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venv/Lib/site-packages/pip/_vendor/resolvelib/__init__.py

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+__all__ = [
+    "__version__",
+    "AbstractProvider",
+    "AbstractResolver",
+    "BaseReporter",
+    "InconsistentCandidate",
+    "Resolver",
+    "RequirementsConflicted",
+    "ResolutionError",
+    "ResolutionImpossible",
+    "ResolutionTooDeep",
+]
+
+__version__ = "1.0.1"
+
+
+from .providers import AbstractProvider, AbstractResolver
+from .reporters import BaseReporter
+from .resolvers import (
+    InconsistentCandidate,
+    RequirementsConflicted,
+    ResolutionError,
+    ResolutionImpossible,
+    ResolutionTooDeep,
+    Resolver,
+)

venv/Lib/site-packages/pip/_vendor/resolvelib/compat/collections_abc.py

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+__all__ = ["Mapping", "Sequence"]
+
+try:
+    from collections.abc import Mapping, Sequence
+except ImportError:
+    from collections import Mapping, Sequence

venv/Lib/site-packages/pip/_vendor/resolvelib/providers.py

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+class AbstractProvider(object):
+    """Delegate class to provide the required interface for the resolver."""
+
+    def identify(self, requirement_or_candidate):
+        """Given a requirement, return an identifier for it.
+
+        This is used to identify a requirement, e.g. whether two requirements
+        should have their specifier parts merged.
+        """
+        raise NotImplementedError
+
+    def get_preference(
+        self,
+        identifier,
+        resolutions,
+        candidates,
+        information,
+        backtrack_causes,
+    ):
+        """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 identifier: An identifier as returned by ``identify()``. This
+            identifies the dependency matches which should be returned.
+        :param resolutions: Mapping of candidates currently pinned by the
+            resolver. Each key is an identifier, and the value is a candidate.
+            The candidate may conflict with requirements from ``information``.
+        :param candidates: Mapping of each dependency's possible candidates.
+            Each value is an iterator of candidates.
+        :param information: Mapping of requirement information of each package.
+            Each value is an iterator of *requirement information*.
+        :param backtrack_causes: Sequence of requirement information that were
+            the requirements that caused the resolver to most recently backtrack.
+
+        A *requirement information* instance is a named tuple with two members:
+
+        * ``requirement`` specifies a requirement contributing to the current
+          list of candidates.
+        * ``parent`` specifies the candidate that provides (depended on) the
+          requirement, or ``None`` to indicate a root requirement.
+
+        The preference could depend on various 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, identifier, requirements, incompatibilities):
+        """Find all possible candidates that satisfy the given constraints.
+
+        :param identifier: An identifier as returned by ``identify()``. This
+            identifies the dependency matches of which should be returned.
+        :param requirements: A mapping of requirements that all returned
+            candidates must satisfy. Each key is an identifier, and the value
+            an iterator of requirements for that dependency.
+        :param incompatibilities: A mapping of known incompatibilities of
+            each dependency. Each key is an identifier, and the value an
+            iterator of incompatibilities known to the resolver. All
+            incompatibilities *must* be excluded from the return value.
+
+        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.
+        """
+        raise NotImplementedError
+
+    def is_satisfied_by(self, requirement, candidate):
+        """Whether the given requirement can be satisfied by a candidate.
+
+        The candidate is guaranteed 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

venv/Lib/site-packages/pip/_vendor/resolvelib/reporters.py

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+class BaseReporter(object):
+    """Delegate class to provider progress reporting for the resolver."""
+
+    def starting(self):
+        """Called before the resolution actually starts."""
+
+    def starting_round(self, index):
+        """Called before each round of resolution starts.
+
+        The index is zero-based.
+        """
+
+    def ending_round(self, index, state):
+        """Called before each round of resolution ends.
+
+        This is NOT called if the resolution ends at this round. Use `ending`
+        if you want to report finalization. The index is zero-based.
+        """
+
+    def ending(self, state):
+        """Called before the resolution ends successfully."""
+
+    def adding_requirement(self, requirement, parent):
+        """Called when adding a new requirement into the resolve criteria.
+
+        :param requirement: The additional requirement to be applied to filter
+            the available candidaites.
+        :param parent: The candidate that requires ``requirement`` as a
+            dependency, or None if ``requirement`` is one of the root
+            requirements passed in from ``Resolver.resolve()``.
+        """
+
+    def resolving_conflicts(self, causes):
+        """Called when starting to attempt requirement conflict resolution.
+
+        :param causes: The information on the collision that caused the backtracking.
+        """
+
+    def rejecting_candidate(self, criterion, candidate):
+        """Called when rejecting a candidate during backtracking."""
+
+    def pinning(self, candidate):
+        """Called when adding a candidate to the potential solution."""

venv/Lib/site-packages/pip/_vendor/resolvelib/structs.py

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+import itertools
+
+from .compat import collections_abc
+
+
+class DirectedGraph(object):
+    """A graph structure with directed edges."""
+
+    def __init__(self):
+        self._vertices = set()
+        self._forwards = {}  # <key> -> Set[<key>]
+        self._backwards = {}  # <key> -> Set[<key>]
+
+    def __iter__(self):
+        return iter(self._vertices)
+
+    def __len__(self):
+        return len(self._vertices)
+
+    def __contains__(self, key):
+        return key in self._vertices
+
+    def copy(self):
+        """Return a shallow copy of this graph."""
+        other = DirectedGraph()
+        other._vertices = set(self._vertices)
+        other._forwards = {k: set(v) for k, v in self._forwards.items()}
+        other._backwards = {k: set(v) for k, v in self._backwards.items()}
+        return other
+
+    def add(self, key):
+        """Add a new vertex to the graph."""
+        if key in self._vertices:
+            raise ValueError("vertex exists")
+        self._vertices.add(key)
+        self._forwards[key] = set()
+        self._backwards[key] = set()
+
+    def remove(self, key):
+        """Remove a vertex from the graph, disconnecting all edges from/to it."""
+        self._vertices.remove(key)
+        for f in self._forwards.pop(key):
+            self._backwards[f].remove(key)
+        for t in self._backwards.pop(key):
+            self._forwards[t].remove(key)
+
+    def connected(self, f, t):
+        return f in self._backwards[t] and t in self._forwards[f]
+
+    def connect(self, f, t):
+        """Connect two existing vertices.
+
+        Nothing happens if the vertices are already connected.
+        """
+        if t not in self._vertices:
+            raise KeyError(t)
+        self._forwards[f].add(t)
+        self._backwards[t].add(f)
+
+    def iter_edges(self):
+        for f, children in self._forwards.items():
+            for t in children:
+                yield f, t
+
+    def iter_children(self, key):
+        return iter(self._forwards[key])
+
+    def iter_parents(self, key):
+        return iter(self._backwards[key])
+
+
+class IteratorMapping(collections_abc.Mapping):
+    def __init__(self, mapping, accessor, appends=None):
+        self._mapping = mapping
+        self._accessor = accessor
+        self._appends = appends or {}
+
+    def __repr__(self):
+        return "IteratorMapping({!r}, {!r}, {!r})".format(
+            self._mapping,
+            self._accessor,
+            self._appends,
+        )
+
+    def __bool__(self):
+        return bool(self._mapping or self._appends)
+
+    __nonzero__ = __bool__  # XXX: Python 2.
+
+    def __contains__(self, key):
+        return key in self._mapping or key in self._appends
+
+    def __getitem__(self, k):
+        try:
+            v = self._mapping[k]
+        except KeyError:
+            return iter(self._appends[k])
+        return itertools.chain(self._accessor(v), self._appends.get(k, ()))
+
+    def __iter__(self):
+        more = (k for k in self._appends if k not in self._mapping)
+        return itertools.chain(self._mapping, more)
+
+    def __len__(self):
+        more = sum(1 for k in self._appends if k not in self._mapping)
+        return len(self._mapping) + more
+
+
+class _FactoryIterableView(object):
+    """Wrap an iterator factory returned by `find_matches()`.
+
+    Calling `iter()` on this class would invoke the underlying iterator
+    factory, making it a "collection with ordering" that can be iterated
+    through multiple times, but lacks random access methods presented in
+    built-in Python sequence types.
+    """
+
+    def __init__(self, factory):
+        self._factory = factory
+        self._iterable = None
+
+    def __repr__(self):
+        return "{}({})".format(type(self).__name__, list(self))
+
+    def __bool__(self):
+        try:
+            next(iter(self))
+        except StopIteration:
+            return False
+        return True
+
+    __nonzero__ = __bool__  # XXX: Python 2.
+
+    def __iter__(self):
+        iterable = (
+            self._factory() if self._iterable is None else self._iterable
+        )
+        self._iterable, current = itertools.tee(iterable)
+        return current
+
+
+class _SequenceIterableView(object):
+    """Wrap an iterable returned by find_matches().
+
+    This is essentially just a proxy to the underlying sequence that provides
+    the same interface as `_FactoryIterableView`.
+    """
+
+    def __init__(self, sequence):
+        self._sequence = sequence
+
+    def __repr__(self):
+        return "{}({})".format(type(self).__name__, self._sequence)
+
+    def __bool__(self):
+        return bool(self._sequence)
+
+    __nonzero__ = __bool__  # XXX: Python 2.
+
+    def __iter__(self):
+        return iter(self._sequence)
+
+
+def build_iter_view(matches):
+    """Build an iterable view from the value returned by `find_matches()`."""
+    if callable(matches):
+        return _FactoryIterableView(matches)
+    if not isinstance(matches, collections_abc.Sequence):
+        matches = list(matches)
+    return _SequenceIterableView(matches)