argparse.run now works with bound methods (instance methods and class methods).

2 files changed, 21 insertions, 0 deletions

diff --git a/argparse.py b/argparse.py
index 9ebf845..c1459fb 100644
--- a/argparse.py
+++ b/argparse.py
@@ -95,6 +95,7 @@ import re as _re
 import sys as _sys
 import textwrap as _textwrap
 import inspect as _inspect
+import types as _types
 
 from gettext import gettext as _
 
@@ -2414,6 +2415,14 @@ def _getfunctionspec(function):
     else:
         arg_names, varargs, varkw, defaults = _inspect.getargspec(function)
         kwonlyargs, kwonlydefaults, annotations = [], {}, {}
+
+    # A fix for class-methods and instance-methods is to remove the first
+    # argument name (which is self or cls).
+    # In case of (*args, **kwargs) we don't intervene.
+    if isinstance(function, _types.MethodType):
+        if len(arg_names) > 0:
+            arg_names.pop(0)
+
     return (arg_names, varargs, varkw, defaults,
             kwonlyargs, kwonlydefaults, annotations)
 
diff --git a/test/test_argparse.py b/test/test_argparse.py
index 462b065..8dc3c25 100644
--- a/test/test_argparse.py
+++ b/test/test_argparse.py
@@ -4077,10 +4077,22 @@ class TestAddFunction(TestCase):
         result = argparse.run(func, proc, args="proc monster".split())
         self.failUnlessEqual(('monster', '...'), result)
 
+    def test_runner_on_bound_functions(self):
+
+        class Bacon:
+            def proc(self, flying, spaghetti='...'):
+                return flying, spaghetti
+        
+        meat = Bacon()
+        result = argparse.run(meat.proc, args="monster".split())
+        self.failUnlessEqual(('monster', '...'), result)
+
     # only compile and test annotations if this is Python >= 3
     if sys.version_info[0] >= 3:
 
         def test_annotations(self):
+            # the function with annotations is a string to avoid syntax errors
+            # in python 2.x
             func_source = textwrap.dedent('''
                 def func(foo:bool, bar:int, spam:int=101):
                     return foo, bar