fix and make common python version normalization

src/poetry/core/packages/dependency.py

@@ -16,6 +16,7 @@
 from poetry.core.packages.dependency_group import MAIN_GROUP
 from poetry.core.packages.specification import PackageSpecification
 from poetry.core.packages.utils.utils import contains_group_without_marker
+from poetry.core.packages.utils.utils import normalize_python_version_markers
 from poetry.core.semver.helpers import parse_constraint
 from poetry.core.semver.version_range_constraint import VersionRangeConstraint
 from poetry.core.version.markers import parse_marker
@@ -192,39 +193,10 @@ def marker(self, marker: str | BaseMarker) -> None:
         # Recalculate python versions.
         self._python_versions = "*"
         if not contains_group_without_marker(markers, "python_version"):
-            ors = []
-            for or_ in markers["python_version"]:
-                ands = []
-                for op, version in or_:
-                    # Expand python version
-                    if op == "==" and "*" not in version:
-                        version = "~" + version
-                        op = ""
-                    elif op == "!=":
-                        version += ".*"
-                    elif op in ("in", "not in"):
-                        versions = []
-                        for v in re.split("[ ,]+", version):
-                            split = v.split(".")
-                            if len(split) in [1, 2]:
-                                split.append("*")
-                                op_ = "" if op == "in" else "!="
-                            else:
-                                op_ = "==" if op == "in" else "!="
-
-                            versions.append(op_ + ".".join(split))
-
-                        glue = " || " if op == "in" else ", "
-                        if versions:
-                            ands.append(glue.join(versions))
-
-                        continue
-
-                    ands.append(f"{op}{version}")
-
-                ors.append(" ".join(ands))
-
-            self._python_versions = " || ".join(ors)
+            python_version_markers = markers["python_version"]
+            self._python_versions = normalize_python_version_markers(
+                python_version_markers
+            )
 
         self._python_constraint = parse_constraint(self._python_versions)
 

src/poetry/core/packages/utils/utils.py

@@ -15,13 +15,14 @@
 from urllib.request import url2pathname
 
 from poetry.core.pyproject.toml import PyProjectTOML
+from poetry.core.semver.helpers import parse_constraint
+from poetry.core.semver.version import Version
 from poetry.core.semver.version_range import VersionRange
 from poetry.core.version.markers import dnf
 
 
 if TYPE_CHECKING:
     from poetry.core.packages.constraints import BaseConstraint
-    from poetry.core.semver.version import Version
     from poetry.core.semver.version_constraint import VersionConstraint
     from poetry.core.semver.version_union import VersionUnion
     from poetry.core.version.markers import BaseMarker
@@ -206,7 +207,6 @@ def create_nested_marker(
     from poetry.core.packages.constraints.constraint import Constraint
     from poetry.core.packages.constraints.multi_constraint import MultiConstraint
     from poetry.core.packages.constraints.union_constraint import UnionConstraint
-    from poetry.core.semver.version import Version
     from poetry.core.semver.version_union import VersionUnion
 
     if constraint.is_any():
@@ -286,8 +286,6 @@ def get_python_constraint_from_marker(
     marker: BaseMarker,
 ) -> VersionConstraint:
     from poetry.core.semver.empty_constraint import EmptyConstraint
-    from poetry.core.semver.helpers import parse_constraint
-    from poetry.core.semver.version import Version
     from poetry.core.semver.version_range import VersionRange
 
     python_marker = marker.only("python_version", "python_full_version")
@@ -304,34 +302,58 @@ def get_python_constraint_from_marker(
         # which means that python_version is arbitrary for this group
         return VersionRange()
 
+    python_version_markers = markers["python_version"]
+    normalized = normalize_python_version_markers(python_version_markers)
+    constraint = parse_constraint(normalized)
+    return constraint
+
+
+def normalize_python_version_markers(  # NOSONAR
+    disjunction: list[list[tuple[str, str]]],
+) -> str:
     ors = []
-    for or_ in markers["python_version"]:
+    for or_ in disjunction:
         ands = []
         for op, version in or_:
             # Expand python version
-            if op == "==":
-                if "*" not in version:
-                    version = "~" + version
-                    op = ""
-            elif op == "!=":
-                if "*" not in version:
-                    version += ".*"
+            if op == "==" and "*" not in version:
+                version = "~" + version
+                op = ""
+
+            elif op == "!=" and "*" not in version:
+                version += ".*"
+
             elif op in ("<=", ">"):
+                # Make adjustments on encountering versions with less than full
+                # precision.
+                #
+                # Per PEP-508:
+                # python_version <-> '.'.join(platform.python_version_tuple()[:2])
+                #
+                # So for two digits of precision we make the following adjustments:
+                # - `python_version > "x.y"` requires version >= x.(y+1).anything
+                # - `python_version <= "x.y"` requires version < x.(y+1).anything
+                #
+                # Treatment when we see a single digit of precision is less clear: is
+                # that even a legitimate marker?
+                #
+                # Experiment suggests that pip behaviour is essentially to make a
+                # lexicographical comparison, for example `python_version > "3"` is
+                # satisfied by version 3.anything, whereas `python_version <= "3"` is
+                # satisfied only by version 2.anything.
+                #
+                # We achieve the above by fiddling with the operator and version in the
+                # marker.
                 parsed_version = Version.parse(version)
-                if parsed_version.precision == 1:
+                if parsed_version.precision < 3:
                     if op == "<=":
                         op = "<"
-                        version = parsed_version.next_major().text
                     elif op == ">":
                         op = ">="
-                        version = parsed_version.next_major().text
-                elif parsed_version.precision == 2:
-                    if op == "<=":
-                        op = "<"
-                        version = parsed_version.next_minor().text
-                    elif op == ">":
-                        op = ">="
-                        version = parsed_version.next_minor().text
+
+                if parsed_version.precision == 2:
+                    version = parsed_version.next_minor().text
+
             elif op in ("in", "not in"):
                 versions = []
                 for v in re.split("[ ,]+", version):
@@ -344,8 +366,8 @@ def get_python_constraint_from_marker(
 
                     versions.append(op_ + ".".join(split))
 
-                glue = " || " if op == "in" else ", "
                 if versions:
+                    glue = " || " if op == "in" else ", "
                     ands.append(glue.join(versions))
 
                 continue
@@ -354,4 +376,4 @@ def get_python_constraint_from_marker(
 
         ors.append(" ".join(ands))
 
-    return parse_constraint(" || ".join(ors))
+    return " || ".join(ors)

tests/packages/test_main.py

@@ -294,10 +294,10 @@ def test_dependency_from_pep_508_should_not_produce_empty_constraints_for_correc
 
     assert dep.name == "pytest-mypy"
     assert str(dep.constraint) == "*"
-    assert dep.python_versions == "<=3.10 >3"
+    assert dep.python_versions == "<3.11 >=3"
     assert dep.python_constraint.allows(Version.parse("3.6"))
-    assert dep.python_constraint.allows(Version.parse("3.10"))
-    assert not dep.python_constraint.allows(Version.parse("3"))
+    assert dep.python_constraint.allows(Version.parse("3.10.4"))
+    assert dep.python_constraint.allows(Version.parse("3"))
     assert dep.python_constraint.allows(Version.parse("3.0.1"))
     assert (
         str(dep.marker)

tests/packages/utils/test_utils.py

@@ -96,8 +96,8 @@ def test_convert_markers(
         ('python_version != "3.6.* "', "!=3.6.*"),
         # <, <=, >, >= precision 1
         ('python_version < "3"', "<3"),
-        ('python_version <= "3"', "<4"),
-        ('python_version > "3"', ">=4"),
+        ('python_version <= "3"', "<3"),
+        ('python_version > "3"', ">=3"),
         ('python_version >= "3"', ">=3"),
         # <, <=, >, >= precision 2
         ('python_version < "3.6"', "<3.6"),