fix(spellcheck): add tests and merge in Linux changes

spec/spellchecker-spec.coffee

@@ -40,6 +40,34 @@ describe "NylasSpellchecker", ->
     spyOn(@spellchecker, "getAvailableDictionaries").andReturn @fullDictList
     expect(@spellchecker.isLanguageAvailable("en")).toBe true
 
+  it "sets the correct default dictionary", ->
+    nodeSpellchecker = require('spellchecker')
+    spyOn(nodeSpellchecker, "setDictionary")
+    @spellchecker.setDictionary("en_US")
+    expect(nodeSpellchecker.setDictionary).toHaveBeenCalled()
+    expect(nodeSpellchecker.setDictionary.calls[0].args[0]).toBe "en_US"
+    dict = nodeSpellchecker.setDictionary.calls[0].args[1]
+    if process.platform is "darwin"
+      expect(dict.length).toBe 0
+    else if process.platform is "win32"
+      expect(dict.length).toBe 0
+    else if process.platform is "linux"
+      expect(dict.length).toBeGreaterThan 0
+
+  it "uses the passed-in dictionary", ->
+    nodeSpellchecker = require('spellchecker')
+    spyOn(nodeSpellchecker, "setDictionary")
+    @spellchecker.setDictionary("fr", "/path/to/dict")
+    expect(nodeSpellchecker.setDictionary).toHaveBeenCalled()
+    expect(nodeSpellchecker.setDictionary.calls[0].args[0]).toBe "fr"
+    dict = nodeSpellchecker.setDictionary.calls[0].args[1]
+    if process.platform is "darwin"
+      expect(dict).toBe "/path/to/dict"
+    else if process.platform is "win32"
+      expect(dict).toBe "/path/to/dict"
+    else if process.platform is "linux"
+      expect(dict).toBe "/path/to/dict"
+
   describe "when we don't recognize the language", ->
     beforeEach ->
       spyOn(@spellchecker, "getAvailableDictionaries").andReturn ["foo"]
@@ -87,12 +115,11 @@ describe "NylasSpellchecker", ->
 
     it "provides options for misspelled words", ->
       expect(@spellchecker.getCorrectionsForMisspelling("")).toEqual []
-      # TODO: Determine the reason OS X and/or Windows return an empty array
-      # for the string. -mbilker
+
       if process.platform is 'linux'
         expect(@spellchecker.getCorrectionsForMisspelling("asdfk")).toEqual ['asked', 'acidify', 'Assad']
-      else
-        expect(@spellchecker.getCorrectionsForMisspelling("asdfk")).toEqual []
+      else if process.platofrm is "darwin"
+        expect(@spellchecker.getCorrectionsForMisspelling("testt")).toEqual [ 'test', 'tests', 'testy', 'testa' ]
 
     it "still provides options for correctly spelled workds", ->
       expect(@spellchecker.getCorrectionsForMisspelling("hello").length).toBeGreaterThan 1

src/nylas-spellchecker.coffee

@@ -16,7 +16,7 @@ class NylasSpellchecker
 
   isSpelledCorrectly: (args...) => not @isMisspelled(args...)
 
-  setLanguage: (lang="", dict=@_getDictionaryPath()) ->
+  setLanguage: (lang="", dict="") ->
     @languageAvailable = @isLanguageAvailable(lang)
     if @languageAvailable
       spellCheck = @isSpelledCorrectly
@@ -28,15 +28,35 @@ class NylasSpellchecker
     if lang.length is 0 then lang = "en-US"
 
     @_setWebframeSpellchecker(lang, spellCheck)
+
+    if process.platform is "linux"
+      dictionaryPath = @_getHunspellDictionary()
+    else
+      # On Mac we defer to NSSpellChecker
+      # On Windows we use the Windows Spell Check API
+      #
+      # Both of those automatically provide a set of dictionaries based on
+      # the language string.
+      #
+      # On Windows 10 you can see the dictionaries that are available by
+      # looking in: C:\Users\YourName\AppData\Roaming\Microsoft\Spelling
+      #
+      # The `dictionaryPath` parameter is ignored on Mac & Windows by
+      # node-spellchecker
+      dictionaryPath = ""
+
+    if dict.length is 0 then dict = dictionaryPath
+
     spellchecker.setDictionary(lang, dict)
 
   # Separate method for testing
   _setWebframeSpellchecker: (lang, spellCheck) ->
     require('web-frame').setSpellCheckProvider(lang, false, {spellCheck})
 
-  # node-spellchecker's method for resolving the builtin hunspell dictionaries for Linux
-  # (From https://github.com/atom/node-spellchecker/blob/master/lib/spellchecker.js#L50-L61)
-  _getDictionaryPath: ->
+  # node-spellchecker's method for resolving the builtin hunspell
+  # dictionaries for Linux (From
+  # https://github.com/atom/node-spellchecker/blob/master/lib/spellchecker.js#L50-L61)
+  _getHunspellDictionary: ->
     dict = path.join(require.resolve('spellchecker'), '..', '..', 'vendor', 'hunspell_dictionaries')
     try
       # HACK: Special case being in an asar archive