('ctrl', target: element))
       keymapManager.handleKeyboardEvent(keydownEvent('a', ctrl: true, target: element))
       keymapManager.handleKeyboardEvent(keydownEvent('ctrl', target: element))
-      keymapManager.handleKeyboardEvent(keydownEvent('b', ctrl: true, target: element))
+      keymapManager.handleKeyboardEvent(keydownEvent('alt', ctrl: true, target: element))
+      keymapManager.handleKeyboardEvent(keydownEvent('b', ctrl: true, alt: true, target: element))
 
       expect(events).toEqual ['command']
 

src/helpers.coffee

@@ -4,6 +4,8 @@
 AtomModifiers = new Set
 AtomModifiers.add(modifier) for modifier in ['ctrl', 'alt', 'shift', 'cmd']
 
+AtomModifierRegex = /(ctrl|alt|shift|cmd)$/
+
 KeyboardEventModifiers = new Set
 KeyboardEventModifiers.add(modifier) for modifier in ['Control', 'Alt', 'Shift', 'Meta']
 
@@ -147,8 +149,8 @@ exports.keystrokeForKeyboardEvent = (event, dvorakQwertyWorkaroundEnabled) ->
 exports.calculateSpecificity = (selector) ->
   SpecificityCache[selector] ?= specificity(selector)
 
-exports.isAtomModifier = (key) ->
-  AtomModifiers.has(key)
+exports.isAtomModifier = (keystroke) ->
+  AtomModifiers.has(keystroke) or AtomModifierRegex.test(keystroke)
 
 exports.keydownEvent = (key, {ctrl, shift, alt, cmd, keyCode, target, location}={}) ->
   event = document.createEvent('KeyboardEvent')