Implement None-cache as LRU

Constrain size of cache to avoid endless growth edge case.

Author: mdeck

Lib/inspect.py

@@ -974,7 +974,22 @@ def getabsfile(object, _filename=None):
 
 modulesbyfile = {}
 _filesbymodname = {}
-_moduleless = defaultdict(set)
+_moduleless = OrderedDict()
+_NONE_CACHE_SIZE = 1024
+
+def _is_cached_none(code):
+    if hashcode := _moduleless.get(id(code)):
+        if hash(code) == hashcode:
+            _moduleless.move_to_end(id(code), last=True)
+            return True
+    return False
+
+def _cache_none(code):
+    if not code:
+        return
+    _moduleless[id(code)] = hash(code)
+    if len(_moduleless) > _NONE_CACHE_SIZE:
+        _moduleless.popitem(last=False)
 
 def getmodule(object, _filename=None):
     """Return the module an object was defined in, or None if not found."""
@@ -987,19 +1002,16 @@ def getmodule(object, _filename=None):
         return sys.modules.get(modulesbyfile[_filename])
     # Check for moduleless objects
     code = _getcode(object)
-    if hashes := _moduleless.get(id(code)):
-        if hash(code) in hashes:
-            return None
+    if _is_cached_none(code):
+        return None
     # Try the cache again with the absolute file name
     try:
         file = getabsfile(object, _filename)
     except (TypeError, FileNotFoundError):
-        if code:
-            _moduleless[id(code)].add(hash(code))
+        _cache_none(code)
+        return None
+    if _is_cached_none(code):
         return None
-    if hashes := _moduleless.get(id(code)):
-        if hash(code) in hashes:
-            return None
     if file in modulesbyfile:
         return sys.modules.get(modulesbyfile[file])
     _update_module_file_name_cache()
@@ -1008,8 +1020,7 @@ def getmodule(object, _filename=None):
     # Check the main module
     main = sys.modules['__main__']
     if not hasattr(object, '__name__'):
-        if code:
-            _moduleless[id(code)].add(hash(code))
+        _cache_none(code)
         return None
     if hasattr(main, object.__name__):
         mainobject = getattr(main, object.__name__)
@@ -1021,8 +1032,7 @@ def getmodule(object, _filename=None):
         builtinobject = getattr(builtin, object.__name__)
         if builtinobject is object:
             return builtin
-    if code:
-        _moduleless[id(code)].add(hash(code))
+    _cache_none(code)
     return None
 
 def _update_module_file_name_cache():