69 lines
2.1 KiB
Python
69 lines
2.1 KiB
Python
from .utils import _toposort, groupby
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class AmbiguityWarning(Warning):
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pass
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def supercedes(a, b):
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""" A is consistent and strictly more specific than B """
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return len(a) == len(b) and all(map(issubclass, a, b))
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def consistent(a, b):
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""" It is possible for an argument list to satisfy both A and B """
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return (len(a) == len(b) and
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all(issubclass(aa, bb) or issubclass(bb, aa)
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for aa, bb in zip(a, b)))
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def ambiguous(a, b):
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""" A is consistent with B but neither is strictly more specific """
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return consistent(a, b) and not (supercedes(a, b) or supercedes(b, a))
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def ambiguities(signatures):
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""" All signature pairs such that A is ambiguous with B """
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signatures = list(map(tuple, signatures))
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return {(a, b) for a in signatures for b in signatures
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if hash(a) < hash(b)
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and ambiguous(a, b)
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and not any(supercedes(c, a) and supercedes(c, b)
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for c in signatures)}
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def super_signature(signatures):
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""" A signature that would break ambiguities """
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n = len(signatures[0])
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assert all(len(s) == n for s in signatures)
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return [max([type.mro(sig[i]) for sig in signatures], key=len)[0]
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for i in range(n)]
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def edge(a, b, tie_breaker=hash):
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""" A should be checked before B
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Tie broken by tie_breaker, defaults to ``hash``
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"""
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if supercedes(a, b):
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if supercedes(b, a):
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return tie_breaker(a) > tie_breaker(b)
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else:
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return True
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return False
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def ordering(signatures):
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""" A sane ordering of signatures to check, first to last
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Topoological sort of edges as given by ``edge`` and ``supercedes``
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"""
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signatures = list(map(tuple, signatures))
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edges = [(a, b) for a in signatures for b in signatures if edge(a, b)]
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edges = groupby(lambda x: x[0], edges)
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for s in signatures:
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if s not in edges:
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edges[s] = []
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edges = {k: [b for a, b in v] for k, v in edges.items()}
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return _toposort(edges)
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