Merge pull request #73 from zopefoundation/consistent-interfaces

Ensure all objects have consistent interface resolution orders.

.gitignore

@@ -1,4 +1,5 @@
 *.pyc
+*.pyo
 *.so
 __pycache__
 *.egg

.travis.yml

@@ -5,6 +5,7 @@ env:
     TWINE_USERNAME: zope.wheelbuilder
     TWINE_PASSWORD:
       secure: "U6CeZtNEPDN3qKXfrLcvHFLrowqNWxmapXLWygZRxKgfR+ypowe1Y0a4kCBEBZKtysbY26MmIkrMV07tEMxny1yUWVCvRvUaQw0Ic3t5CM0R019zjVh9fQUTdWGCwri86Qj/OaeuPeMR0LCr6d9nMSun0GWSWhjOUhkTCdchfQw="
+    ZOPE_INTERFACE_STRICT_IRO: 1
 
 python:
   - 2.7

CHANGES.rst

@@ -2,10 +2,12 @@
  Changes
 =========
 
-5.2.0 (unreleased)
+5.1.1 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Ensure all objects have consistent interface resolution orders (if
+  all dependencies are up-to-date). See `issue 71
+  <https://github.com/zopefoundation/zope.security/issues/71>`_.
 
 
 5.1.0 (2020-02-14)

setup.py

@@ -127,7 +127,7 @@ def __str__(self):
 
 
 setup(name='zope.security',
-      version='5.2.0.dev0',
+      version='5.1.1.dev0',
       author='Zope Foundation and Contributors',
       author_email='zope-dev@zope.org',
       description='Zope Security Framework',

src/zope/security/_compat.py

@@ -39,4 +39,25 @@
     PYTHON2 = False
 
 
-_BLANK = u''
+class implementer_if_needed(object):
+    # Helper to make sure we don't redundantly implement interfaces
+    # already inherited. Doing so tends to produce problems with the
+    # C3 order. Even though here we could easily statically determine
+    # if we need the interface or not, this is used for clarity, to
+    # reduce the testing load, and to insulate against changes in
+    # super classes.
+    def __init__(self, *ifaces):
+        self._ifaces = ifaces
+
+    def __call__(self, cls):
+        from zope.interface import implementedBy
+        from zope.interface import implementer
+
+        ifaces_needed = []
+        implemented = implementedBy(cls)
+        ifaces_needed = [
+            iface
+            for iface in self._ifaces
+            if not implemented.isOrExtends(iface)
+        ]
+        return implementer(*ifaces_needed)(cls)

src/zope/security/checker.py

@@ -82,6 +82,7 @@
 from zope.security._compat import CLASS_TYPES
 from zope.security._compat import PYTHON2
 from zope.security._compat import PURE_PYTHON
+from zope.security._compat import implementer_if_needed
 from zope.security.proxy import Proxy
 from zope.security.proxy import getChecker
 
@@ -503,7 +504,7 @@ def undefineChecker(type_):
 
 _getChecker = _checkers.get
 
-@implementer(IChecker)
+@implementer_if_needed(IChecker)
 class CombinedChecker(Checker):
     """A checker that combines two other checkers in a logical-or fashion.
 

src/zope/security/zcml.py

@@ -18,21 +18,22 @@
 from zope.configuration.fields import GlobalObject
 from zope.configuration.fields import MessageID
 from zope.interface import Interface
-from zope.interface import implementer
 from zope.schema import Id
 from zope.schema.interfaces import IFromUnicode
 
+from zope.security._compat import implementer_if_needed
 from zope.security.permission import checkPermission
 from zope.security.management import setSecurityPolicy
 from zope.security.interfaces import PUBLIC_PERMISSION_NAME as zope_Public
 
-@implementer(IFromUnicode)
+
+@implementer_if_needed(IFromUnicode)
 class Permission(Id):
     r"""This field describes a permission.
     """
 
-    def fromUnicode(self, u):
-        u = super(Permission, self).fromUnicode(u)
+    def fromUnicode(self, value):
+        u = super(Permission, self).fromUnicode(value)
 
         map = getattr(self.context, 'permission_mapping', {})
         return map.get(u, u)

tox.ini

@@ -13,28 +13,10 @@ extras =
     test
     docs
 deps =
-
-[testenv:py27-watch]
-basepython =
-    python2.7
-setenv =
-    PURE_PYTHON = 1
-    ZOPE_WATCH_CHECKERS = 1
-    PIP_CACHE_DIR = {envdir}/.cache
-
-[testenv:py37-watch]
-basepython =
-    python3.7
-setenv =
-    ZOPE_WATCH_CHECKERS = 1
-    PIP_CACHE_DIR = {envdir}/.cache
-
-[testenv:py37-pure]
-basepython =
-    python3.7
 setenv =
-    PURE_PYTHON = 1
-    PIP_CACHE_DIR = {envdir}/.cache
+    ZOPE_INTERFACE_STRICT_IRO = 1
+    watch: ZOPE_WATCH_CHECKERS = 1
+    pure: PURE_PYTHON = 1
 
 [testenv:coverage]
 usedevelop = true