Warn when legacy versions and specifiers are resolved

Also warn in pip check.

...

news/12063.removal.rst

@@ -0,0 +1,2 @@
+Deprecate legacy version and version specifiers that don't conform to `PEP 440
+<https://peps.python.org/pep-0440/>`_

src/pip/_internal/commands/check.py

@@ -7,6 +7,7 @@
 from pip._internal.operations.check import (
     check_package_set,
     create_package_set_from_installed,
+    warn_legacy_versions_and_specifiers,
 )
 from pip._internal.utils.misc import write_output
 
@@ -21,6 +22,7 @@ class CheckCommand(Command):
 
     def run(self, options: Values, args: List[str]) -> int:
         package_set, parsing_probs = create_package_set_from_installed()
+        warn_legacy_versions_and_specifiers(package_set)
         missing, conflicting = check_package_set(package_set)
 
         for project_name in missing:

src/pip/_internal/commands/download.py

@@ -130,6 +130,7 @@ def run(self, options: Values, args: List[str]) -> int:
         self.trace_basic_info(finder)
 
         requirement_set = resolver.resolve(reqs, check_supported_wheels=True)
+        requirement_set.warn_legacy_versions_and_specifiers()
 
         downloaded: List[str] = []
         for req in requirement_set.requirements.values():

src/pip/_internal/commands/install.py

@@ -387,6 +387,9 @@ def run(self, options: Values, args: List[str]) -> int:
                         json.dump(report.to_dict(), f, indent=2, ensure_ascii=False)
 
             if options.dry_run:
+                # In non dry-run mode, the legacy versions and specifiers check
+                # will be done as part of conflict detection.
+                requirement_set.warn_legacy_versions_and_specifiers()
                 would_install_items = sorted(
                     (r.metadata["name"], r.metadata["version"])
                     for r in requirement_set.requirements_to_install

src/pip/_internal/commands/wheel.py

@@ -145,6 +145,7 @@ def run(self, options: Values, args: List[str]) -> int:
         self.trace_basic_info(finder)
 
         requirement_set = resolver.resolve(reqs, check_supported_wheels=True)
+        requirement_set.warn_legacy_versions_and_specifiers()
 
         reqs_to_build: List[InstallRequirement] = []
         for req in requirement_set.requirements.values():

src/pip/_internal/operations/check.py

@@ -5,12 +5,15 @@
 from typing import Callable, Dict, List, NamedTuple, Optional, Set, Tuple
 
 from pip._vendor.packaging.requirements import Requirement
+from pip._vendor.packaging.specifiers import LegacySpecifier
 from pip._vendor.packaging.utils import NormalizedName, canonicalize_name
+from pip._vendor.packaging.version import LegacyVersion
 
 from pip._internal.distributions import make_distribution_for_install_requirement
 from pip._internal.metadata import get_default_environment
 from pip._internal.metadata.base import DistributionVersion
 from pip._internal.req.req_install import InstallRequirement
+from pip._internal.utils.deprecation import deprecated
 
 logger = logging.getLogger(__name__)
 
@@ -57,6 +60,8 @@ def check_package_set(
     package name and returns a boolean.
     """
 
+    warn_legacy_versions_and_specifiers(package_set)
+
     missing = {}
     conflicting = {}
 
@@ -147,3 +152,34 @@ def _create_whitelist(
                 break
 
     return packages_affected
+
+
+def warn_legacy_versions_and_specifiers(package_set: PackageSet) -> None:
+    for project_name, package_details in package_set.items():
+        if isinstance(package_details.version, LegacyVersion):
+            deprecated(
+                reason=(
+                    f"{project_name} {package_details.version} "
+                    f"has a non-standard version number."
+                ),
+                replacement=(
+                    f"to upgrade to a newer version of {project_name} "
+                    f"or contact the author to suggest that they "
+                    f"release a version with a conforming version number"
+                ),
+                gone_in="23.3",
+            )
+        for dep in package_details.dependencies:
+            if any(isinstance(spec, LegacySpecifier) for spec in dep.specifier):
+                deprecated(
+                    reason=(
+                        f"{project_name} {package_details.version} "
+                        f"has a non-standard dependency specifier {dep}."
+                    ),
+                    replacement=(
+                        f"to upgrade to a newer version of {project_name} "
+                        f"or contact the author to suggest that they "
+                        f"release a version with a conforming dependency specifiers"
+                    ),
+                    gone_in="23.3",
+                )

src/pip/_internal/req/req_set.py

@@ -2,9 +2,12 @@
 from collections import OrderedDict
 from typing import Dict, List
 
+from pip._vendor.packaging.specifiers import LegacySpecifier
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import LegacyVersion
 
 from pip._internal.req.req_install import InstallRequirement
+from pip._internal.utils.deprecation import deprecated
 
 logger = logging.getLogger(__name__)
 
@@ -80,3 +83,35 @@ def requirements_to_install(self) -> List[InstallRequirement]:
             for install_req in self.all_requirements
             if not install_req.constraint and not install_req.satisfied_by
         ]
+
+    def warn_legacy_versions_and_specifiers(self) -> None:
+        for req in self.requirements_to_install:
+            version = req.get_dist().version
+            if isinstance(version, LegacyVersion):
+                deprecated(
+                    reason=(
+                        f"pip has selected the non standard version {version} "
+                        f"of {req}. In the future this version will be "
+                        f"ignored as it isn't standard compliant."
+                    ),
+                    replacement=(
+                        "set or update constraints to select another version "
+                        "or contact the package author to fix the version number"
+                    ),
+                    gone_in="23.3",
+                )
+            for dep in req.get_dist().iter_dependencies():
+                if isinstance(dep.specifier, LegacySpecifier):
+                    deprecated(
+                        reason=(
+                            f"pip has selected {req} {version} which has non "
+                            f"standard dependency specifier {dep.specifier}. "
+                            f"In the future this version of {req} will be "
+                            f"ignored as it isn't standard compliant."
+                        ),
+                        replacement=(
+                            "set or update constraints to select another version "
+                            "or contact the package author to fix the version number"
+                        ),
+                        gone_in="23.3",
+                    )