Start fleshing out flake8.utils

Add parse_comma_separated_list, normalize_path, and normalize_paths and
add logic in OptionManager.parse_args to use the right normalize_path*
function based on comma_separated_list value of the option.

flake8/options/manager.py

@@ -150,13 +150,22 @@ class OptionManager(object):
         """Simple proxy to calling the OptionParser's parse_args method."""
         options, xargs = self.parser.parse_args(args, values)
         for option in self.options:
-            dest = option.dest
-            if option.normalize_paths:
-                old_value = getattr(options, dest)
-                setattr(options, dest, utils.normalize_paths(old_value))
-            elif option.comma_separated_list:
-                old_value = getattr(options, dest)
-                setattr(options, dest,
-                        utils.parse_comma_separated_list(old_value))
+            _normalize_option(options, option)
 
         return options, xargs
+
+
+def _normalize_option(options, option):
+    dest = option.dest
+    if option.normalize_paths:
+        old_value = getattr(options, dest)
+        # Decide whether to parse a list of paths or a single path
+        normalize = utils.normalize_path
+        if option.comma_separated_list:
+            normalize = utils.normalize_paths
+        setattr(options, dest, normalize(old_value))
+
+    elif option.comma_separated_list:
+        old_value = getattr(options, dest)
+        setattr(options, dest,
+                utils.parse_comma_separated_list(old_value))

flake8/utils.py

@@ -0,0 +1,50 @@
+"""Utility methods for flake8."""
+import os
+
+
+def parse_comma_separated_list(value):
+    """Parse a comma-separated list.
+
+    :param value:
+        String or list of strings to be parsed and normalized.
+    :returns:
+        List of values with whitespace stripped.
+    :rtype:
+        list
+    """
+    if not value:
+        return []
+
+    if not isinstance(value, (list, tuple)):
+        value = value.split(',')
+
+    return [item.strip() for item in value]
+
+
+def normalize_paths(paths, parent=os.curdir):
+    """Parse a comma-separated list of paths.
+
+    :returns:
+        The normalized paths.
+    :rtype:
+        [str]
+    """
+    paths = []
+    for path in parse_comma_separated_list(paths):
+        if '/' in path:
+            path = os.path.abspath(os.path.join(parent, path))
+        paths.append(path.rstrip('/'))
+    return paths
+
+
+def normalize_path(path, parent=os.curdir):
+    """Normalize a single-path.
+
+    :returns:
+        The normalized path.
+    :rtype:
+        str
+    """
+    if '/' in path:
+        path = os.path.abspath(os.path.join(parent, path))
+    return path

tests/unit/test_utils.py

@@ -0,0 +1,14 @@
+"""Tests for flake8's utils module."""
+import pytest
+
+from flake8 import utils
+
+
+@pytest.mark.parametrize("value,expected", [
+    ("E123,\n\tW234,\n    E206", ["E123", "W234", "E206"]),
+    ("E123,W234,E206", ["E123", "W234", "E206"]),
+    (["E123", "W234", "E206"], ["E123", "W234", "E206"]),
+    (["E123", "\n\tW234", "\n    E206"], ["E123", "W234", "E206"]),
+])
+def test_parse_comma_separated_list(value, expected):
+    assert utils.parse_comma_separated_list(value) == expected