Add future 0.18.2

lib/libpasteurize/fixes/feature_base.py

@@ -0,0 +1,57 @@
+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" # name=pattern, for dict lookups
+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]