Added printing requirements

zope/interface/verify.py

@@ -0,0 +1,120 @@
+##############################################################################
+#
+# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""Verify interface implementations
+"""
+from zope.interface.exceptions import BrokenImplementation, DoesNotImplement
+from zope.interface.exceptions import BrokenMethodImplementation
+from types import FunctionType, MethodType
+from zope.interface.interface import fromMethod, fromFunction, Method
+import sys
+
+# This will be monkey-patched when running under Zope 2, so leave this
+# here:
+MethodTypes = (MethodType, )
+
+
+def _verify(iface, candidate, tentative=0, vtype=None):
+    """Verify that 'candidate' might correctly implements 'iface'.
+
+    This involves:
+
+      o Making sure the candidate defines all the necessary methods
+
+      o Making sure the methods have the correct signature
+
+      o Making sure the candidate asserts that it implements the interface
+
+    Note that this isn't the same as verifying that the class does
+    implement the interface.
+
+    If optional tentative is true, suppress the "is implemented by" test.
+    """
+
+    if vtype == 'c':
+        tester = iface.implementedBy
+    else:
+        tester = iface.providedBy
+
+    if not tentative and not tester(candidate):
+        raise DoesNotImplement(iface)
+
+    # Here the `desc` is either an `Attribute` or `Method` instance
+    for name, desc in iface.namesAndDescriptions(1):
+        try:
+            attr = getattr(candidate, name)
+        except AttributeError:
+            if (not isinstance(desc, Method)) and vtype == 'c':
+                # We can't verify non-methods on classes, since the
+                # class may provide attrs in it's __init__.
+                continue
+
+            raise BrokenImplementation(iface, name)
+
+        if not isinstance(desc, Method):
+            # If it's not a method, there's nothing else we can test
+            continue
+
+        if isinstance(attr, FunctionType):
+            if sys.version[0] == '3' and isinstance(candidate, type):
+                # This is an "unbound method" in Python 3.
+                meth = fromFunction(attr, iface, name=name,
+                                    imlevel=1) #pragma NO COVERAGE
+            else:
+                # Nope, just a normal function
+                meth = fromFunction(attr, iface, name=name)
+        elif (isinstance(attr, MethodTypes)
+              and type(attr.__func__) is FunctionType):
+            meth = fromMethod(attr, iface, name)
+        elif isinstance(attr, property) and vtype == 'c':
+            # We without an instance we cannot be sure it's not a
+            # callable.
+            continue
+        else:
+            if not callable(attr):
+                raise BrokenMethodImplementation(name, "Not a method")
+            # sigh, it's callable, but we don't know how to introspect it, so
+            # we have to give it a pass.
+            continue #pragma NO COVERAGE
+
+        # Make sure that the required and implemented method signatures are
+        # the same.
+        desc = desc.getSignatureInfo()
+        meth = meth.getSignatureInfo()
+
+        mess = _incompat(desc, meth)
+        if mess:
+            raise BrokenMethodImplementation(name, mess)
+
+    return True
+
+def verifyClass(iface, candidate, tentative=0):
+    return _verify(iface, candidate, tentative, vtype='c')
+
+def verifyObject(iface, candidate, tentative=0):
+    return _verify(iface, candidate, tentative, vtype='o')
+
+def _incompat(required, implemented):
+    #if (required['positional'] !=
+    #    implemented['positional'][:len(required['positional'])]
+    #    and implemented['kwargs'] is None):
+    #    return 'imlementation has different argument names'
+    if len(implemented['required']) > len(required['required']):
+        return 'implementation requires too many arguments'
+    if ((len(implemented['positional']) < len(required['positional']))
+        and not implemented['varargs']):
+        return "implementation doesn't allow enough arguments"
+    if required['kwargs'] and not implemented['kwargs']:
+        return "implementation doesn't support keyword arguments"
+    if required['varargs'] and not implemented['varargs']:
+        return "implementation doesn't support variable arguments"