Merged in PCManticore/pylint/iter (pull request #48)

Add new warning for non-iterators returned by __iter__

6 files changed, 148 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 71b8f40..3662602 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -8,6 +8,9 @@ ChangeLog for Pylint
       have basic input validation (bitbucket #53 and #54), patches provided by
       felipeochoa and Brian Lane
 
+    * Added a new warning, 'non-iterator-returned', for non-iterators 
+      returned by '__iter__'
+
 
 2013-08-06  --  1.0.0
 
diff --git a/checkers/classes.py b/checkers/classes.py
index 98a2f27..4c8022d 100644
--- a/checkers/classes.py
+++ b/checkers/classes.py
@@ -16,15 +16,21 @@
 """classes checker for Python code
 """
 from __future__ import generators
-
+import sys
 import astroid
 from astroid import YES, Instance, are_exclusive, AssAttr
+from astroid.bases import Generator
 
 from pylint.interfaces import IAstroidChecker
 from pylint.checkers import BaseChecker
 from pylint.checkers.utils import (PYMETHODS, overrides_a_method,
     check_messages, is_attr_private, is_attr_protected, node_frame_class)
 
+if sys.version_info >= (3, 0):
+    NEXT_METHOD = '__next__'
+else:
+    NEXT_METHOD = 'next'
+
 def class_is_abstract(node):
     """return true if the given class node should be considered as an abstract
     class
@@ -142,6 +148,11 @@ MSGS = {
               'non-parent-init-called',
               'Used when an __init__ method is called on a class which is not \
               in the direct ancestors for the analysed class.'),
+    'W0234': ('__iter__ returns non-iterator',
+              'non-iterator-returned',
+              'Used when an __iter__ method returns something which is not an \
+               iterable (i.e. has no `%s` method)' % NEXT_METHOD),
+
 
     }
 
@@ -311,6 +322,29 @@ a metaclass class method.'}
         except astroid.NotFoundError:
             pass
 
+        # check non-iterators in __iter__
+        if node.name == '__iter__':
+            self._check_iter(node)
+
+    def _check_iter(self, node):
+        try:
+            infered = node.infer_call_result(node)
+        except astroid.InferenceError:
+            return
+
+        for infered_node in infered:
+            if (infered_node is YES
+                or isinstance(infered_node, Generator)):
+                continue
+            if isinstance(infered_node, astroid.Instance):
+                try:
+                    infered_node.local_attr(NEXT_METHOD)
+                except astroid.NotFoundError:
+                    self.add_message('non-iterator-returned',
+                                     node=node)
+                    break
+
+
     def leave_function(self, node):
         """on method node, check if this method couldn't be a function
 
diff --git a/test/input/func_non_iterator_returned_py30.py b/test/input/func_non_iterator_returned_py30.py
new file mode 100644
index 0000000..6915768
--- /dev/null
+++ b/test/input/func_non_iterator_returned_py30.py
@@ -0,0 +1,52 @@
+"""Check non-iterators returned by __iter__ """
+
+# pylint: disable=too-few-public-methods
+
+__revision__ = 0
+
+class FirstGoodIterator(object):
+    """ yields in iterator. """
+
+    def __iter__(self):
+        for index in range(10):
+            yield index
+
+class SecondGoodIterator(object):
+    """ __iter__ and next """
+
+    def __iter__(self):
+        return self
+
+    def __next__(self): # pylint: disable=no-self-use
+        """ Infinite iterator, but still an iterator """
+        return 1
+
+class ThirdGoodIterator(object):
+    """ Returns other iterator, not the current instance """
+
+    def __iter__(self):
+        return SecondGoodIterator()
+
+class FourthGoodIterator(object):
+    """ __iter__ returns iter(...) """
+
+    def __iter__(self):
+        return iter(range(10))
+
+class FirstBadIterator(object):
+    """ __iter__ returns a list """
+
+    def __iter__(self):
+        return []
+
+class SecondBadIterator(object):
+    """ __iter__ without next """
+
+    def __iter__(self):
+        return self
+
+class ThirdBadIterator(object):
+    """ __iter__ returns an instance of another non-iterator """
+
+    def __iter__(self):
+        return SecondBadIterator()
diff --git a/test/input/func_non_iterator_returned_py_30.py b/test/input/func_non_iterator_returned_py_30.py
new file mode 100644
index 0000000..ff75941
--- /dev/null
+++ b/test/input/func_non_iterator_returned_py_30.py
@@ -0,0 +1,52 @@
+"""Check non-iterators returned by __iter__ """
+
+# pylint: disable=too-few-public-methods
+
+__revision__ = 0
+
+class FirstGoodIterator(object):
+    """ yields in iterator. """
+
+    def __iter__(self):
+        for index in range(10):
+            yield index
+
+class SecondGoodIterator(object):
+    """ __iter__ and next """
+
+    def __iter__(self):
+        return self
+
+    def next(self): # pylint: disable=no-self-use
+        """ Infinite iterator, but still an iterator """
+        return 1
+
+class ThirdGoodIterator(object):
+    """ Returns other iterator, not the current instance """
+
+    def __iter__(self):
+        return SecondGoodIterator()
+
+class FourthGoodIterator(object):
+    """ __iter__ returns iter(...) """
+
+    def __iter__(self):
+        return iter(range(10))
+
+class FirstBadIterator(object):
+    """ __iter__ returns a list """
+
+    def __iter__(self):
+        return []
+
+class SecondBadIterator(object):
+    """ __iter__ without next """
+
+    def __iter__(self):
+        return self
+
+class ThirdBadIterator(object):
+    """ __iter__ returns an instance of another non-iterator """
+
+    def __iter__(self):
+        return SecondBadIterator()
diff --git a/test/messages/func_non_iterator_returned_py30.txt b/test/messages/func_non_iterator_returned_py30.txt
new file mode 100644
index 0000000..b41b14b
--- /dev/null
+++ b/test/messages/func_non_iterator_returned_py30.txt
@@ -0,0 +1,3 @@
+W: 39:FirstBadIterator.__iter__: __iter__ returns non-iterator
+W: 45:SecondBadIterator.__iter__: __iter__ returns non-iterator
+W: 51:ThirdBadIterator.__iter__: __iter__ returns non-iterator
\ No newline at end of file
diff --git a/test/messages/func_non_iterator_returned_py_30.txt b/test/messages/func_non_iterator_returned_py_30.txt
new file mode 100644
index 0000000..b41b14b
--- /dev/null
+++ b/test/messages/func_non_iterator_returned_py_30.txt
@@ -0,0 +1,3 @@
+W: 39:FirstBadIterator.__iter__: __iter__ returns non-iterator
+W: 45:SecondBadIterator.__iter__: __iter__ returns non-iterator
+W: 51:ThirdBadIterator.__iter__: __iter__ returns non-iterator
\ No newline at end of file