109 lines
4.4 KiB
Python
109 lines
4.4 KiB
Python
class AbstractProvider(object):
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"""Delegate class to provide requirement interface for the resolver.
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"""
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def identify(self, dependency):
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"""Given a dependency, return an identifier for it.
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This is used in many places to identify the dependency, e.g. whether
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two requirements should have their specifier parts merged, whether
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two specifications would conflict with each other (because they the
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same name but different versions).
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"""
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raise NotImplementedError
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def get_preference(self, resolution, candidates, information):
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"""Produce a sort key for given specification based on preference.
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The preference is defined as "I think this requirement should be
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resolved first". The lower the return value is, the more preferred
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this group of arguments is.
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:param resolution: Currently pinned candidate, or `None`.
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:param candidates: A list of possible candidates.
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:param information: A list of requirement information.
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Each information instance is a named tuple with two entries:
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* `requirement` specifies a requirement contributing to the current
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candidate list
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* `parent` specifies the candidate that provides (dependend on) the
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requirement, or `None` to indicate a root requirement.
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The preference could depend on a various of issues, including (not
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necessarily in this order):
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* Is this package pinned in the current resolution result?
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* How relaxed is the requirement? Stricter ones should probably be
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worked on first? (I don't know, actually.)
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* How many possibilities are there to satisfy this requirement? Those
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with few left should likely be worked on first, I guess?
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* Are there any known conflicts for this requirement? We should
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probably work on those with the most known conflicts.
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A sortable value should be returned (this will be used as the `key`
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parameter of the built-in sorting function). The smaller the value is,
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the more preferred this specification is (i.e. the sorting function
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is called with `reverse=False`).
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"""
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raise NotImplementedError
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def find_matches(self, requirements):
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"""Find all possible candidates that satisfy the given requirements.
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This should try to get candidates based on the requirements' types.
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For VCS, local, and archive requirements, the one-and-only match is
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returned, and for a "named" requirement, the index(es) should be
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consulted to find concrete candidates for this requirement.
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:param requirements: A collection of requirements which all of the the
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returned candidates must match. All requirements are guaranteed to
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have the same identifier. The collection is never empty.
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:returns: An iterable that orders candidates by preference, e.g. the
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most preferred candidate should come first.
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"""
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raise NotImplementedError
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def is_satisfied_by(self, requirement, candidate):
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"""Whether the given requirement can be satisfied by a candidate.
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The candidate is guarenteed to have been generated from the
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requirement.
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A boolean should be returned to indicate whether `candidate` is a
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viable solution to the requirement.
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"""
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raise NotImplementedError
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def get_dependencies(self, candidate):
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"""Get dependencies of a candidate.
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This should return a collection of requirements that `candidate`
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specifies as its dependencies.
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"""
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raise NotImplementedError
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class AbstractResolver(object):
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"""The thing that performs the actual resolution work.
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"""
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base_exception = Exception
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def __init__(self, provider, reporter):
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self.provider = provider
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self.reporter = reporter
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def resolve(self, requirements, **kwargs):
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"""Take a collection of constraints, spit out the resolution result.
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This returns a representation of the final resolution state, with one
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guarenteed attribute ``mapping`` that contains resolved candidates as
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values. The keys are their respective identifiers.
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:param requirements: A collection of constraints.
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:param kwargs: Additional keyword arguments that subclasses may accept.
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:raises: ``self.base_exception`` or its subclass.
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"""
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raise NotImplementedError
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