fix: make Requirements/Markers pickle-safe (#1171)

* fix: make Requirements/Markers pickle-safe

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* tests: restore full coverage

Assisted-by: OpenCode:Qwen3.6-27B
Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* fix: address copilot review

Assisted-by: Copilot:Kimi-K2.6
Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* docs: fix mentioned version number

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

---------

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

Author: henryiii

src/packaging/_parser.py

@@ -27,6 +27,34 @@ def __repr__(self) -> str:
     def serialize(self) -> str:
         raise NotImplementedError
 
+    def __getstate__(self) -> str:
+        # Return just the value string for compactness and stability.
+        return self.value
+
+    def _restore_value(self, value: object) -> None:
+        if not isinstance(value, str):
+            raise TypeError(
+                f"Cannot restore {self.__class__.__name__} value from {value!r}"
+            )
+        self.value = value
+
+    def __setstate__(self, state: object) -> None:
+        if isinstance(state, str):
+            # New format (26.2+): just the value string.
+            self._restore_value(state)
+            return
+        if isinstance(state, tuple) and len(state) == 2:
+            # Old format (packaging <= 26.0, __slots__): (None, {slot: value}).
+            _, slot_dict = state
+            if isinstance(slot_dict, dict) and "value" in slot_dict:
+                self._restore_value(slot_dict["value"])
+                return
+        if isinstance(state, dict) and "value" in state:
+            # Old format (packaging <= 25.0, no __slots__): plain __dict__.
+            self._restore_value(state["value"])
+            return
+        raise TypeError(f"Cannot restore {self.__class__.__name__} from {state!r}")
+
 
 class Variable(Node):
     __slots__ = ()

src/packaging/markers.py

@@ -381,6 +381,35 @@ def __eq__(self, other: object) -> bool:
 
         return str(self) == str(other)
 
+    def __getstate__(self) -> str:
+        # Return the marker expression string for compactness and stability.
+        # Internal Node objects are excluded; the string is re-parsed on load.
+        return str(self)
+
+    def __setstate__(self, state: object) -> None:
+        if isinstance(state, str):
+            # New format (26.2+): just the marker expression string.
+            try:
+                self._markers = _normalize_extra_values(_parse_marker(state))
+            except ParserSyntaxError as exc:
+                raise TypeError(f"Cannot restore Marker from {state!r}") from exc
+            return
+        if isinstance(state, dict) and "_markers" in state:
+            # Old format (packaging <= 26.1, no __slots__): plain __dict__.
+            markers = state["_markers"]
+            if isinstance(markers, list):
+                self._markers = markers
+                return
+        if isinstance(state, tuple) and len(state) == 2:
+            # Old format (packaging <= 26.1, __slots__): (None, {slot: value}).
+            _, slot_dict = state
+            if isinstance(slot_dict, dict) and "_markers" in slot_dict:
+                markers = slot_dict["_markers"]
+                if isinstance(markers, list):
+                    self._markers = markers
+                    return
+        raise TypeError(f"Cannot restore Marker from {state!r}")
+
     def __and__(self, other: Marker) -> Marker:
         if not isinstance(other, Marker):
             return NotImplemented

src/packaging/requirements.py

@@ -73,6 +73,30 @@ def _iter_parts(self, name: str) -> Iterator[str]:
         if self.marker:
             yield f"; {self.marker}"
 
+    def __getstate__(self) -> str:
+        # Return the requirement string for compactness and stability.
+        # Re-parsed on load to reconstruct all fields.
+        return str(self)
+
+    def __setstate__(self, state: object) -> None:
+        if isinstance(state, str):
+            # New format (26.2+): just the requirement string.
+            try:
+                tmp = Requirement(state)
+            except InvalidRequirement as exc:
+                raise TypeError(f"Cannot restore Requirement from {state!r}") from exc
+            self.name = tmp.name
+            self.url = tmp.url
+            self.extras = tmp.extras
+            self.specifier = tmp.specifier
+            self.marker = tmp.marker
+            return
+        if isinstance(state, dict):
+            # Old format (packaging <= 26.1, no __slots__): plain __dict__.
+            self.__dict__.update(state)
+            return
+        raise TypeError(f"Cannot restore Requirement from {state!r}")
+
     def __str__(self) -> str:
         return "".join(self._iter_parts(self.name))
 

tests/test_markers.py

@@ -6,14 +6,15 @@
 
 import itertools
 import os
+import pickle
 import platform
 import sys
 from typing import Any, NamedTuple, cast
 from unittest import mock
 
 import pytest
 
-from packaging._parser import Node
+from packaging._parser import Node, Op, Value, Variable
 from packaging.markers import (
     InvalidMarker,
     Marker,
@@ -564,3 +565,157 @@ def test_evaluation_of_combined_markers() -> None:
         & Marker('platform_system == "Linux"')
     )
     assert m.evaluate(env) is True
+
+
+@pytest.mark.parametrize(
+    "marker_str",
+    [
+        'python_version >= "3.8"',
+        'python_version >= "3.8" and os_name == "posix"',
+        'python_version >= "3.8" or platform_system == "Windows"',
+        'extra == "security"',
+    ],
+)
+def test_pickle_marker_roundtrip(marker_str: str) -> None:
+    # Make sure equality and str() work between a pickle/unpickle round trip.
+    m = Marker(marker_str)
+    loaded = pickle.loads(pickle.dumps(m))
+    assert loaded == m
+    assert str(loaded) == str(m)
+
+
+def test_pickle_marker_setstate_rejects_invalid_state() -> None:
+    # Cover the TypeError branches in __setstate__ for invalid input.
+    m = Marker.__new__(Marker)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m.__setstate__(12345)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m.__setstate__((1, 2, 3))  # Wrong tuple length
+
+
+# Pickle bytes generated with packaging==26.1, Python 3.13.1, pickle protocol 2.
+# Format: __slots__ (no __getstate__), state is (None, {slot: value}).
+_PACKAGING_26_1_PICKLE_MARKER_PYTHON_VERSION_GE_3_8 = (
+    b"\x80\x02cpackaging.markers\nMarker\nq\x00)\x81q\x01N}q\x02X\x08\x00"
+    b"\x00\x00_markersq\x03]q\x04cpackaging._parser\nVariable\nq\x05)\x81"
+    b"q\x06N}q\x07X\x05\x00\x00\x00valueq\x08X\x0e\x00\x00\x00python_vers"
+    b"ionq\ts\x86q\nbcpackaging._parser\nOp\nq\x0b)\x81q\x0cN}q\rh\x08X\x02"
+    b"\x00\x00\x00>=q\x0es\x86q\x0fbcpackaging._parser\nValue\nq\x10)\x81q"
+    b"\x11N}q\x12h\x08X\x03\x00\x00\x003.8q\x13s\x86q\x14b\x87q\x15as\x86"
+    b"q\x16b."
+)
+
+
+# Pickle bytes generated with packaging==26.0, Python 3.13.1, pickle protocol 2.
+# Format: __slots__ (no __getstate__), state is plain __dict__.
+_PACKAGING_26_0_PICKLE_MARKER_PYTHON_VERSION_GE_3_8 = (
+    b"\x80\x02cpackaging.markers\nMarker\nq\x00)\x81q\x01}q\x02X\x08\x00\x00"
+    b"\x00_markersq\x03]q\x04cpackaging._parser\nVariable\nq\x05)\x81q\x06N}"
+    b"q\x07X\x05\x00\x00\x00valueq\x08X\x0e\x00\x00\x00python_versionq\ts\x86"
+    b"q\nbcpackaging._parser\nOp\nq\x0b)\x81q\x0cN}q\rh\x08X\x02\x00\x00"
+    b"\x00>=q\x0es\x86q\x0fbcpackaging._parser\nValue\nq\x10)\x81q\x11N}q\x12"
+    b"h\x08X\x03\x00\x00\x003.8q\x13s\x86q\x14b\x87q\x15asb."
+)
+
+# Format: __slots__ with Node objects using __dict__ format (packaging <= 25.0).
+# Now loadable because Node classes have __getstate__/__setstate__.
+_PACKAGING_25_0_PICKLE_MARKER_PYTHON_VERSION_GE_3_8 = (
+    b"\x80\x02cpackaging.markers\nMarker\nq\x00)\x81q\x01}q\x02X\x08\x00\x00"
+    b"\x00_markersq\x03]q\x04cpackaging._parser\nVariable\nq\x05)\x81q\x06}q\x07"
+    b"X\x05\x00\x00\x00valueq\x08X\x0e\x00\x00\x00python_versionq\tsbcpackaging"
+    b"._parser\nOp\nq\n)\x81q\x0b}q\x0ch\x08X\x02\x00\x00\x00>=q\rsbcpackaging"
+    b"._parser\nValue\nq\x0e)\x81q\x0f}q\x10h\x08X\x03\x00\x00\x003.8q\x11sb\x87"
+    b"q\x12asb."
+)
+
+
+def test_pickle_marker_old_format_loads() -> None:
+    # Verify that Marker pickles created with packaging <= 26.1 (__slots__,
+    # no __getstate__) can be loaded and produce correct Marker objects.
+    m = pickle.loads(_PACKAGING_26_1_PICKLE_MARKER_PYTHON_VERSION_GE_3_8)
+    assert isinstance(m, Marker)
+    assert str(m) == 'python_version >= "3.8"'
+    assert m == Marker('python_version >= "3.8"')
+
+
+def test_pickle_marker_26_0_format_loads() -> None:
+    # Verify that Marker pickles created with packaging 26.0 (plain __dict__)
+    # can be loaded and produce correct Marker objects.
+    m = pickle.loads(_PACKAGING_26_0_PICKLE_MARKER_PYTHON_VERSION_GE_3_8)
+    assert isinstance(m, Marker)
+    assert str(m) == 'python_version >= "3.8"'
+    assert m == Marker('python_version >= "3.8"')
+
+
+def test_pickle_marker_25_0_format_loads() -> None:
+    # Verify that Marker pickles created with packaging 25.0 (with Node __dict__)
+    # can now be loaded thanks to __getstate__/__setstate__ in Node classes.
+    m = pickle.loads(_PACKAGING_25_0_PICKLE_MARKER_PYTHON_VERSION_GE_3_8)
+    assert isinstance(m, Marker)
+    assert str(m) == 'python_version >= "3.8"'
+    assert m == Marker('python_version >= "3.8"')
+
+
+def test_pickle_node_roundtrip() -> None:
+    # Cover Node.__getstate__ and Node.__setstate__ with the new string format.
+    for node in (Variable("python_version"), Value("3.8"), Op(">=")):
+        loaded = pickle.loads(pickle.dumps(node))
+        assert loaded.value == node.value
+        assert str(loaded) == str(node)
+
+
+def test_pickle_node_setstate_rejects_invalid_state() -> None:
+    # Cover the TypeError branch in Node.__setstate__ for invalid input.
+    node = Variable.__new__(Variable)
+    with pytest.raises(TypeError, match="Cannot restore Variable"):
+        node.__setstate__(12345)
+
+    node2 = Variable.__new__(Variable)
+    with pytest.raises(TypeError, match="Cannot restore Variable"):
+        node2.__setstate__((1, 2, 3))  # Wrong tuple length
+
+    # Cover the legacy tuple branch where slot_dict doesn't have "value".
+    node3 = Variable.__new__(Variable)
+    with pytest.raises(TypeError, match="Cannot restore Variable"):
+        node3.__setstate__((None, {"wrong_key": "foo"}))
+
+    # Cover the legacy tuple branch where slot_dict has "value" but it's not a str.
+    node4 = Variable.__new__(Variable)
+    with pytest.raises(TypeError, match="Cannot restore Variable value from 123"):
+        node4.__setstate__((None, {"value": 123}))
+
+    # Cover the legacy dict branch where "value" exists but it's not a str.
+    node5 = Value.__new__(Value)
+    with pytest.raises(TypeError, match="Cannot restore Value value from 456"):
+        node5.__setstate__({"value": 456})
+
+    # Cover the legacy dict branch on Op (different subclass to ensure coverage).
+    node6 = Op.__new__(Op)
+    with pytest.raises(TypeError, match="Cannot restore Op value from 789"):
+        node6.__setstate__({"value": 789})
+
+
+def test_pickle_marker_setstate_legacy_slot_dict_without_markers_key() -> None:
+    # Cover Marker.__setstate__ legacy tuple branch where slot_dict has no "_markers".
+    m = Marker.__new__(Marker)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m.__setstate__((None, {"other_key": "value"}))
+
+
+def test_pickle_marker_setstate_rejects_invalid_markers_type() -> None:
+    # Cover the dict branch where "_markers" exists but is not a list.
+    m1 = Marker.__new__(Marker)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m1.__setstate__({"_markers": "not a list"})
+
+    # Cover the tuple branch where "_markers" exists but is not a list.
+    m2 = Marker.__new__(Marker)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m2.__setstate__((None, {"_markers": "not a list"}))
+
+
+def test_pickle_marker_setstate_rejects_invalid_marker_string() -> None:
+    # Cover the string branch where parsing raises ParserSyntaxError.
+    m = Marker.__new__(Marker)
+    with pytest.raises(TypeError, match="Cannot restore Marker"):
+        m.__setstate__("this is not a valid marker")