99 lines
2.3 KiB
Python
99 lines
2.3 KiB
Python
"""
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Various error handling helpers
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See https://beepb00p.xyz/mypy-error-handling.html#kiss for more detail
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"""
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from itertools import tee
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from typing import Union, TypeVar, Iterable, List, Tuple, Type
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T = TypeVar('T')
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E = TypeVar('E', bound=Exception) # TODO make covariant?
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ResT = Union[T, E]
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Res = ResT[T, Exception]
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def unwrap(res: Res[T]) -> T:
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if isinstance(res, Exception):
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raise res
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else:
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return res
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def echain(ex: E, cause: Exception) -> E:
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ex.__cause__ = cause
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return ex
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def split_errors(l: Iterable[ResT[T, E]], ET: Type[E]) -> Tuple[Iterable[T], Iterable[E]]:
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# TODO would be nice to have ET=Exception default?
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vit, eit = tee(l)
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# TODO ugh, not sure if I can reconcile type checking and runtime and convince mypy that ET and E are the same type?
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values: Iterable[T] = (
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r # type: ignore[misc]
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for r in vit
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if not isinstance(r, ET))
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errors: Iterable[E] = (
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r
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for r in eit
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if isinstance(r, ET))
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# TODO would be interesting to be able to have yield statement anywehere in code
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# so there are multiple 'entry points' to the return value
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return (values, errors)
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def sort_res_by(items: Iterable[ResT], key) -> List[ResT]:
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"""
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The general idea is: just alaways carry errors with the entry that precedes them
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"""
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# TODO ResT object should hold exception class?...
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group = []
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groups = []
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for i in items:
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if isinstance(i, Exception):
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group.append(i)
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else:
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groups.append((i, group))
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group = []
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results = []
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for v, errs in sorted(groups, key=lambda p: key(p[0])):
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results.extend(errs)
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results.append(v)
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results.extend(group)
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return results
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def test_sort_res_by():
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class Exc(Exception):
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def __eq__(self, other):
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return self.args == other.args
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ress = [
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Exc('first'),
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Exc('second'),
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5,
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3,
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Exc('xxx'),
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2,
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1,
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Exc('last'),
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]
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results = sort_res_by(ress, lambda x: x) # type: ignore
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assert results == [
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1,
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Exc('xxx'),
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2,
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3,
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Exc('first'),
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Exc('second'),
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5,
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Exc('last'),
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]
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results2 = sort_res_by(ress + [0], lambda x: x) # type: ignore
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assert results2 == [Exc('last'), 0] + results[:-1]
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