Merge branch 'develop' into test-coverage-improvements

3 files changed, 37 insertions, 3 deletions

diff --git a/isort/main.py b/isort/main.py
index b95a2999..a584c226 100644
--- a/isort/main.py
+++ b/isort/main.py
@@ -284,11 +284,16 @@ def parse_args(argv=None):
                         help='Tells isort to ignore whitespace differences when --check-only is being used.')
     parser.add_argument('-y', '--apply', dest='apply', action='store_true',
                         help='Tells isort to apply changes recursively without asking')
+    parser.add_argument('--unsafe', dest='unsafe', action='store_true',
+                        help='Tells isort to look for files in standard library directories, etc. '
+                             'where it may not be safe to operate in')
     parser.add_argument('files', nargs='*', help='One or more Python source files that need their imports sorted.')
 
     arguments = {key: value for key, value in vars(parser.parse_args(argv)).items() if value}
     if 'dont_order_by_type' in arguments:
         arguments['order_by_type'] = False
+    if arguments.pop('unsafe', False):
+        arguments['safety_excludes'] = False
     return arguments
 
 
diff --git a/isort/settings.py b/isort/settings.py
index 79ae6c4c..cb047158 100644
--- a/isort/settings.py
+++ b/isort/settings.py
@@ -27,6 +27,7 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 import fnmatch
 import io
 import os
+import re
 import posixpath
 import sys
 import warnings
@@ -48,6 +49,10 @@ except ImportError:
 MAX_CONFIG_SEARCH_DEPTH = 25  # The number of parent directories isort will look for a config file within
 DEFAULT_SECTIONS = ('FUTURE', 'STDLIB', 'THIRDPARTY', 'FIRSTPARTY', 'LOCALFOLDER')
 
+safety_exclude_re = re.compile(
+    r"/(\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|_build|buck-out|build|dist|lib/python[0-9].[0-9]+)/"
+)
+
 WrapModes = ('GRID', 'VERTICAL', 'HANGING_INDENT', 'VERTICAL_HANGING_INDENT', 'VERTICAL_GRID', 'VERTICAL_GRID_GROUPED',
              'VERTICAL_GRID_GROUPED_NO_COMMA', 'NOQA')
 WrapModes = namedtuple('WrapModes', WrapModes)(*range(len(WrapModes)))
@@ -145,7 +150,9 @@ default = {'force_to_top': [],
            'show_diff': False,
            'ignore_whitespace': False,
            'no_lines_before': [],
-           'no_inline_sort': False}
+           'no_inline_sort': False,
+           'safety_excludes': True,
+           }
 
 
 @lru_cache()
@@ -292,8 +299,13 @@ def _get_config_data(file_path, sections):
 
 def should_skip(filename, config, path='/'):
     """Returns True if the file should be skipped based on the passed in settings."""
+    normalized_path = posixpath.join(path.replace('\\', '/'), filename)
+
+    if config['safety_excludes'] and safety_exclude_re.search(normalized_path):
+        return True
+
     for skip_path in config['skip']:
-        if posixpath.abspath(posixpath.join(path.replace('\\', '/'), filename)) == posixpath.abspath(skip_path.replace('\\', '/')):
+        if posixpath.abspath(normalized_path) == posixpath.abspath(skip_path.replace('\\', '/')):
             return True
 
     position = os.path.split(filename)
diff --git a/test_isort.py b/test_isort.py
index 302abfc9..c0ddff7f 100644
--- a/test_isort.py
+++ b/test_isort.py
@@ -25,11 +25,12 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 
 from tempfile import NamedTemporaryFile
 import io
+import os
 import sys
 
 import pytest
 
-from isort import finders
+from isort import finders, main, settings
 from isort.isort import SortImports
 from isort.utils import exists_case_sensitive
 from isort.main import is_python_file
@@ -2623,3 +2624,19 @@ def test_command_line(tmpdir, capfd, multiprocess):
     # it informs us about fixing the files:
     assert str(tmpdir.join("file1.py")) in out
     assert str(tmpdir.join("file2.py")) in out
+
+    
+@pytest.mark.parametrize('enabled', (False, True))
+def test_safety_excludes(tmpdir, enabled):
+    tmpdir.join("victim.py").write("# ...")
+    tmpdir.mkdir(".tox").join("verysafe.py").write("# ...")
+    tmpdir.mkdir("lib").mkdir("python3.7").join("importantsystemlibrary.py").write("# ...")
+    config = dict(settings.default.copy(), safety_excludes=enabled)
+    skipped = []
+    file_names = set(os.path.relpath(f, str(tmpdir)) for f in main.iter_source_code([str(tmpdir)], config, skipped))
+    if enabled:
+        assert file_names == {'victim.py'}
+        assert len(skipped) == 2
+    else:
+        assert file_names == {'.tox/verysafe.py', 'lib/python3.7/importantsystemlibrary.py', 'victim.py'}
+        assert not skipped