fix construction of python version marker

src/poetry/core/packages/package.py

@@ -15,7 +15,6 @@
 from poetry.core.packages.dependency_group import MAIN_GROUP
 from poetry.core.packages.specification import PackageSpecification
 from poetry.core.packages.utils.utils import create_nested_marker
-from poetry.core.packages.utils.utils import get_python_constraint_from_marker
 from poetry.core.semver.helpers import parse_constraint
 from poetry.core.version.markers import parse_marker
 
@@ -263,11 +262,10 @@ def python_versions(self) -> str:
     @python_versions.setter
     def python_versions(self, value: str) -> None:
         self._python_versions = value
-        constraint = parse_constraint(value)
+        self._python_constraint = parse_constraint(value)
         self._python_marker = parse_marker(
-            create_nested_marker("python_version", constraint)
+            create_nested_marker("python_version", self._python_constraint)
         )
-        self._python_constraint = get_python_constraint_from_marker(self._python_marker)
 
     @property
     def python_constraint(self) -> VersionConstraint:

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

@@ -240,44 +240,53 @@ def create_nested_marker(
         marker = f'{name} == "{constraint.text}"'
     else:
         assert isinstance(constraint, VersionRange)
+        min_name = max_name = name
+
+        parts = []
+
+        # `python_version` is a special case: to keep the constructed marker equivalent
+        # to the constraint we need to be careful with the precision.
+        #
+        # PEP 440 tells us that that when we come to make the comparison the release
+        # segment will be zero padded: eg "<= 3.10" is equivalent to "<= 3.10.0".
+        #
+        # But "python_version <= 3.6" is _not_ equivalent to "python_version <= 3.10.0" -
+        # see normalize_python_version_markers.
+        #
+        # A similar issue arises for a constraint like "> 3.6".
         if constraint.min is not None:
-            op = ">="
-            if not constraint.include_min:
-                op = ">"
-
+            op = ">=" if constraint.include_min else ">"
             version = constraint.min
-            if constraint.max is not None:
-                min_name = max_name = name
-                if min_name == "python_version" and constraint.min.precision >= 3:
-                    min_name = "python_full_version"
-
-                if max_name == "python_version" and constraint.max.precision >= 3:
-                    max_name = "python_full_version"
-
-                text = f'{min_name} {op} "{version}"'
-
-                op = "<="
-                if not constraint.include_max:
-                    op = "<"
+            if min_name == "python_version" and version.precision >= 3:
+                min_name = "python_full_version"
 
-                version = constraint.max
+            if min_name == "python_version" and not constraint.include_min:
+                padding = (
+                    ".0" * (3 - version.precision) if version.precision < 3 else ""
+                )
+                part = f'python_full_version > "{version}{padding}"'
+            else:
+                part = f'{min_name} {op} "{version}"'
 
-                text += f' and {max_name} {op} "{version}"'
-
-                return text
-        elif constraint.max is not None:
-            op = "<="
-            if not constraint.include_max:
-                op = "<"
+            parts.append(part)
 
+        if constraint.max is not None:
+            op = "<=" if constraint.include_max else "<"
             version = constraint.max
-        else:
-            return ""
+            if max_name == "python_version" and version.precision >= 3:
+                max_name = "python_full_version"
 
-        if name == "python_version" and version.precision >= 3:
-            name = "python_full_version"
+            if name == "python_version" and constraint.include_max:
+                padding = (
+                    ".0" * (3 - version.precision) if version.precision < 3 else ""
+                )
+                part = f'python_full_version <= "{version}{padding}"'
+            else:
+                part = f'{max_name} {op} "{version}"'
+
+            parts.append(part)
 
-        marker = f'{name} {op} "{version}"'
+        marker = " and ".join(parts)
 
     return marker
 

tests/packages/test_package.py

@@ -533,15 +533,15 @@ def test_package_pep592_yanked(
     assert package.yanked_reason == expected_yanked_reason
 
 
-def test_python_versions_are_normalized() -> None:
+def test_python_versions_are_made_precise() -> None:
     package = Package("foo", "1.2.3")
     package.python_versions = ">3.6,<=3.10"
 
     assert (
         str(package.python_marker)
-        == 'python_version > "3.6" and python_version <= "3.10"'
+        == 'python_full_version > "3.6.0" and python_full_version <= "3.10.0"'
     )
-    assert str(package.python_constraint) == ">=3.7,<3.11"
+    assert str(package.python_constraint) == ">3.6,<=3.10"
 
 
 def test_cannot_update_package_version() -> None: