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Simplify suffix_union function #531

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Simplify suffix_union function #531

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f567e46
Simplify suffix_union function
maresb Oct 16, 2023
e1ead32
Change suffix_union to raise ValueError
maresb Oct 16, 2023
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40 changes: 22 additions & 18 deletions conda_lock/common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -79,9 +79,7 @@ def ordered_union(collections: Iterable[Iterable[T]]) -> List[T]:
return list({k: k for k in chain.from_iterable(collections)}.values())


def suffix_union(
collections: Iterable[Sequence["SupportsRichComparisonT"]],
) -> List["SupportsRichComparisonT"]:
def suffix_union(collections: Iterable[Sequence]) -> List:
"""Generates the union of sequence ensuring that they have a common suffix.

This is used to unify channels.
Expand All @@ -92,25 +90,31 @@ def suffix_union(
>>> suffix_union([[1], [2, 1], [4, 1]])
Traceback (most recent call last)
...
RuntimeError: [4, 1] is not a subset of [2, 1]
ValueError: [4, 1] is not an ordered subset of [2, 1]

"""
from genericpath import commonprefix
return list(reversed(prefix_union([list(reversed(s)) for s in collections])))

result: List["SupportsRichComparisonT"] = []

def prefix_union(collections: Iterable[Sequence]) -> List:
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@jacksmith15 jacksmith15 Oct 16, 2023 •
edited
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Seems an improvement to me!

I wonder if part of the confusion has stemmed from the generic naming of these functions.

Could it be instead called unify_package_sources or merge_package_sources?

FWIW the way I reason about this logic is a bit different, not sure if this is more or less confusing to others (probably a tad less performant):

def unify_package_sources(collections: Iterable[Sequence[str]]) -> List[str]:
    result = max(collections, key=len)
    for collection in collections:
        if collection != result[-len(collection):]:
            raise ValueError(f"{collection} is not an ordered subset of {result}")
    return result

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Nice!! I think there's an edge case when len(collection) == 0. But making sure that's in order, would you like to make a PR to supersede mine?

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Happy to do so 👍

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#532

"""Generates the union of sequence ensuring that they have a common prefix.

>>> prefix_union([[1], [1, 2], [1, 2, 3], [1, 2], [1]])
[1, 2, 3]

>>> prefix_union([[1], [1, 2], [1, 4]])
Traceback (most recent call last)
...
ValueError: [1, 4] is not an ordered subset of [1, 2]
"""
result: List = []
for seq in collections:
if seq:
rev_priority = list(reversed(seq))
prefix = commonprefix([result, rev_priority]) # type: ignore
if len(result) == 0:
result = rev_priority
elif prefix[: len(rev_priority)] != result[: len(rev_priority)]:
raise ValueError(
f"{list(reversed(rev_priority))} is not a ordered subset of {list(reversed(result))}"
)
elif len(rev_priority) > len(result):
result = rev_priority
return list(reversed(result))
for i, item in enumerate(seq):
if i >= len(result):
result.append(item)
elif result[i] != item:
raise ValueError(f"{seq} is not an ordered subset of {result}")
return result


def relative_path(source: pathlib.Path, target: pathlib.Path) -> str:
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