Pick up hashes from contraints files and intersect

news/8792.bugfix

@@ -0,0 +1,2 @@
+New resolver: Pick up hash declarations in constraints files and use them to
+filter available distributions.

news/8839.bugfix

@@ -0,0 +1,3 @@
+New resolver: If a package appears multiple times in user specification with
+different ``--hash`` options, only hashes that present in all specifications
+should be allowed.

src/pip/_internal/resolution/resolvelib/base.py

@@ -1,5 +1,8 @@
+from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
 
+from pip._internal.req.req_install import InstallRequirement
+from pip._internal.utils.hashes import Hashes
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
@@ -8,7 +11,6 @@
     from pip._vendor.packaging.version import _BaseVersion
 
     from pip._internal.models.link import Link
-    from pip._internal.req.req_install import InstallRequirement
 
     CandidateLookup = Tuple[
         Optional["Candidate"],
@@ -24,6 +26,39 @@ def format_name(project, extras):
     return "{}[{}]".format(project, ",".join(canonical_extras))
 
 
+class Constraint(object):
+    def __init__(self, specifier, hashes):
+        # type: (SpecifierSet, Hashes) -> None
+        self.specifier = specifier
+        self.hashes = hashes
+
+    @classmethod
+    def empty(cls):
+        # type: () -> Constraint
+        return Constraint(SpecifierSet(), Hashes())
+
+    @classmethod
+    def from_ireq(cls, ireq):
+        # type: (InstallRequirement) -> Constraint
+        return Constraint(ireq.specifier, ireq.hashes(trust_internet=False))
+
+    def __nonzero__(self):
+        # type: () -> bool
+        return bool(self.specifier) or bool(self.hashes)
+
+    def __bool__(self):
+        # type: () -> bool
+        return self.__nonzero__()
+
+    def __and__(self, other):
+        # type: (InstallRequirement) -> Constraint
+        if not isinstance(other, InstallRequirement):
+            return NotImplemented
+        specifier = self.specifier & other.specifier
+        hashes = self.hashes & other.hashes(trust_internet=False)
+        return Constraint(specifier, hashes)
+
+
 class Requirement(object):
     @property
     def name(self):

src/pip/_internal/resolution/resolvelib/factory.py

@@ -22,6 +22,7 @@
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
+from .base import Constraint
 from .candidates import (
     AlreadyInstalledCandidate,
     EditableCandidate,
@@ -152,6 +153,7 @@ def _iter_found_candidates(
         self,
         ireqs,  # type: Sequence[InstallRequirement]
         specifier,  # type: SpecifierSet
+        hashes,  # type: Hashes
     ):
         # type: (...) -> Iterable[Candidate]
         if not ireqs:
@@ -164,11 +166,10 @@ def _iter_found_candidates(
         template = ireqs[0]
         name = canonicalize_name(template.req.name)
 
-        hashes = Hashes()
         extras = frozenset()  # type: FrozenSet[str]
         for ireq in ireqs:
             specifier &= ireq.req.specifier
-            hashes |= ireq.hashes(trust_internet=False)
+            hashes &= ireq.hashes(trust_internet=False)
             extras |= frozenset(ireq.extras)
 
         # We use this to ensure that we only yield a single candidate for
@@ -218,7 +219,7 @@ def _iter_found_candidates(
         return six.itervalues(candidates)
 
     def find_candidates(self, requirements, constraint):
-        # type: (Sequence[Requirement], SpecifierSet) -> Iterable[Candidate]
+        # type: (Sequence[Requirement], Constraint) -> Iterable[Candidate]
         explicit_candidates = set()  # type: Set[Candidate]
         ireqs = []  # type: List[InstallRequirement]
         for req in requirements:
@@ -231,7 +232,11 @@ def find_candidates(self, requirements, constraint):
         # If none of the requirements want an explicit candidate, we can ask
         # the finder for candidates.
         if not explicit_candidates:
-            return self._iter_found_candidates(ireqs, constraint)
+            return self._iter_found_candidates(
+                ireqs,
+                constraint.specifier,
+                constraint.hashes,
+            )
 
         if constraint:
             name = explicit_candidates.pop().name

src/pip/_internal/resolution/resolvelib/provider.py

@@ -1,8 +1,9 @@
-from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.resolvelib.providers import AbstractProvider
 
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
+from .base import Constraint
+
 if MYPY_CHECK_RUNNING:
     from typing import (
         Any,
@@ -41,7 +42,7 @@ class PipProvider(AbstractProvider):
     def __init__(
         self,
         factory,  # type: Factory
-        constraints,  # type: Dict[str, SpecifierSet]
+        constraints,  # type: Dict[str, Constraint]
         ignore_dependencies,  # type: bool
         upgrade_strategy,  # type: str
         user_requested,  # type: Set[str]
@@ -134,7 +135,7 @@ def find_matches(self, requirements):
         if not requirements:
             return []
         constraint = self._constraints.get(
-            requirements[0].name, SpecifierSet(),
+            requirements[0].name, Constraint.empty(),
         )
         candidates = self._factory.find_candidates(requirements, constraint)
         return reversed(self._sort_matches(candidates))

src/pip/_internal/resolution/resolvelib/resolver.py

@@ -14,12 +14,12 @@
 from pip._internal.utils.misc import dist_is_editable
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
+from .base import Constraint
 from .factory import Factory
 
 if MYPY_CHECK_RUNNING:
     from typing import Dict, List, Optional, Set, Tuple
 
-    from pip._vendor.packaging.specifiers import SpecifierSet
     from pip._vendor.resolvelib.resolvers import Result
     from pip._vendor.resolvelib.structs import Graph
 
@@ -71,7 +71,7 @@ def __init__(
     def resolve(self, root_reqs, check_supported_wheels):
         # type: (List[InstallRequirement], bool) -> RequirementSet
 
-        constraints = {}  # type: Dict[str, SpecifierSet]
+        constraints = {}  # type: Dict[str, Constraint]
         user_requested = set()  # type: Set[str]
         requirements = []
         for req in root_reqs:
@@ -84,9 +84,9 @@ def resolve(self, root_reqs, check_supported_wheels):
                     continue
                 name = canonicalize_name(req.name)
                 if name in constraints:
-                    constraints[name] = constraints[name] & req.specifier
+                    constraints[name] &= req
                 else:
-                    constraints[name] = req.specifier
+                    constraints[name] = Constraint.from_ireq(req)
             else:
                 if req.user_supplied and req.name:
                     user_requested.add(canonicalize_name(req.name))

src/pip/_internal/utils/hashes.py

@@ -46,16 +46,24 @@ def __init__(self, hashes=None):
         """
         self._allowed = {} if hashes is None else hashes
 
-    def __or__(self, other):
+    def __and__(self, other):
         # type: (Hashes) -> Hashes
         if not isinstance(other, Hashes):
             return NotImplemented
-        new = self._allowed.copy()
+
+        # If either of the Hashes object is entirely empty (i.e. no hash
+        # specified at all), all hashes from the other object are allowed.
+        if not other:
+            return self
+        if not self:
+            return other
+
+        # Otherwise only hashes that present in both objects are allowed.
+        new = {}
         for alg, values in iteritems(other._allowed):
-            try:
-                new[alg] += values
-            except KeyError:
-                new[alg] = values
+            if alg not in self._allowed:
+                continue
+            new[alg] = [v for v in values if v in self._allowed[alg]]
         return Hashes(new)
 
     @property