changeset:   71898:148c84b766e8
branch:      2.7
tag:         tip
parent:      71890:b4ccf8e1fdba
user:        Arnaud Fontaine <arnau@debian.org>
date:        Thu Aug 18 17:12:32 2011 +0900
summary:     #12776: call argparse type function (specified by add_argument) only once.

diff -r b4ccf8e1fdba -r 148c84b766e8 Lib/argparse.py
--- a/Lib/argparse.py	Tue Aug 16 22:26:48 2011 -0500
+++ b/Lib/argparse.py	Thu Aug 18 17:12:32 2011 +0900
@@ -1705,10 +1705,7 @@
             if action.dest is not SUPPRESS:
                 if not hasattr(namespace, action.dest):
                     if action.default is not SUPPRESS:
-                        default = action.default
-                        if isinstance(action.default, basestring):
-                            default = self._get_value(action, default)
-                        setattr(namespace, action.dest, default)
+                        setattr(namespace, action.dest, action.default)
 
         # add any parser defaults that aren't present
         for dest in self._defaults:
@@ -1936,12 +1933,23 @@
         if positionals:
             self.error(_('too few arguments'))
 
-        # make sure all required actions were present
+        # make sure all required actions were present and also convert
+        # action defaults which were not given as arguments
         for action in self._actions:
-            if action.required:
-                if action not in seen_actions:
+            if action not in seen_actions:
+                if action.required:
                     name = _get_action_name(action)
                     self.error(_('argument %s is required') % name)
+                else:
+                    # Convert action default now instead of doing it before
+                    # parsing arguments to avoid calling convert functions
+                    # twice (which may fail) if the argument was given, but
+                    # only if it was defined already in the namespace
+                    if hasattr(namespace, action.dest) and \
+                       isinstance(action.default, basestring) and \
+                       action.default == getattr(namespace, action.dest):
+                        setattr(namespace, action.dest,
+                                self._get_value(action, action.default))
 
         # make sure all required groups had one option present
         for group in self._mutually_exclusive_groups:
diff -r b4ccf8e1fdba -r 148c84b766e8 Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py	Tue Aug 16 22:26:48 2011 -0500
+++ b/Lib/test/test_argparse.py	Thu Aug 18 17:12:32 2011 +0900
@@ -4414,6 +4414,22 @@
         else:
             self.fail()
 
+# ================================================
+# Check that the type function is called only once
+# ================================================
+
+class TestTypeFunctionCallOnlyOnce(TestCase):
+
+    def test_type_function_call_only_once(self):
+        def spam(string_to_convert):
+            self.assertEqual(string_to_convert, 'spam!')
+            return 'foo_converted'
+
+        parser = argparse.ArgumentParser()
+        parser.add_argument('--foo', type=spam, default='bar')
+        args = parser.parse_args(['--foo', 'spam!'])
+        self.assertEqual(NS(foo='foo_converted'), args)
+
 # ======================
 # parse_known_args tests
 # ======================