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