fix: compiling `coffee.coffee` produces `.js` file.

lib/coffee-script/helpers.js

@@ -152,7 +152,7 @@
     }
     parts = file.split('.');
     parts.pop();
-    if (parts[parts.length - 1] === 'coffee') {
+    if (parts[parts.length - 1] === 'coffee' && parts.length > 1) {
       parts.pop();
     }
     return parts.join('.');

src/helpers.coffee

@@ -110,7 +110,7 @@ exports.baseFileName = (file, stripExt = no) ->
   return file unless stripExt
   parts = file.split('.')
   parts.pop()
-  parts.pop() if parts[parts.length - 1] is 'coffee'
+  parts.pop() if parts[parts.length - 1] is 'coffee' and parts.length > 1
   parts.join('.')
 
 # Determine if a filename represents a CoffeeScript file.

test/helpers.coffee

@@ -2,7 +2,7 @@
 # -------
 
 # pull the helpers from `CoffeeScript.helpers` into local variables
-{starts, ends, compact, count, merge, extend, flatten, del, last} = CoffeeScript.helpers
+{starts, ends, compact, count, merge, extend, flatten, del, last, baseFileName} = CoffeeScript.helpers
 
 
 # `starts`
@@ -94,3 +94,25 @@ test "the `last` helper returns the last item of an array-like object", ->
 test "the `last` helper allows one to specify an optional offset", ->
   ary = [0, 1, 2, 3, 4]
   eq 2, last(ary, 2)
+
+
+# `baseFileName`
+
+test "the `baseFileName` helper returns the file name to write to", ->
+  ext = '.js'
+  sourceToCompiled =
+    'a.coffee': 'a' + ext
+    'b.coffee': 'b' + ext
+    'a.litcoffee': 'a' + ext
+    'b.litcoffee': 'b' + ext
+    'a.lit': 'a' + ext
+    'b.lit': 'b' + ext
+    'a.coffee.md': 'a' + ext
+    'b.coffee.md': 'b' + ext
+    'coffee.coffee': 'coffee' + ext
+
+  for sourceFileName, expectedFileName of sourceToCompiled
+    name = baseFileName sourceFileName, yes
+    filename = name + ext
+    eq filename, expectedFileName
+