diff options
Diffstat (limited to 'src/zope/interface/declarations.py')
| -rw-r--r-- | src/zope/interface/declarations.py | 35 |
1 files changed, 25 insertions, 10 deletions
diff --git a/src/zope/interface/declarations.py b/src/zope/interface/declarations.py index 935b026..de90074 100644 --- a/src/zope/interface/declarations.py +++ b/src/zope/interface/declarations.py @@ -115,20 +115,35 @@ class Declaration(Specification): ]) def __add__(self, other): - """Add two specifications or a specification and an interface """ - seen = {} - result = [] - for i in self.interfaces(): - seen[i] = 1 - result.append(i) + Add two specifications or a specification and an interface + and produce a new declaration. + + .. versionchanged:: 5.4.0 + Now tries to preserve a consistent resolution order. Interfaces + being added to this object are added to the front of the resulting resolution + order if they already extend an interface in this object. Previously, + they were always added to the end of the order, which easily resulted in + invalid orders. + """ + before = [] + result = list(self.interfaces()) + seen = set(result) for i in other.interfaces(): - if i not in seen: - seen[i] = 1 + if i in seen: + continue + seen.add(i) + if any(i.extends(x) for x in result): + # It already extends us, e.g., is a subclass, + # so it needs to go at the front of the RO. + before.append(i) + else: result.append(i) + return Declaration(*(before + result)) - return Declaration(*result) - + # XXX: Is __radd__ needed? No tests break if it's removed. + # If it is needed, does it need to handle the C3 ordering differently? + # I (JAM) don't *think* it does. __radd__ = __add__ @staticmethod |