| u""" |
| Base classes for features that are backwards-incompatible. |
| |
| Usage: |
| features = Features() |
| features.add(Feature("py3k_feature", "power< 'py3k' any* >", "2.7")) |
| PATTERN = features.PATTERN |
| """ |
|
|
| pattern_unformatted = u"%s=%s" |
| message_unformatted = u""" |
| %s is only supported in Python %s and above.""" |
|
|
| class Feature(object): |
| u""" |
| A feature has a name, a pattern, and a minimum version of Python 2.x |
| required to use the feature (or 3.x if there is no backwards-compatible |
| version of 2.x) |
| """ |
| def __init__(self, name, PATTERN, version): |
| self.name = name |
| self._pattern = PATTERN |
| self.version = version |
|
|
| def message_text(self): |
| u""" |
| Format the above text with the name and minimum version required. |
| """ |
| return message_unformatted % (self.name, self.version) |
|
|
| class Features(set): |
| u""" |
| A set of features that generates a pattern for the features it contains. |
| This set will act like a mapping in that we map names to patterns. |
| """ |
| mapping = {} |
|
|
| def update_mapping(self): |
| u""" |
| Called every time we care about the mapping of names to features. |
| """ |
| self.mapping = dict([(f.name, f) for f in iter(self)]) |
|
|
| @property |
| def PATTERN(self): |
| u""" |
| Uses the mapping of names to features to return a PATTERN suitable |
| for using the lib2to3 patcomp. |
| """ |
| self.update_mapping() |
| return u" |\n".join([pattern_unformatted % (f.name, f._pattern) for f in iter(self)]) |
|
|
| def __getitem__(self, key): |
| u""" |
| Implement a simple mapping to get patterns from names. |
| """ |
| return self.mapping[key] |
|
|
