122 lines
3.7 KiB
Python
122 lines
3.7 KiB
Python
from .utils import _toposort, groupby
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from .variadic import isvariadic
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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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if len(a) < len(b):
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# only case is if a is empty and b is variadic
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return not a and len(b) == 1 and isvariadic(b[-1])
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elif len(a) == len(b):
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return all(map(issubclass, a, b))
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else:
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# len(a) > len(b)
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p1 = 0
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p2 = 0
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while p1 < len(a) and p2 < len(b):
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cur_a = a[p1]
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cur_b = b[p2]
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if not (isvariadic(cur_a) or isvariadic(cur_b)):
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if not issubclass(cur_a, cur_b):
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return False
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p1 += 1
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p2 += 1
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elif isvariadic(cur_a):
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assert p1 == len(a) - 1
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return p2 == len(b) - 1 and issubclass(cur_a, cur_b)
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elif isvariadic(cur_b):
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assert p2 == len(b) - 1
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if not issubclass(cur_a, cur_b):
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return False
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p1 += 1
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return p2 == len(b) - 1 and p1 == len(a)
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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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# Need to check for empty args
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if not a:
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return not b or isvariadic(b[0])
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if not b:
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return not a or isvariadic(a[0])
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# Non-empty args check for mutual subclasses
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if len(a) == len(b):
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return all(issubclass(aa, bb) or issubclass(bb, aa) for aa, bb in zip(a, b))
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else:
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p1 = 0
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p2 = 0
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while p1 < len(a) and p2 < len(b):
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cur_a = a[p1]
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cur_b = b[p2]
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if not issubclass(cur_b, cur_a) and not issubclass(cur_a, cur_b):
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return False
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if not (isvariadic(cur_a) or isvariadic(cur_b)):
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p1 += 1
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p2 += 1
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elif isvariadic(cur_a):
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p2 += 1
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elif isvariadic(cur_b):
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p1 += 1
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# We only need to check for variadic ends
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# Variadic types are guaranteed to be the last element
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return isvariadic(cur_a) and p2 == len(b) or isvariadic(cur_b) and p1 == len(a)
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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 set(
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(a, b)
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for a in signatures
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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) for c in signatures)
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)
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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] 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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# A either supercedes B and B does not supercede A or if B does then call
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# tie_breaker
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return supercedes(a, b) and (
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not supercedes(b, a) or tie_breaker(a) > tie_breaker(b)
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)
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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 = dict((k, [b for a, b in v]) for k, v in edges.items())
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return _toposort(edges)
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