Add '--ignore-constraint' option

news/7839.feature.rst

@@ -0,0 +1,3 @@
+Add the ``--ignore-constraint`` option to ``pip install``, ``pip download``
+and ``pip wheel`` commands to ignore an individual constraint from a
+constraints file.

src/pip/_internal/cli/cmdoptions.py

@@ -415,6 +415,19 @@ def constraints() -> Option:
     )
 
 
+def ignored_constraints() -> Option:
+    return Option(
+        "--ignore-constraint",
+        dest="ignored_constraints",
+        action="append",
+        default=[],
+        metavar="package",
+        help="Ignore constraints for given package. This is commonly used "
+        "during development of a package when using a common constraints "
+        "file. This option be used multiple times.",
+    )
+
+
 def requirements() -> Option:
     return Option(
         "-r",

src/pip/_internal/cli/req_command.py

@@ -363,10 +363,13 @@ def make_resolver(
                 ignore_requires_python=ignore_requires_python,
                 force_reinstall=force_reinstall,
                 upgrade_strategy=upgrade_strategy,
+                ignored_constraints=options.ignored_constraints,
                 py_version_info=py_version_info,
             )
         import pip._internal.resolution.legacy.resolver
 
+        # we intentionally don't pass ignored_constraints to this since the
+        # resolver is deprecated
         return pip._internal.resolution.legacy.resolver.Resolver(
             preparer=preparer,
             finder=finder,

src/pip/_internal/commands/download.py

@@ -37,6 +37,7 @@ class DownloadCommand(RequirementCommand):
 
     def add_options(self) -> None:
         self.cmd_opts.add_option(cmdoptions.constraints())
+        self.cmd_opts.add_option(cmdoptions.ignored_constraints())
         self.cmd_opts.add_option(cmdoptions.requirements())
         self.cmd_opts.add_option(cmdoptions.no_deps())
         self.cmd_opts.add_option(cmdoptions.global_options())

src/pip/_internal/commands/install.py

@@ -72,6 +72,7 @@ class InstallCommand(RequirementCommand):
     def add_options(self) -> None:
         self.cmd_opts.add_option(cmdoptions.requirements())
         self.cmd_opts.add_option(cmdoptions.constraints())
+        self.cmd_opts.add_option(cmdoptions.ignored_constraints())
         self.cmd_opts.add_option(cmdoptions.no_deps())
         self.cmd_opts.add_option(cmdoptions.pre())
 

src/pip/_internal/commands/wheel.py

@@ -61,6 +61,7 @@ def add_options(self) -> None:
         self.cmd_opts.add_option(cmdoptions.no_use_pep517())
         self.cmd_opts.add_option(cmdoptions.check_build_deps())
         self.cmd_opts.add_option(cmdoptions.constraints())
+        self.cmd_opts.add_option(cmdoptions.ignored_constraints())
         self.cmd_opts.add_option(cmdoptions.editable())
         self.cmd_opts.add_option(cmdoptions.requirements())
         self.cmd_opts.add_option(cmdoptions.src())

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

@@ -84,6 +84,8 @@ class PipProvider(_ProviderBase):
     :params upgrade_strategy: The user-specified upgrade strategy.
     :params user_requested: A set of canonicalized package names that the user
         supplied for pip to install/upgrade.
+    :params ignored_constraints: A list of canonicalized package names that the
+        user has asked us to ignore constraints for.
     """
 
     def __init__(
@@ -93,12 +95,14 @@ def __init__(
         ignore_dependencies: bool,
         upgrade_strategy: str,
         user_requested: Dict[str, int],
+        ignored_constraints: Sequence[str],
     ) -> None:
         self._factory = factory
         self._constraints = constraints
         self._ignore_dependencies = ignore_dependencies
         self._upgrade_strategy = upgrade_strategy
         self._user_requested = user_requested
+        self._ignored_constraints = ignored_constraints
         self._known_depths: Dict[str, float] = collections.defaultdict(lambda: math.inf)
 
     def identify(self, requirement_or_candidate: Union[Requirement, Candidate]) -> str:
@@ -223,11 +227,15 @@ def _eligible_for_upgrade(identifier: str) -> bool:
                 return user_order is not None
             return False
 
-        constraint = _get_with_identifier(
-            self._constraints,
-            identifier,
-            default=Constraint.empty(),
-        )
+        if identifier not in self._ignored_constraints:
+            constraint = _get_with_identifier(
+                self._constraints,
+                identifier,
+                default=Constraint.empty(),
+            )
+        else:
+            constraint = Constraint.empty()
+
         return self._factory.find_candidates(
             identifier=identifier,
             requirements=requirements,

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

@@ -2,7 +2,7 @@
 import functools
 import logging
 import os
-from typing import TYPE_CHECKING, Dict, List, Optional, Set, Tuple, cast
+from typing import TYPE_CHECKING, Dict, List, Optional, Sequence, Set, Tuple, cast
 
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.resolvelib import BaseReporter, ResolutionImpossible
@@ -50,6 +50,7 @@ def __init__(
         ignore_requires_python: bool,
         force_reinstall: bool,
         upgrade_strategy: str,
+        ignored_constraints: Sequence[str],
         py_version_info: Optional[Tuple[int, ...]] = None,
     ):
         super().__init__()
@@ -68,6 +69,7 @@ def __init__(
         )
         self.ignore_dependencies = ignore_dependencies
         self.upgrade_strategy = upgrade_strategy
+        self.ignored_constraints = ignored_constraints
         self._result: Optional[Result] = None
 
     def resolve(
@@ -80,6 +82,7 @@ def resolve(
             ignore_dependencies=self.ignore_dependencies,
             upgrade_strategy=self.upgrade_strategy,
             user_requested=collected.user_requested,
+            ignored_constraints=self.ignored_constraints,
         )
         if "PIP_RESOLVER_DEBUG" in os.environ:
             reporter: BaseReporter = PipDebuggingReporter()

tests/functional/test_new_resolver.py

@@ -681,6 +681,26 @@ def test_new_resolver_constraints(
     script.assert_not_installed("constraint_only")
 
 
+def test_new_resolver_constraint_ignored(script: PipTestEnvironment) -> None:
+    "We can ignore constraints. Useful when hacking on a constrained package."
+    create_basic_wheel_for_package(script, "pkg", "1.1.dev1")
+    constraints_file = script.scratch_path / "constraints.txt"
+    constraints_file.write_text("pkg==1.0")
+    script.pip(
+        "install",
+        "--no-cache-dir",
+        "--no-index",
+        "--find-links",
+        script.scratch_path,
+        "-c",
+        constraints_file,
+        "--ignore-constraint",
+        "pkg",
+        "pkg",
+    )
+    script.assert_installed(pkg="1.1.dev1")
+
+
 def test_new_resolver_constraint_no_specifier(script: PipTestEnvironment) -> None:
     "It's allowed (but useless...) for a constraint to have no specifier"
     create_basic_wheel_for_package(script, "pkg", "1.0")

tests/unit/resolution_resolvelib/conftest.py

@@ -75,4 +75,5 @@ def provider(factory: Factory) -> Iterator[PipProvider]:
         ignore_dependencies=False,
         upgrade_strategy="to-satisfy-only",
         user_requested={},
+        ignored_constraints=[],
     )

tests/unit/resolution_resolvelib/test_provider.py

@@ -36,6 +36,7 @@ def test_provider_known_depths(factory: Factory) -> None:
         ignore_dependencies=False,
         upgrade_strategy="to-satisfy-only",
         user_requested={root_requirement_name: 0},
+        ignored_constraints=[],
     )
 
     root_requirement_information = build_requirement_information(

tests/unit/resolution_resolvelib/test_resolver.py

@@ -29,6 +29,7 @@ def resolver(preparer: RequirementPreparer, finder: PackageFinder) -> Resolver:
         ignore_requires_python=False,
         force_reinstall=False,
         upgrade_strategy="to-satisfy-only",
+        ignored_constraints=[],
     )
     return resolver