Allow to use pathlib.Path as implicit converter (#47)

* Allow to use pathlib.Path as implicit converter
* Check for subclass of implicit converters
* Deal with Python 2 compatibility for pathlib

clize/parser.py

@@ -16,6 +16,14 @@
 
 from clize import errors, util
 
+try:
+    import pathlib
+except ImportError:
+    try:
+        import pathlib2 as pathlib
+    except ImportError:
+        pathlib = None
+
 
 class ParameterFlag(object):
     def __init__(self, name, prefix='clize.Parameter'):
@@ -232,15 +240,26 @@ def is_true(arg):
     six.binary_type: identity,
 }
 
+if pathlib:
+    @value_converter(name='PATH')
+    def path_converter(arg):
+        return pathlib.Path(arg)
+
+    _implicit_converters[pathlib.PurePath] = path_converter
+
 
 def get_value_converter(annotation):
     try:
         return _implicit_converters[annotation]
     except KeyError:
         pass
-    if not getattr(annotation, '_clize__value_converter', False):
-        raise ValueError('{0!r} is not a value converter'.format(annotation))
-    return annotation
+    if getattr(annotation, '_clize__value_converter', False):
+        return annotation
+    if isinstance(annotation, type):
+        for ic in _implicit_converters:
+            if issubclass(annotation, ic):
+                return _implicit_converters[ic]
+    raise ValueError('{0!r} is not a value converter'.format(annotation))
 
 
 class ParameterWithValue(Parameter):

clize/tests/test_parser.py

@@ -7,13 +7,22 @@
 from clize import parser, errors, util
 from clize.tests.util import Fixtures
 
+try:
+    import pathlib
+    pathlib_name = "pathlib"
+except ImportError:
+    import pathlib2 as pathlib
+    pathlib_name = "pathlib2 as pathlib"
+
 
 _ic = parser._implicit_converters
 
 
 class FromSigTests(Fixtures):
     def _test(self, sig_str, typ, str_rep, attrs):
-        sig = support.s(sig_str, pre='from clize import Parameter')
+        pre_code = ("import {}; from clize import"
+                    " Parameter".format(pathlib_name))
+        sig = support.s(sig_str, pre=pre_code)
         return self._do_test(sig, typ, str_rep, attrs)
 
     def _do_test(self, sig, typ, str_rep, attrs):
@@ -44,6 +53,12 @@ def _do_test(self, sig, typ, str_rep, attrs):
         'conv': _ic[int], 'default': 3, 'required': False,
         'argument_name': 'one', 'display_name': 'one',
         'undocumented': False, 'last_option': None}
+    pos_default_path = (
+        'file=pathlib.Path(\'/tmp\')', parser.PositionalParameter, '[file]', {
+            'conv': _ic[pathlib.PurePath],
+            'default': pathlib.Path('/tmp'), 'argument_name': 'file',
+            'required': False, 'undocumented': False,
+            'last_option': None, 'display_name': 'file'})
     pos_default_but_required = (
         'one:Parameter.REQUIRED=3', parser.PositionalParameter, 'one', {
             'conv': _ic[int], 'default': util.UNSET, 'required': True,

tox.ini

@@ -13,6 +13,7 @@ usedevelop=True
 deps=
     unittest2
     repeated_test
+    pathlib2
     python-dateutil
     Pygments
     docs: sphinx