58 lines
1.7 KiB
Python
58 lines
1.7 KiB
Python
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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" # name=pattern, for dict lookups
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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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