Upon inserting '(', insert matching ')' character after cursor

spec/app/language-mode-spec.coffee

@@ -8,6 +8,17 @@ describe "LanguageMode", ->
   afterEach ->
     editSession.destroy()
 
+  describe "common behavior", ->
+    beforeEach ->
+      editSession = fixturesProject.buildEditSessionForPath('sample.js', autoIndent: false)
+      { buffer, languageMode } = editSession
+
+    describe "matching character insertion", ->
+      describe "when ( is inserted", ->
+        it "inserts a matching ) following the cursor", ->
+          editSession.insertText '('
+          expect(buffer.lineForRow(0)).toMatch /^\(\)/
+
   describe "javascript", ->
     beforeEach ->
       editSession = fixturesProject.buildEditSessionForPath('sample.js', autoIndent: false)

src/app/language-mode.coffee

@@ -1,5 +1,6 @@
 AceAdaptor = require 'ace-adaptor'
 Range = require 'range'
+_ = require 'underscore'
 
 module.exports =
 class LanguageMode
@@ -8,6 +9,12 @@ class LanguageMode
     @aceMode = @requireAceMode()
     @aceAdaptor = new AceAdaptor(@editSession)
 
+    _.adviseBefore @editSession, 'insertText', (text) ->
+      if text == '('
+        @insertText '()'
+        @moveCursorLeft()
+        false
+
   requireAceMode: (fileExtension) ->
     modeName = switch @editSession.buffer.getExtension()
       when 'js' then 'javascript'