Search current directory if no paths are specified

This fixes a regression in behaviour from 2.x to 3.

Closes #150

src/flake8/checker.py

@@ -253,6 +253,10 @@ class Manager(object):
         """Create checkers for each file."""
         if paths is None:
             paths = self.arguments
+
+        if not paths:
+            paths = ['.']
+
         filename_patterns = self.options.filename
 
         # NOTE(sigmavirus24): Yes this is a little unsightly, but it's our
@@ -273,6 +277,7 @@ class Manager(object):
                                                  self.is_path_excluded)
             if should_create_file_checker(filename)
         ]
+        LOG.info('Checking %d files', len(self.checkers))
 
     def report(self):
         # type: () -> (int, int)
@@ -340,6 +345,9 @@ class Manager(object):
                 raise
             LOG.warning('Running in serial after OS exception, %r', oserr)
             self.run_serial()
+        except KeyboardInterrupt:
+            LOG.warning('Flake8 was interrupted by the user')
+            raise exceptions.EarlyQuit('Early quit while running checks')
 
     def start(self, paths=None):
         """Start checking files.

src/flake8/exceptions.py

@@ -7,6 +7,12 @@ class Flake8Exception(Exception):
     pass
 
 
+class EarlyQuit(Flake8Exception):
+    """Except raised when encountering a KeyboardInterrupt."""
+
+    pass
+
+
 class FailedToLoadPlugin(Flake8Exception):
     """Exception raised when a plugin fails to load."""
 

src/flake8/utils.py

@@ -209,16 +209,22 @@ def filenames_from(arg, predicate=None):
         predicate = _default_predicate
     if os.path.isdir(arg):
         for root, sub_directories, files in os.walk(arg):
-            for filename in files:
-                joined = os.path.join(root, filename)
-                if predicate(joined):
-                    continue
-                yield joined
+            if predicate(root):
+                sub_directories[:] = []
+                continue
+
             # NOTE(sigmavirus24): os.walk() will skip a directory if you
             # remove it from the list of sub-directories.
             for directory in sub_directories:
-                if predicate(directory):
+                joined = os.path.join(root, directory)
+                if predicate(directory) or predicate(joined):
                     sub_directories.remove(directory)
+
+            for filename in files:
+                joined = os.path.join(root, filename)
+                if predicate(joined) or predicate(filename):
+                    continue
+                yield joined
     else:
         yield arg
 

tox.ini

@@ -132,7 +132,7 @@ ignore = D203
 # NOTE(sigmavirus24): Once we release 3.0.0 this exclude option can be specified
 # across multiple lines. Presently it cannot be specified across multiple lines.
 # :-(
-exclude = .git,__pycache__,docs/source/conf.py,old,build,dist,tests/fixtures/
+exclude = .tox,.git,__pycache__,docs/source/conf.py,build,dist,tests/fixtures/*,*.pyc
 max-complexity = 10
 import-order-style = google
 application-import-names = flake8