Built in pickle remapper

permacache/__init__.py

@@ -2,4 +2,4 @@
 from .cache_miss_error import CacheMissError, error_on_miss_global
 from .dict_function import drop_if, drop_if_equal
 from .hash import stable_hash, stringify
-from .swap_unpickler import swap_unpickler_context_manager
+from .swap_unpickler import renamed_symbol_unpickler, swap_unpickler_context_manager

permacache/swap_unpickler.py

@@ -1,5 +1,6 @@
 import pickle
 import shelve
+from typing import Dict, Tuple, Union
 
 
 class swap_unpickler_context_manager:
@@ -18,3 +19,39 @@ def __exit__(self, typ, value, traceback):
             self._previous_unpickler = None
         else:
             shelve.Unpickler = pickle.Unpickler
+
+
+def renamed_symbol_unpickler(
+    symbol_rename_map: Dict[Tuple[str, str], Union[Tuple[str, str], type]]
+) -> type:
+    """
+    Returns an unpickler class that renames symbols as specified in
+    the symbol_rename_map dictionaries.
+
+    :param symbol_rename_map: A dictionary mapping (module, name) pairs to
+        (new_module, new_name) pairs. Can also map to a type, in which case
+        we convert the type to a (module, name) pair.
+    """
+
+    symbol_rename_map_string = {}
+    for (module, name), new_symbol in symbol_rename_map.items():
+        if isinstance(new_symbol, type):
+            new_symbol = (new_symbol.__module__, new_symbol.__name__)
+        assert (
+            isinstance(new_symbol, tuple)
+            and len(new_symbol) == 2
+            and all(isinstance(x, str) for x in new_symbol)
+        ), f"Invalid new symbol: {new_symbol}"
+        symbol_rename_map_string[(module, name)] = new_symbol
+
+    class RenamedSymbolUnpickler(pickle.Unpickler):
+        def find_class(self, module, name):
+            if (module, name) in symbol_rename_map_string:
+                module, name = symbol_rename_map_string[(module, name)]
+            try:
+                return super().find_class(module, name)
+            except:
+                print("Could not find", (module, name))
+                raise
+
+    return RenamedSymbolUnpickler

setup.py

@@ -5,7 +5,7 @@
 
 setuptools.setup(
     name="permacache",
-    version="3.7.3",
+    version="3.8.0",
     author="Kavi Gupta",
     author_email="[email protected]",
     description="Permanant cache.",

tests/test_cache.py

@@ -2,6 +2,14 @@
 import unittest
 
 from permacache import cache
+from permacache.swap_unpickler import (
+    renamed_symbol_unpickler,
+    swap_unpickler_context_manager,
+)
+
+from .test_module.a import X as a_X
+from .test_module.a import Y as a_Y
+from .test_module.b import X as b_X
 
 
 # pylint: disable=keyword-arg-before-vararg
@@ -35,3 +43,80 @@ def test_basic(self):
         self.assertEqual(fn.counter, 2)
         self.assertEqual(self.f(3, 2, 1, 0, -1), (3, 2, 1, (0, -1)))
         self.assertEqual(fn.counter, 3)
+
+
+def g(x):
+    g.counter += 1
+    return a_X(x)
+
+
+class PermacacheRemappingTest(unittest.TestCase):
+    def setUp(self):
+        # we clean this up in tearDown
+        # pylint: disable=consider-using-with
+        self.dir = tempfile.TemporaryDirectory()
+        cache.CACHE = self.dir.name
+        g.counter = 0
+        self.f = cache.permacache("g")(g)
+        self.assertIsInstance(self.f(1), a_X)
+        self.assertEqual(g.counter, 1)
+
+    def tearDown(self):
+        self.dir.__exit__(None, None, None)
+
+    def test_swap_to_b(self):
+        # populate cache
+        # swap to b
+        self.f = cache.permacache(
+            "g",
+            read_from_shelf_context_manager=swap_unpickler_context_manager(
+                renamed_symbol_unpickler(
+                    {
+                        (
+                            "tests.test_module.a",
+                            "X",
+                        ): b_X
+                    }
+                )
+            ),
+        )(g)
+        self.assertIsInstance(self.f(1), b_X)
+        self.assertEqual(g.counter, 1)
+
+    def test_swap_to_y(self):
+        # populate cache
+        # swap to y
+        self.f = cache.permacache(
+            "g",
+            read_from_shelf_context_manager=swap_unpickler_context_manager(
+                renamed_symbol_unpickler(
+                    {
+                        (
+                            "tests.test_module.a",
+                            "X",
+                        ): a_Y
+                    }
+                )
+            ),
+        )(g)
+        self.assertIsInstance(self.f(1), a_Y)
+        self.assertEqual(g.counter, 1)
+
+    def test_use_name(self):
+        # populate cache
+        # swap to y
+        self.f = cache.permacache(
+            "g",
+            read_from_shelf_context_manager=swap_unpickler_context_manager(
+                renamed_symbol_unpickler(
+                    {
+                        (
+                            "tests.test_module.a",
+                            "X",
+                        ): ("tests.test_module.a", "Y")
+                    }
+                )
+            ),
+        )(g)
+        self.assertIsInstance(self.f(1), a_Y)
+        self.assertEqual(g.counter, 1)

tests/test_module/a.py

@@ -0,0 +1,8 @@
+class X:
+    def __init__(self, x):
+        self.x = x
+
+
+class Y:
+    def __init__(self, x):
+        self.x = x

tests/test_module/b.py

@@ -0,0 +1,3 @@
+class X:
+    def __init__(self, x):
+        self.x = x