gh-143504: Expose CELL status of a symbol in symtable

Lib/symtable.py

@@ -184,6 +184,7 @@ class Function(SymbolTable):
     __frees = None
     __globals = None
     __nonlocals = None
+    __cells = None
 
     def __idents_matching(self, test_func):
         return tuple(ident for ident in self.get_identifiers()
@@ -229,6 +230,14 @@ def get_frees(self):
             self.__frees = self.__idents_matching(is_free)
         return self.__frees
 
+    def get_cells(self):
+        """Return a tuple of cells in the function."""
+        if self.__cells is None:
+            is_cell = lambda x: _get_scope(x) == CELL
+            self.__cells = self.__idents_matching(is_cell)
+        return self.__cells
+
+
 
 class Class(SymbolTable):
 
@@ -342,6 +351,10 @@ def is_free(self):
         """
         return bool(self.__scope == FREE)
 
+    def is_cell(self):
+        """Return *True* if the symbol is a cell variable."""
+        return bool(self.__scope == CELL)
+
     def is_free_class(self):
         """Return *True* if a class-scoped symbol is free from
         the perspective of a method."""

Lib/test/test_symtable.py

@@ -611,6 +611,22 @@ def test_filter_syntax_warnings_by_module(self):
             self.assertEqual(wm.filename, filename)
             self.assertIs(wm.category, SyntaxWarning)
 
+    def test_cells(self):
+        #test for addition of is_cell() and get_cells()
+        #see https://github.com/python/cpython/issues/143504
+        code="""def outer():
+                    x=1
+                    def inner():
+                        return x"""
+
+        top=symtable.symtable(code,"?","exec")
+        outer=top.get_children()[0]
+
+        self.assertIn("x",outer.get_cells())
+
+        self.assertTrue(outer.lookup("x").is_cell())
+        self.assertFalse(outer.lookup("inner").is_cell())
+
 
 class ComprehensionTests(unittest.TestCase):
     def get_identifiers_recursive(self, st, res):