Fix iteration of BTrees.items() in pure-python; and 3.6 support

Also fix ``list(proxy_btree.items())`` (or a list comprehension of the
same) in Python 3, which wants the ``__len__`` for a hint.

This is a central place to make sure these all behave consistently.

Fixes #20

Also drop pypy3

As a 3.2 implementation, it's not supported by pip anymore. There is a
much more recent version, 3.5-beta, but it's not on Travis yet. The
3.3-alpha which is on Travis is a dead end.

2 files changed, 68 insertions, 7 deletions

diff --git a/src/zope/security/checker.py b/src/zope/security/checker.py
index d5f261c..d75cfd5 100644
--- a/src/zope/security/checker.py
+++ b/src/zope/security/checker.py
@@ -770,6 +770,43 @@ if PYTHON2:
     _default_checkers[type({}.iterkeys())] = _iteratorChecker
     _default_checkers[type({}.itervalues())] = _iteratorChecker
 
+try:
+    import BTrees
+except ImportError: # pragma: no cover
+    pass
+else:
+    # The C implementation of BTree.items() is its own iterator
+    # and doesn't need any special entries to enable iteration.
+    # But the Python implementation has to call __iter__ to be able
+    # to do iteration. Whitelist it so that they behave the same.
+    # In addition, Python 3 will attempt to call __len__ on iterators
+    # for a length hint, so the C implementations also need to be
+    # added to the _iteratorChecker.
+    # We do this here so that all users of zope.security can benefit
+    # without knowing implementation details.
+    # See https://github.com/zopefoundation/zope.security/issues/20
+
+    def _fixup_btrees():
+        import BTrees._base
+        _default_checkers[BTrees._base._TreeItems] = _iteratorChecker
+
+        for name in ('IF', 'II', 'IO', 'OI', 'OO'):
+            for family_name in ('family32', 'family64'):
+                family = getattr(BTrees, family_name)
+                btree = getattr(family, name).BTree()
+
+                empty_type = type(btree.items())
+                if empty_type not in _default_checkers:
+                    _default_checkers[empty_type] = _iteratorChecker
+
+                btree[1] = 1
+                populated_type = type(btree.items())
+                if populated_type not in _default_checkers:
+                    _default_checkers[populated_type] = _iteratorChecker
+
+    _fixup_btrees()
+    del _fixup_btrees
+
 def _clear():
     _checkers.clear()
     _checkers.update(_default_checkers)
diff --git a/src/zope/security/tests/test_checker.py b/src/zope/security/tests/test_checker.py
index c5c01e7..d1bad49 100644
--- a/src/zope/security/tests/test_checker.py
+++ b/src/zope/security/tests/test_checker.py
@@ -17,13 +17,15 @@ import unittest
 
 def _skip_if_not_Py2(testfunc):
     import sys
-    from functools import update_wrapper
-    if sys.version_info[0] >= 3:
-        def dummy(self):
-            pass
-        update_wrapper(dummy, testfunc)
-        return dummy
-    return testfunc
+    return unittest.skipIf(sys.version_info[0] >= 3, "Needs Python 2")(testfunc)
+
+def _skip_if_no_btrees(testfunc):
+    try:
+        import BTrees
+    except ImportError:
+        return unittest.skip("BTrees is not installed")(testfunc)
+    else:
+        return testfunc
 
 class Test_ProxyFactory(unittest.TestCase):
 
@@ -389,6 +391,28 @@ class CheckerTestsBase(object):
         finally:
             _clear()
 
+    @_skip_if_no_btrees
+    def test_iteration_of_btree_items(self):
+        # iteration of BTree.items() is allowed by default.
+        from zope.security.proxy import Proxy
+        from zope.security.checker import Checker
+        from zope.security.checker import CheckerPublic
+        import BTrees
+
+        checker = Checker({'items': CheckerPublic})
+
+        for name in ('IF', 'II', 'IO', 'OI', 'OO'):
+            for family_name in ('family32', 'family64'):
+                family = getattr(BTrees, family_name)
+                btree = getattr(family, name).BTree()
+                proxy = Proxy(btree, checker)
+                # empty
+                self.assertEqual([], list(proxy.items()))
+
+                # With an object
+                btree[1] = 2
+                self.assertEqual([(1, 2)], list(proxy.items()))
+
 
 class CheckerPyTests(unittest.TestCase, CheckerTestsBase):