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Diffstat (limited to '.venv/lib/python3.12/site-packages/pip/_vendor/resolvelib/resolvers.py')
| -rw-r--r-- | .venv/lib/python3.12/site-packages/pip/_vendor/resolvelib/resolvers.py | 547 |
1 files changed, 547 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/pip/_vendor/resolvelib/resolvers.py b/.venv/lib/python3.12/site-packages/pip/_vendor/resolvelib/resolvers.py new file mode 100644 index 00000000..2c3d0e30 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/pip/_vendor/resolvelib/resolvers.py @@ -0,0 +1,547 @@ +import collections +import itertools +import operator + +from .providers import AbstractResolver +from .structs import DirectedGraph, IteratorMapping, build_iter_view + +RequirementInformation = collections.namedtuple( + "RequirementInformation", ["requirement", "parent"] +) + + +class ResolverException(Exception): + """A base class for all exceptions raised by this module. + + Exceptions derived by this class should all be handled in this module. Any + bubbling pass the resolver should be treated as a bug. + """ + + +class RequirementsConflicted(ResolverException): + def __init__(self, criterion): + super(RequirementsConflicted, self).__init__(criterion) + self.criterion = criterion + + def __str__(self): + return "Requirements conflict: {}".format( + ", ".join(repr(r) for r in self.criterion.iter_requirement()), + ) + + +class InconsistentCandidate(ResolverException): + def __init__(self, candidate, criterion): + super(InconsistentCandidate, self).__init__(candidate, criterion) + self.candidate = candidate + self.criterion = criterion + + def __str__(self): + return "Provided candidate {!r} does not satisfy {}".format( + self.candidate, + ", ".join(repr(r) for r in self.criterion.iter_requirement()), + ) + + +class Criterion(object): + """Representation of possible resolution results of a package. + + This holds three attributes: + + * `information` is a collection of `RequirementInformation` pairs. + Each pair is a requirement contributing to this criterion, and the + candidate that provides the requirement. + * `incompatibilities` is a collection of all known not-to-work candidates + to exclude from consideration. + * `candidates` is a collection containing all possible candidates deducted + from the union of contributing requirements and known incompatibilities. + It should never be empty, except when the criterion is an attribute of a + raised `RequirementsConflicted` (in which case it is always empty). + + .. note:: + This class is intended to be externally immutable. **Do not** mutate + any of its attribute containers. + """ + + def __init__(self, candidates, information, incompatibilities): + self.candidates = candidates + self.information = information + self.incompatibilities = incompatibilities + + def __repr__(self): + requirements = ", ".join( + "({!r}, via={!r})".format(req, parent) + for req, parent in self.information + ) + return "Criterion({})".format(requirements) + + def iter_requirement(self): + return (i.requirement for i in self.information) + + def iter_parent(self): + return (i.parent for i in self.information) + + +class ResolutionError(ResolverException): + pass + + +class ResolutionImpossible(ResolutionError): + def __init__(self, causes): + super(ResolutionImpossible, self).__init__(causes) + # causes is a list of RequirementInformation objects + self.causes = causes + + +class ResolutionTooDeep(ResolutionError): + def __init__(self, round_count): + super(ResolutionTooDeep, self).__init__(round_count) + self.round_count = round_count + + +# Resolution state in a round. +State = collections.namedtuple("State", "mapping criteria backtrack_causes") + + +class Resolution(object): + """Stateful resolution object. + + This is designed as a one-off object that holds information to kick start + the resolution process, and holds the results afterwards. + """ + + def __init__(self, provider, reporter): + self._p = provider + self._r = reporter + self._states = [] + + @property + def state(self): + try: + return self._states[-1] + except IndexError: + raise AttributeError("state") + + def _push_new_state(self): + """Push a new state into history. + + This new state will be used to hold resolution results of the next + coming round. + """ + base = self._states[-1] + state = State( + mapping=base.mapping.copy(), + criteria=base.criteria.copy(), + backtrack_causes=base.backtrack_causes[:], + ) + self._states.append(state) + + def _add_to_criteria(self, criteria, requirement, parent): + self._r.adding_requirement(requirement=requirement, parent=parent) + + identifier = self._p.identify(requirement_or_candidate=requirement) + criterion = criteria.get(identifier) + if criterion: + incompatibilities = list(criterion.incompatibilities) + else: + incompatibilities = [] + + matches = self._p.find_matches( + identifier=identifier, + requirements=IteratorMapping( + criteria, + operator.methodcaller("iter_requirement"), + {identifier: [requirement]}, + ), + incompatibilities=IteratorMapping( + criteria, + operator.attrgetter("incompatibilities"), + {identifier: incompatibilities}, + ), + ) + + if criterion: + information = list(criterion.information) + information.append(RequirementInformation(requirement, parent)) + else: + information = [RequirementInformation(requirement, parent)] + + criterion = Criterion( + candidates=build_iter_view(matches), + information=information, + incompatibilities=incompatibilities, + ) + if not criterion.candidates: + raise RequirementsConflicted(criterion) + criteria[identifier] = criterion + + def _remove_information_from_criteria(self, criteria, parents): + """Remove information from parents of criteria. + + Concretely, removes all values from each criterion's ``information`` + field that have one of ``parents`` as provider of the requirement. + + :param criteria: The criteria to update. + :param parents: Identifiers for which to remove information from all criteria. + """ + if not parents: + return + for key, criterion in criteria.items(): + criteria[key] = Criterion( + criterion.candidates, + [ + information + for information in criterion.information + if ( + information.parent is None + or self._p.identify(information.parent) not in parents + ) + ], + criterion.incompatibilities, + ) + + def _get_preference(self, name): + return self._p.get_preference( + identifier=name, + resolutions=self.state.mapping, + candidates=IteratorMapping( + self.state.criteria, + operator.attrgetter("candidates"), + ), + information=IteratorMapping( + self.state.criteria, + operator.attrgetter("information"), + ), + backtrack_causes=self.state.backtrack_causes, + ) + + def _is_current_pin_satisfying(self, name, criterion): + try: + current_pin = self.state.mapping[name] + except KeyError: + return False + return all( + self._p.is_satisfied_by(requirement=r, candidate=current_pin) + for r in criterion.iter_requirement() + ) + + def _get_updated_criteria(self, candidate): + criteria = self.state.criteria.copy() + for requirement in self._p.get_dependencies(candidate=candidate): + self._add_to_criteria(criteria, requirement, parent=candidate) + return criteria + + def _attempt_to_pin_criterion(self, name): + criterion = self.state.criteria[name] + + causes = [] + for candidate in criterion.candidates: + try: + criteria = self._get_updated_criteria(candidate) + except RequirementsConflicted as e: + self._r.rejecting_candidate(e.criterion, candidate) + causes.append(e.criterion) + continue + + # Check the newly-pinned candidate actually works. This should + # always pass under normal circumstances, but in the case of a + # faulty provider, we will raise an error to notify the implementer + # to fix find_matches() and/or is_satisfied_by(). + satisfied = all( + self._p.is_satisfied_by(requirement=r, candidate=candidate) + for r in criterion.iter_requirement() + ) + if not satisfied: + raise InconsistentCandidate(candidate, criterion) + + self._r.pinning(candidate=candidate) + self.state.criteria.update(criteria) + + # Put newly-pinned candidate at the end. This is essential because + # backtracking looks at this mapping to get the last pin. + self.state.mapping.pop(name, None) + self.state.mapping[name] = candidate + + return [] + + # All candidates tried, nothing works. This criterion is a dead + # end, signal for backtracking. + return causes + + def _backjump(self, causes): + """Perform backjumping. + + When we enter here, the stack is like this:: + + [ state Z ] + [ state Y ] + [ state X ] + .... earlier states are irrelevant. + + 1. No pins worked for Z, so it does not have a pin. + 2. We want to reset state Y to unpinned, and pin another candidate. + 3. State X holds what state Y was before the pin, but does not + have the incompatibility information gathered in state Y. + + Each iteration of the loop will: + + 1. Identify Z. The incompatibility is not always caused by the latest + state. For example, given three requirements A, B and C, with + dependencies A1, B1 and C1, where A1 and B1 are incompatible: the + last state might be related to C, so we want to discard the + previous state. + 2. Discard Z. + 3. Discard Y but remember its incompatibility information gathered + previously, and the failure we're dealing with right now. + 4. Push a new state Y' based on X, and apply the incompatibility + information from Y to Y'. + 5a. If this causes Y' to conflict, we need to backtrack again. Make Y' + the new Z and go back to step 2. + 5b. If the incompatibilities apply cleanly, end backtracking. + """ + incompatible_reqs = itertools.chain( + (c.parent for c in causes if c.parent is not None), + (c.requirement for c in causes), + ) + incompatible_deps = {self._p.identify(r) for r in incompatible_reqs} + while len(self._states) >= 3: + # Remove the state that triggered backtracking. + del self._states[-1] + + # Ensure to backtrack to a state that caused the incompatibility + incompatible_state = False + while not incompatible_state: + # Retrieve the last candidate pin and known incompatibilities. + try: + broken_state = self._states.pop() + name, candidate = broken_state.mapping.popitem() + except (IndexError, KeyError): + raise ResolutionImpossible(causes) + current_dependencies = { + self._p.identify(d) + for d in self._p.get_dependencies(candidate) + } + incompatible_state = not current_dependencies.isdisjoint( + incompatible_deps + ) + + incompatibilities_from_broken = [ + (k, list(v.incompatibilities)) + for k, v in broken_state.criteria.items() + ] + + # Also mark the newly known incompatibility. + incompatibilities_from_broken.append((name, [candidate])) + + # Create a new state from the last known-to-work one, and apply + # the previously gathered incompatibility information. + def _patch_criteria(): + for k, incompatibilities in incompatibilities_from_broken: + if not incompatibilities: + continue + try: + criterion = self.state.criteria[k] + except KeyError: + continue + matches = self._p.find_matches( + identifier=k, + requirements=IteratorMapping( + self.state.criteria, + operator.methodcaller("iter_requirement"), + ), + incompatibilities=IteratorMapping( + self.state.criteria, + operator.attrgetter("incompatibilities"), + {k: incompatibilities}, + ), + ) + candidates = build_iter_view(matches) + if not candidates: + return False + incompatibilities.extend(criterion.incompatibilities) + self.state.criteria[k] = Criterion( + candidates=candidates, + information=list(criterion.information), + incompatibilities=incompatibilities, + ) + return True + + self._push_new_state() + success = _patch_criteria() + + # It works! Let's work on this new state. + if success: + return True + + # State does not work after applying known incompatibilities. + # Try the still previous state. + + # No way to backtrack anymore. + return False + + def resolve(self, requirements, max_rounds): + if self._states: + raise RuntimeError("already resolved") + + self._r.starting() + + # Initialize the root state. + self._states = [ + State( + mapping=collections.OrderedDict(), + criteria={}, + backtrack_causes=[], + ) + ] + for r in requirements: + try: + self._add_to_criteria(self.state.criteria, r, parent=None) + except RequirementsConflicted as e: + raise ResolutionImpossible(e.criterion.information) + + # The root state is saved as a sentinel so the first ever pin can have + # something to backtrack to if it fails. The root state is basically + # pinning the virtual "root" package in the graph. + self._push_new_state() + + for round_index in range(max_rounds): + self._r.starting_round(index=round_index) + + unsatisfied_names = [ + key + for key, criterion in self.state.criteria.items() + if not self._is_current_pin_satisfying(key, criterion) + ] + + # All criteria are accounted for. Nothing more to pin, we are done! + if not unsatisfied_names: + self._r.ending(state=self.state) + return self.state + + # keep track of satisfied names to calculate diff after pinning + satisfied_names = set(self.state.criteria.keys()) - set( + unsatisfied_names + ) + + # Choose the most preferred unpinned criterion to try. + name = min(unsatisfied_names, key=self._get_preference) + failure_causes = self._attempt_to_pin_criterion(name) + + if failure_causes: + causes = [i for c in failure_causes for i in c.information] + # Backjump if pinning fails. The backjump process puts us in + # an unpinned state, so we can work on it in the next round. + self._r.resolving_conflicts(causes=causes) + success = self._backjump(causes) + self.state.backtrack_causes[:] = causes + + # Dead ends everywhere. Give up. + if not success: + raise ResolutionImpossible(self.state.backtrack_causes) + else: + # discard as information sources any invalidated names + # (unsatisfied names that were previously satisfied) + newly_unsatisfied_names = { + key + for key, criterion in self.state.criteria.items() + if key in satisfied_names + and not self._is_current_pin_satisfying(key, criterion) + } + self._remove_information_from_criteria( + self.state.criteria, newly_unsatisfied_names + ) + # Pinning was successful. Push a new state to do another pin. + self._push_new_state() + + self._r.ending_round(index=round_index, state=self.state) + + raise ResolutionTooDeep(max_rounds) + + +def _has_route_to_root(criteria, key, all_keys, connected): + if key in connected: + return True + if key not in criteria: + return False + for p in criteria[key].iter_parent(): + try: + pkey = all_keys[id(p)] + except KeyError: + continue + if pkey in connected: + connected.add(key) + return True + if _has_route_to_root(criteria, pkey, all_keys, connected): + connected.add(key) + return True + return False + + +Result = collections.namedtuple("Result", "mapping graph criteria") + + +def _build_result(state): + mapping = state.mapping + all_keys = {id(v): k for k, v in mapping.items()} + all_keys[id(None)] = None + + graph = DirectedGraph() + graph.add(None) # Sentinel as root dependencies' parent. + + connected = {None} + for key, criterion in state.criteria.items(): + if not _has_route_to_root(state.criteria, key, all_keys, connected): + continue + if key not in graph: + graph.add(key) + for p in criterion.iter_parent(): + try: + pkey = all_keys[id(p)] + except KeyError: + continue + if pkey not in graph: + graph.add(pkey) + graph.connect(pkey, key) + + return Result( + mapping={k: v for k, v in mapping.items() if k in connected}, + graph=graph, + criteria=state.criteria, + ) + + +class Resolver(AbstractResolver): + """The thing that performs the actual resolution work.""" + + base_exception = ResolverException + + def resolve(self, requirements, max_rounds=100): + """Take a collection of constraints, spit out the resolution result. + + The return value is a representation to the final resolution result. It + is a tuple subclass with three public members: + + * `mapping`: A dict of resolved candidates. Each key is an identifier + of a requirement (as returned by the provider's `identify` method), + and the value is the resolved candidate. + * `graph`: A `DirectedGraph` instance representing the dependency tree. + The vertices are keys of `mapping`, and each edge represents *why* + a particular package is included. A special vertex `None` is + included to represent parents of user-supplied requirements. + * `criteria`: A dict of "criteria" that hold detailed information on + how edges in the graph are derived. Each key is an identifier of a + requirement, and the value is a `Criterion` instance. + + The following exceptions may be raised if a resolution cannot be found: + + * `ResolutionImpossible`: A resolution cannot be found for the given + combination of requirements. The `causes` attribute of the + exception is a list of (requirement, parent), giving the + requirements that could not be satisfied. + * `ResolutionTooDeep`: The dependency tree is too deeply nested and + the resolver gave up. This is usually caused by a circular + dependency, but you can try to resolve this by increasing the + `max_rounds` argument. + """ + resolution = Resolution(self.provider, self.reporter) + state = resolution.resolve(requirements, max_rounds=max_rounds) + return _build_result(state) |