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