First attempt at adding internationalization to the cat error message detection.

Fix the tests for inside virtualenvs and add warning if localization appears impossible.

Remove the language warnings for en_US locales and make sure they appear for others.

tests/rules/test_cat_dir.py

@@ -1,15 +1,63 @@
+import gettext
+import os
+import warnings
+
 import pytest
+
 from thefuck.rules.cat_dir import match, get_new_command
 from thefuck.types import Command
 
+# patch this so the libc locale is available in the testing virtualenv
+gettext._default_localedir = '/usr/share/locale'
 
-@pytest.mark.parametrize('command', [
-    Command('cat foo', 'cat: foo: Is a directory\n'),
-    Command('cat /foo/bar/', 'cat: /foo/bar/: Is a directory\n'),
-    Command('cat cat/', 'cat: cat/: Is a directory\n'),
-])
-def test_match(command):
-    assert match(command)
+lang_vars = ['LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG']
+
+
+@pytest.fixture(params=['en_US.UTF-8', 'fr_FR.UTF-8', 'en_US.ISO8859-1', 'fr_FR.ISO8859-1'])
+def language(request):
+    return request.param
+
+
+@pytest.fixture(params=[''] + lang_vars)
+def environment(request, language):
+    orig_env = os.environ.copy()
+
+    # empty the locale environment variables
+    for lang_var in lang_vars:
+        os.environ.pop(lang_var, None)
+
+    if request.param:
+        os.environ[request.param] = language
+
+    yield
+
+    os.environ = orig_env
+
+
+@pytest.fixture
+def eisdir(environment):
+    eisdir = gettext.translation('libc', fallback=True).gettext('Is a directory')
+    return eisdir
+
+
+@pytest.fixture(params=['foo', '/foo/var', 'cat/'])
+def cat_command(request, eisdir):
+    return (
+        Command('cat %s' % request.param, 'cat: %s: %s\n' % (request.param, eisdir)),
+        'ls %s' % request.param
+    )
+
+
+def test_localization_possible(language):
+    if not language.startswith('en_US'):
+        try:
+            gettext.translation('libc', languages=[language])
+        except FileNotFoundError as e:
+            warnings.warn("No '%s' translation file found for language '%s'; the localization tests for `cat_dir` will be ineffective" % (e.filename, language))
+
+
+def test_match(cat_command):
+    assert match(cat_command[0])
 
 
 @pytest.mark.parametrize('command', [
@@ -20,10 +68,5 @@ def test_not_match(command):
     assert not match(command)
 
 
-@pytest.mark.parametrize('command, new_command', [
-    (Command('cat foo', 'cat: foo: Is a directory\n'), 'ls foo'),
-    (Command('cat /foo/bar/', 'cat: /foo/bar/: Is a directory\n'), 'ls /foo/bar/'),
-    (Command('cat cat', 'cat: cat: Is a directory\n'), 'ls cat'),
-])
-def test_get_new_command(command, new_command):
-    assert get_new_command(command) == new_command
+def test_get_new_command(cat_command):
+    assert get_new_command(cat_command[0]) == cat_command[1]

thefuck/rules/cat_dir.py

@@ -1,8 +1,12 @@
+import gettext
+
+
 def match(command):
+    eisdir = gettext.translation('libc', fallback=True).gettext('Is a directory')
     return (
         command.script.startswith('cat') and
         command.output.startswith('cat: ') and
-        command.output.rstrip().endswith(': Is a directory')
+        command.output.rstrip().endswith(': %s' % eisdir)
     )