Simplify prefix a bit

pre_commit/languages/script.py

@@ -12,5 +12,5 @@ install_environment = helpers.no_install
 
 def run_hook(prefix, hook, file_args):
     cmd = helpers.to_cmd(hook)
-    cmd = (prefix.prefix_dir + cmd[0],) + cmd[1:]
+    cmd = (prefix.path(cmd[0]),) + cmd[1:]
     return xargs(cmd, file_args)

pre_commit/prefix.py

@@ -5,16 +5,14 @@ import os.path
 
 class Prefix(object):
     def __init__(self, prefix_dir):
-        self.prefix_dir = prefix_dir.rstrip(os.sep) + os.sep
+        self.prefix_dir = prefix_dir
 
     def path(self, *parts):
-        path = os.path.join(self.prefix_dir, *parts)
-        return os.path.normpath(path)
+        return os.path.normpath(os.path.join(self.prefix_dir, *parts))
 
     def exists(self, *parts):
         return os.path.exists(self.path(*parts))
 
     def star(self, end):
-        return tuple(
-            path for path in os.listdir(self.prefix_dir) if path.endswith(end)
-        )
+        paths = os.listdir(self.prefix_dir)
+        return tuple(path for path in paths if path.endswith(end))

tests/prefix_test.py

@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-import os
+import os.path
 
 import pytest
 
@@ -12,30 +12,16 @@ def norm_slash(*args):
 
 
 @pytest.mark.parametrize(
-    ('input', 'expected_prefix'), (
-        norm_slash('.', './'),
-        norm_slash('foo', 'foo/'),
-        norm_slash('bar/', 'bar/'),
-        norm_slash('foo/bar', 'foo/bar/'),
-        norm_slash('foo/bar/', 'foo/bar/'),
+    ('prefix', 'path_end', 'expected_output'),
+    (
+        norm_slash('foo', '', 'foo'),
+        norm_slash('foo', 'bar', 'foo/bar'),
+        norm_slash('foo/bar', '../baz', 'foo/baz'),
+        norm_slash('./', 'bar', 'bar'),
+        norm_slash('./', '', '.'),
+        norm_slash('/tmp/foo', '/tmp/bar', '/tmp/bar'),
     ),
 )
-def test_init_normalizes_path_endings(input, expected_prefix):
-    instance = Prefix(input)
-    assert instance.prefix_dir == expected_prefix
-
-
-PATH_TESTS = (
-    norm_slash('foo', '', 'foo'),
-    norm_slash('foo', 'bar', 'foo/bar'),
-    norm_slash('foo/bar', '../baz', 'foo/baz'),
-    norm_slash('./', 'bar', 'bar'),
-    norm_slash('./', '', '.'),
-    norm_slash('/tmp/foo', '/tmp/bar', '/tmp/bar'),
-)
-
-
-@pytest.mark.parametrize(('prefix', 'path_end', 'expected_output'), PATH_TESTS)
 def test_path(prefix, path_end, expected_output):
     instance = Prefix(prefix)
     ret = instance.path(path_end)
@@ -48,10 +34,7 @@ def test_path_multiple_args():
     assert ret == os.path.join('foo', 'bar', 'baz')
 
 
-def test_exists_does_not_exist(tmpdir):
+def test_exists(tmpdir):
     assert not Prefix(str(tmpdir)).exists('foo')
-
-
-def test_exists_does_exist(tmpdir):
     tmpdir.ensure('foo')
     assert Prefix(str(tmpdir)).exists('foo')