markers: add new method to reduce a marker by a Python constraint

That is useful for removing redundant information from markers.
For example, if the project's Python constraint is `>=3.9`,
a dependency's marker like `python_version >= 3.7` carries the
same information as an `AnyMarker` for this project.
(The dependency is required for all supported Python versions.)

Author: radoering

src/poetry/core/version/markers.py

@@ -20,6 +20,7 @@
 from poetry.core.constraints.generic import MultiConstraint
 from poetry.core.constraints.generic import UnionConstraint
 from poetry.core.constraints.version import VersionConstraint
+from poetry.core.constraints.version import VersionUnion
 from poetry.core.constraints.version.exceptions import ParseConstraintError
 from poetry.core.version.grammars import GRAMMAR_PEP_508_MARKERS
 from poetry.core.version.parser import Parser
@@ -107,6 +108,12 @@ def exclude(self, marker_name: str) -> BaseMarker:
     def only(self, *marker_names: str) -> BaseMarker:
         raise NotImplementedError
 
+    @abstractmethod
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        raise NotImplementedError
+
     @abstractmethod
     def invert(self) -> BaseMarker:
         raise NotImplementedError
@@ -145,6 +152,11 @@ def exclude(self, marker_name: str) -> BaseMarker:
     def only(self, *marker_names: str) -> BaseMarker:
         return self
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        return self
+
     def invert(self) -> EmptyMarker:
         return EmptyMarker()
 
@@ -186,6 +198,11 @@ def exclude(self, marker_name: str) -> EmptyMarker:
     def only(self, *marker_names: str) -> BaseMarker:
         return self
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        return self
+
     def invert(self) -> AnyMarker:
         return AnyMarker()
 
@@ -283,6 +300,11 @@ def only(self, *marker_names: str) -> BaseMarker:
 
         return self
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        return self
+
     def intersect(self, other: BaseMarker) -> BaseMarker:
         if isinstance(other, SingleMarkerLike):
             merged = _merge_single_markers(self, other, MultiMarker)
@@ -395,6 +417,18 @@ def value(self) -> str:
     def _key(self) -> tuple[object, ...]:
         return self._name, self._operator, self._value
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        if self.name in PYTHON_VERSION_MARKERS:
+            assert isinstance(self._constraint, VersionConstraint)
+            if self._constraint.allows_all(python_constraint):
+                return AnyMarker()
+            elif not self._constraint.allows_any(python_constraint):
+                return EmptyMarker()
+
+        return self
+
     def invert(self) -> BaseMarker:
         if self._operator in ("===", "=="):
             operator = "!="
@@ -670,6 +704,13 @@ def exclude(self, marker_name: str) -> BaseMarker:
     def only(self, *marker_names: str) -> BaseMarker:
         return self.of(*(m.only(*marker_names) for m in self._markers))
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        return self.of(
+            *(m.reduce_by_python_constraint(python_constraint) for m in self._markers)
+        )
+
     def invert(self) -> BaseMarker:
         markers = [marker.invert() for marker in self._markers]
 
@@ -839,6 +880,31 @@ def exclude(self, marker_name: str) -> BaseMarker:
     def only(self, *marker_names: str) -> BaseMarker:
         return self.of(*(m.only(*marker_names) for m in self._markers))
 
+    def reduce_by_python_constraint(
+        self, python_constraint: VersionConstraint
+    ) -> BaseMarker:
+        from poetry.core.packages.utils.utils import get_python_constraint_from_marker
+
+        markers: Iterable[BaseMarker] = self._markers
+        if isinstance(python_constraint, VersionUnion):
+            python_only_markers = []
+            other_markers = []
+            for m in self._markers:
+                if m == m.only(*PYTHON_VERSION_MARKERS):
+                    python_only_markers.append(m)
+                else:
+                    other_markers.append(m)
+            if get_python_constraint_from_marker(
+                self.of(*python_only_markers)
+            ).allows_all(python_constraint):
+                if not other_markers:
+                    return AnyMarker()
+                markers = other_markers
+
+        return self.of(
+            *(m.reduce_by_python_constraint(python_constraint) for m in markers)
+        )
+
     def invert(self) -> BaseMarker:
         markers = [marker.invert() for marker in self._markers]
         return MultiMarker(*markers)

tests/version/test_markers.py

@@ -8,6 +8,7 @@
 
 from poetry.core.constraints.generic import UnionConstraint
 from poetry.core.constraints.generic import parse_constraint as parse_generic_constraint
+from poetry.core.constraints.version import parse_constraint as parse_version_constraint
 from poetry.core.version.markers import AnyMarker
 from poetry.core.version.markers import AtomicMarkerUnion
 from poetry.core.version.markers import EmptyMarker
@@ -1175,6 +1176,88 @@ def test_only(marker: str, only: list[str], expected: str) -> None:
     assert str(m.only(*only)) == expected
 
 
+@pytest.mark.parametrize(
+    ("marker", "constraint", "expected"),
+    [
+        ("", "~3.8", ""),
+        ("<empty>", "~3.8", "<empty>"),
+        ('sys_platform == "linux"', "~3.8", 'sys_platform == "linux"'),
+        ('python_version >= "3.8"', "~3.8", ""),
+        ('python_version > "3.8"', "~3.8", 'python_version > "3.8"'),
+        ('python_version >= "3.9"', "~3.8", "<empty>"),
+        ('python_full_version >= "3.8.0"', "~3.8", ""),
+        ('python_full_version >= "3.8.1"', "~3.8", 'python_full_version >= "3.8.1"'),
+        ('python_full_version < "3.8.0"', "~3.8", "<empty>"),
+        ('python_version >= "3.8" and python_version < "3.9"', "~3.8", ""),
+        ('python_version >= "3.7" and python_version < "4.0"', "~3.8", ""),
+        (
+            'python_full_version >= "3.8.1" and python_version < "3.9"',
+            "~3.8",
+            'python_full_version >= "3.8.1"',
+        ),
+        (
+            'python_version >= "3.8" and python_full_version < "3.8.2"',
+            "~3.8",
+            'python_full_version < "3.8.2"',
+        ),
+        (
+            'python_version >= "3.8" and sys_platform == "linux" and python_version < "3.9"',
+            "~3.8",
+            'sys_platform == "linux"',
+        ),
+        ('python_version < "3.8" or python_version >= "3.9"', "~3.9", ""),
+        (
+            'python_version < "3.8" or python_version >= "3.9"',
+            ">=3.7",
+            'python_version < "3.8" or python_version >= "3.9"',
+        ),
+        ('python_version < "3.8" or python_version >= "3.9"', "~3.7", ""),
+        (
+            'python_version < "3.8" or python_version >= "3.9"',
+            "<=3.10",
+            'python_version < "3.8" or python_version >= "3.9"',
+        ),
+        (
+            (
+                'python_version < "3.8"'
+                ' or python_version >= "3.9" and sys_platform == "linux"'
+            ),
+            "~3.9",
+            'sys_platform == "linux"',
+        ),
+        ('python_version < "3.8" or python_version >= "3.9"', "~3.7 || ~3.9", ""),
+        (
+            'python_version < "3.8" or python_version >= "3.9"',
+            "~3.6 || ~3.8",
+            'python_version < "3.8"',
+        ),
+        (
+            (
+                'python_version < "3.8" or sys_platform == "linux"'
+                ' or python_version >= "3.9"'
+            ),
+            "~3.7 || ~3.9",
+            'sys_platform == "linux"',
+        ),
+        (
+            (
+                'python_version < "3.8" or sys_platform == "linux"'
+                ' or python_version >= "3.9" or sys_platform == "win32"'
+            ),
+            "~3.7 || ~3.9",
+            'sys_platform == "linux" or sys_platform == "win32"',
+        ),
+    ],
+)
+def test_reduce_by_python_constraint(
+    marker: str, constraint: str, expected: str
+) -> None:
+    m = parse_marker(marker)
+    c = parse_version_constraint(constraint)
+
+    assert str(m.reduce_by_python_constraint(c)) == expected
+
+
 def test_union_of_a_single_marker_is_the_single_marker() -> None:
     union = MarkerUnion.of(SingleMarker("python_version", ">= 2.7"))