Fix slow perf in 0.4.2+

libcst/metadata/scope_provider.py

@@ -406,16 +406,18 @@ class Scope(abc.ABC):
     #: Refers to the GlobalScope.
     globals: "GlobalScope"
     _assignments: MutableMapping[str, Set[BaseAssignment]]
-    _accesses: MutableMapping[str, Set[Access]]
     _assignment_count: int
+    __accesses_by_name: MutableMapping[str, Set[Access]]
+    __accesses_by_node: MutableMapping[cst.CSTNode, Set[Access]]
 
     def __init__(self, parent: "Scope") -> None:
         super().__init__()
         self.parent = parent
         self.globals = parent.globals
         self._assignments = defaultdict(set)
-        self._accesses = defaultdict(set)
         self._assignment_count = 0
+        self.__accesses_by_name = defaultdict(set)
+        self.__accesses_by_node = defaultdict(set)
 
     def record_assignment(self, name: str, node: cst.CSTNode) -> None:
         target = self._find_assignment_target(name)
@@ -446,7 +448,8 @@ def _find_assignment_target_parent(self, name: str) -> "Scope":
         return self
 
     def record_access(self, name: str, access: Access) -> None:
-        self._accesses[name].add(access)
+        self.__accesses_by_name[name].add(access)
+        self.__accesses_by_node[access.node].add(access)
 
     def _getitem_from_self_or_parent(self, name: str) -> Set[BaseAssignment]:
         """Overridden by ClassScope to hide it's assignments from child scopes."""
@@ -545,12 +548,9 @@ def f(self) -> "c":
         """
 
         # if this node is an access we know the assignment and we can use that name
-        node_accesses = {
-            access
-            for all_accesses in self._accesses.values()
-            for access in all_accesses
-            if access.node == node
-        }
+        node_accesses = (
+            self.__accesses_by_node.get(node) if isinstance(node, cst.CSTNode) else None
+        )
         if node_accesses:
             return {
                 qname
@@ -589,7 +589,7 @@ def assignments(self) -> Assignments:
     @property
     def accesses(self) -> Accesses:
         """Return an :class:`~libcst.metadata.Accesses` contains all accesses in current scope."""
-        return Accesses(self._accesses)
+        return Accesses(self.__accesses_by_name)
 
 
 class BuiltinScope(Scope):

libcst/metadata/tests/test_scope_provider.py

@@ -1445,35 +1445,33 @@ def test_keyword_arg_in_call(self) -> None:
 
     def test_global_contains_is_read_only(self) -> None:
         gscope = GlobalScope()
-        before_assignments = list(gscope._assignments.items())
-        before_accesses = list(gscope._accesses.items())
+        before_assignments = list(gscope.assignments)
+        before_accesses = list(gscope.accesses)
         self.assertFalse("doesnt_exist" in gscope)
-        self.assertEqual(list(gscope._accesses.items()), before_accesses)
-        self.assertEqual(list(gscope._assignments.items()), before_assignments)
+        self.assertEqual(list(gscope.accesses), before_accesses)
+        self.assertEqual(list(gscope.assignments), before_assignments)
 
     def test_contains_is_read_only(self) -> None:
         for s in [LocalScope, FunctionScope, ClassScope, ComprehensionScope]:
             with self.subTest(scope=s):
                 gscope = GlobalScope()
                 scope = s(parent=gscope, node=cst.Name("lol"))
-                before_assignments = list(scope._assignments.items())
-                before_accesses = list(scope._accesses.items())
+                before_assignments = list(scope.assignments)
+                before_accesses = list(scope.accesses)
                 before_overwrites = list(scope._scope_overwrites.items())
-                before_parent_assignments = list(scope.parent._assignments.items())
-                before_parent_accesses = list(scope.parent._accesses.items())
+                before_parent_assignments = list(scope.parent.assignments)
+                before_parent_accesses = list(scope.parent.accesses)
 
                 self.assertFalse("doesnt_exist" in scope)
-                self.assertEqual(list(scope._accesses.items()), before_accesses)
-                self.assertEqual(list(scope._assignments.items()), before_assignments)
+                self.assertEqual(list(scope.accesses), before_accesses)
+                self.assertEqual(list(scope.assignments), before_assignments)
                 self.assertEqual(
                     list(scope._scope_overwrites.items()), before_overwrites
                 )
                 self.assertEqual(
-                    list(scope.parent._assignments.items()), before_parent_assignments
-                )
-                self.assertEqual(
-                    list(scope.parent._accesses.items()), before_parent_accesses
+                    list(scope.parent.assignments), before_parent_assignments
                 )
+                self.assertEqual(list(scope.parent.accesses), before_parent_accesses)
 
     def test_attribute_of_function_call(self) -> None:
         get_scope_metadata_provider("foo().bar")
@@ -1496,11 +1494,11 @@ def test_get_qualified_names_for_is_read_only(self) -> None:
         )
         a = m.body[0]
         scope = scopes[a]
-        assignments_len_before = len(scope._assignments)
-        accesses_len_before = len(scope._accesses)
+        assignments_before = list(scope.assignments)
+        accesses_before = list(scope.accesses)
         scope.get_qualified_names_for("doesnt_exist")
-        self.assertEqual(len(scope._assignments), assignments_len_before)
-        self.assertEqual(len(scope._accesses), accesses_len_before)
+        self.assertEqual(list(scope.assignments), assignments_before)
+        self.assertEqual(list(scope.accesses), accesses_before)
 
     def test_gen_dotted_names(self) -> None:
         names = {name for name, node in _gen_dotted_names(cst.Name(value="a"))}