Reduce number of false positives emitted by non-iterator-returned checker

By disabling checker for cases when there're multiple possible values infered
for node. This way we lose some of the inference power, but throw a lot less
false positives.

Fixes issue #695.

2 files changed, 17 insertions, 13 deletions

diff --git a/pylint/test/functional/non_iterator_returned.py b/pylint/test/functional/non_iterator_returned.py
index 804ceee..d2fa758 100644
--- a/pylint/test/functional/non_iterator_returned.py
+++ b/pylint/test/functional/non_iterator_returned.py
@@ -56,6 +56,19 @@ class FifthGoodIterator(object):
     def __iter__(self):
         return IteratorClass
 
+class FileBasedIterator(object):
+    def __init__(self, path):
+        self.path = path
+        self.file = None
+
+    def __iter__(self):
+        if self.file is not None:
+            self.file.close()
+        self.file = open(self.path)
+        # self file has two infered values: None and <instance of 'file'>
+        # we don't want to emit error in this case
+        return self.file
+
 
 class FirstBadIterator(object):
     """ __iter__ returns a list """
@@ -80,11 +93,3 @@ class FourthBadIterator(object):
 
     def __iter__(self): # [non-iterator-returned]
         return ThirdBadIterator
-
-class FifthBadIterator(object):
-    """All branches should return an iterator."""
-
-    def __iter__(self): # [non-iterator-returned]
-        if self:
-            return 1
-        return SecondGoodIterator()
diff --git a/pylint/test/functional/non_iterator_returned.txt b/pylint/test/functional/non_iterator_returned.txt
index fe3db10..fa1d5be 100644
--- a/pylint/test/functional/non_iterator_returned.txt
+++ b/pylint/test/functional/non_iterator_returned.txt
@@ -1,5 +1,4 @@
-non-iterator-returned:63:FirstBadIterator.__iter__:__iter__ returns non-iterator
-non-iterator-returned:69:SecondBadIterator.__iter__:__iter__ returns non-iterator
-non-iterator-returned:75:ThirdBadIterator.__iter__:__iter__ returns non-iterator
-non-iterator-returned:81:FourthBadIterator.__iter__:__iter__ returns non-iterator
-non-iterator-returned:87:FifthBadIterator.__iter__:__iter__ returns non-iterator
\ No newline at end of file
+non-iterator-returned:76:FirstBadIterator.__iter__:__iter__ returns non-iterator
+non-iterator-returned:82:SecondBadIterator.__iter__:__iter__ returns non-iterator
+non-iterator-returned:88:ThirdBadIterator.__iter__:__iter__ returns non-iterator
+non-iterator-returned:94:FourthBadIterator.__iter__:__iter__ returns non-iterator