Simplify grammar selection and its specs

spec/app/edit-session-spec.coffee

@@ -2048,13 +2048,13 @@ describe "EditSession", ->
   describe "when the 'grammars-loaded' event is triggered on the syntax global", ->
     it "reloads the edit session's grammar and re-tokenizes the buffer if it changes", ->
       editSession.destroy()
-      grammarToReturn = syntax.grammarByFileTypeSuffix('txt')
+      grammarToReturn = syntax.grammarByPath('a.txt')
       spyOn(syntax, 'selectGrammar').andCallFake -> grammarToReturn
 
       editSession = project.buildEditSession('sample.js', autoIndent: false)
       expect(editSession.lineForScreenRow(0).tokens.length).toBe 1
 
-      grammarToReturn = syntax.grammarByFileTypeSuffix('js')
+      grammarToReturn = syntax.grammarByPath('a.js')
       syntax.trigger 'grammars-loaded'
       expect(editSession.lineForScreenRow(0).tokens.length).toBeGreaterThan 1
 

spec/app/syntax-spec.coffee

@@ -2,11 +2,12 @@ fs = require 'fs-utils'
 
 describe "the `syntax` global", ->
   describe ".selectGrammar(filePath)", ->
-    it "uses the filePath's extension to load the correct grammar", ->
-      expect(syntax.selectGrammar("file.js").name).toBe "JavaScript"
-
-    it "uses the filePath's base name if there is no extension", ->
-      expect(syntax.selectGrammar("Rakefile").name).toBe "Ruby"
+    it "can use the filePath to load the correct grammar based on the grammar's filetype", ->
+      expect(syntax.selectGrammar("file.js").name).toBe "JavaScript" # based on extension (.js)
+      expect(syntax.selectGrammar("/tmp/.git/config").name).toBe "Git Config" # based on end of the path (.git/config)
+      expect(syntax.selectGrammar("Rakefile").name).toBe "Ruby" # based on the file's basename (Rakefile)
+      expect(syntax.selectGrammar("curb").name).toBe "Plain Text"
+      expect(syntax.selectGrammar("/hu.git/config").name).toBe "Plain Text"
 
     it "uses the filePath's shebang line if the grammar cannot be determined by the extension or basename", ->
       filePath = require.resolve("fixtures/shebang")
@@ -29,11 +30,6 @@ describe "the `syntax` global", ->
       expect(syntax.selectGrammar(filePath, filePathContents).name).toBe "Ruby"
       expect(fs.read).not.toHaveBeenCalled()
 
-    it "uses the grammar's fileType as a suffix of the full filePath if the grammar cannot be determined by shebang line", ->
-      expect(syntax.selectGrammar("/tmp/.git/config").name).toBe "Git Config"
-
-    it "uses plain text if no grammar can be found", ->
-      expect(syntax.selectGrammar("this-is-not-a-real-file").name).toBe "Plain Text"
 
   describe ".getProperty(scopeDescriptor)", ->
     it "returns the property with the most specific scope selector", ->

src/app/syntax.coffee

@@ -5,6 +5,8 @@ Specificity = require 'specificity'
 fs = require 'fs-utils'
 EventEmitter = require 'event-emitter'
 NullGrammar = require 'null-grammar'
+nodePath = require 'path'
+pathSplitRegex = new RegExp("[#{nodePath.sep}.]")
 
 module.exports =
 class Syntax
@@ -25,19 +27,17 @@ class Syntax
 
   selectGrammar: (filePath, fileContents) ->
     return @grammarsByFileType["txt"] ? @nullGrammar unless filePath
+    @grammarByFirstLineRegex(filePath, fileContents) ?
+      @grammarByPath(filePath) ?
+      @grammarsByFileType["txt"] ?
+      @nullGrammar
 
-    extension = fs.extension(filePath)?[1..]
-    if filePath and extension.length == 0
-      extension = fs.base(filePath)
-
-    @grammarByFirstLineRegex(filePath, fileContents) or
-      @grammarsByFileType[extension] or
-      @grammarByFileTypeSuffix(filePath) or
-      @grammarsByFileType["txt"] ? @nullGrammar
-
-  grammarByFileTypeSuffix: (filePath) ->
+  grammarByPath: (path) ->
+    pathComponents = path.split(pathSplitRegex)
     for fileType, grammar of @grammarsByFileType
-      return grammar if _.endsWith(filePath, fileType)
+      fileTypeComponents = fileType.split(pathSplitRegex)
+      pathSuffix = pathComponents[-fileTypeComponents.length..-1]
+      return grammar if _.isEqual(pathSuffix, fileTypeComponents)
 
   grammarByFirstLineRegex: (filePath, fileContents) ->
     try