[completion] Simplify and improve FileSystemAction.

It still has the issue where .. doesn't get completed with a trailing
slash.  bash does this but zsh doesn't.

Addresses issue #240.

core/completion.py

@@ -322,25 +322,32 @@ def __init__(self, dirs_only=False, exec_only=False, add_slash=False):
 
   def Matches(self, comp):
     to_complete = comp.to_complete
-    i = to_complete.rfind('/')
-    if i == -1:  # it looks like 'foo'
+
+    # Problem: .. and ../.. don't complete /.
+    # TODO: Set display_pos before fixing this.
+
+    #import os
+    #to_complete = os.path.normpath(to_complete)
+
+    dirname, basename = os_path.split(to_complete)
+    if dirname == '':  # We're completing in this directory
       to_list = '.'
-      base = ''
-    elif i == 0:  # it's an absolute path to_complete like / or /b
-      to_list = '/'
-      base = '/'
-    else:
-      to_list = to_complete[:i]
-      base = to_list
-      #log('to_list %r', to_list)
+    else:  # We're completing in some other directory
+      to_list = dirname
+
+    if 0:
+      log('basename %r', basename)
+      log('to_list %r', to_list)
+      log('dirname %r', dirname)
 
     try:
       names = posix.listdir(to_list)
     except OSError as e:
       return  # nothing
 
     for name in names:
-      path = os_path.join(base, name)
+      path = os_path.join(dirname, name)
+
       if path.startswith(to_complete):
         if self.dirs_only:  # add_slash not used here
           # NOTE: There is a duplicate isdir() check later to add a trailing

core/completion_test.py

@@ -127,14 +127,25 @@ def testExternalCommandAction(self):
     # executable files are accessed!
 
   def testFileSystemAction(self):
-    a = completion.FileSystemAction(add_slash=True)
+    CASES = [
+        # Dirs and files
+        ('c', ['core', 'configure']),
+        ('opy/doc', ['opy/doc']),
+    ]
+
+    a = completion.FileSystemAction()
+    for prefix, expected in CASES:
+      log('')
+      log('-- PREFIX %r', prefix)
+      comp = self._CompApi([], 0, prefix)
+      self.assertEqual(expected, list(a.Matches(comp)))
 
     os.system('mkdir -p /tmp/oil_comp_test')
     os.system('bash -c "touch /tmp/oil_comp_test/{one,two,three}"')
 
     # This test depends on actual file system content.  But we choose things
     # that shouldn't go away.
-    CASES = [
+    ADD_SLASH_CASES = [
         # Dirs and files
         ('c', ['core/', 'configure']),
         ('nonexistent/', []),
@@ -153,7 +164,8 @@ def testFileSystemAction(self):
         ('./b', ['./bin/', './benchmarks/', './build/']),
     ]
 
-    for prefix, expected in CASES:
+    a = completion.FileSystemAction(add_slash=True)
+    for prefix, expected in ADD_SLASH_CASES:
       log('')
       log('-- PREFIX %s', prefix)
       comp = self._CompApi([], 0, prefix)