use WeakKeyDictionary instead of lru cache

hypothesis-python/src/hypothesis/internal/reflection.py

@@ -29,6 +29,7 @@
 from types import ModuleType
 from typing import TYPE_CHECKING, Any, Callable
 from unittest.mock import _patch as PatchType
+from weakref import WeakKeyDictionary
 
 from hypothesis.errors import HypothesisWarning
 from hypothesis.internal.compat import PYPY, is_typed_named_tuple
@@ -39,6 +40,7 @@
     from hypothesis.strategies._internal.strategies import T
 
 READTHEDOCS = os.environ.get("READTHEDOCS", None) == "True"
+PRETTY_FUNCTION_CACHE = WeakKeyDictionary()
 
 
 def is_mock(obj):
@@ -440,11 +442,7 @@ def extract_lambda_source(f):
     return source.strip()
 
 
-def get_pretty_function_description(f):
-    if isinstance(f, partial):
-        return pretty(f)
-    if not hasattr(f, "__name__"):
-        return repr(f)
+def _pretty_function_description(f):
     name = f.__name__
     if name == "<lambda>":
         return extract_lambda_source(f)
@@ -462,6 +460,23 @@ def get_pretty_function_description(f):
     return name
 
 
+def get_pretty_function_description(f):
+    # handle non-hashable cases before the cache
+    if isinstance(f, partial):
+        return pretty(f)
+    if not hasattr(f, "__name__"):
+        return repr(f)
+
+    try:
+        return PRETTY_FUNCTION_CACHE[f]
+    except KeyError:
+        pass
+
+    description = _pretty_function_description(f)
+    PRETTY_FUNCTION_CACHE[f] = description
+    return description
+
+
 def nicerepr(v):
     if inspect.isfunction(v):
         return get_pretty_function_description(v)
@@ -493,7 +508,7 @@ def repr_call(f, args, kwargs, *, reorder=True):
     if repr_len > 30000:
         warnings.warn(
             "Generating overly large repr. This is an expensive operation, and with "
-            f"a length of {repr_len//1000} kB is is unlikely to be useful. Use -Wignore "
+            f"a length of {repr_len//1000} kB is unlikely to be useful. Use -Wignore "
             "to ignore the warning, or -Werror to get a traceback.",
             HypothesisWarning,
             stacklevel=2,