Don't call frame.f_locals multiple times when assigning locals after …

…evaluation. Fixes #915

src/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_vars.py

@@ -377,13 +377,17 @@ def _update_globals_and_locals(updated_globals, initial_globals, frame):
     # Still, the approach to have a single namespace was chosen because it was the only
     # one that enabled creating and using variables during the same evaluation.
     assert updated_globals is not None
-    changed = False
+    f_locals = None
     for key, val in updated_globals.items():
         if initial_globals.get(key) is not val:
-            changed = True
-            frame.f_locals[key] = val
+            if f_locals is None:
+                # Note: we call f_locals only once because each time
+                # we call it the values may be reset.
+                f_locals = frame.f_locals
 
-    if changed:
+            f_locals[key] = val
+
+    if f_locals is not None:
         pydevd_save_locals.save_locals(frame)
 
 

src/debugpy/_vendored/pydevd/tests_python/test_evaluate_expression.py

@@ -9,6 +9,8 @@
 
 
 def obtain_frame():
+    A = 1
+    B = 2
     yield sys._getframe()
 
 
@@ -116,3 +118,15 @@ def check(frame):
     assert 'email' in sys._getframe().f_globals
     del sys._getframe().f_globals['email']
     assert 'email' not in sys._getframe().f_globals
+
+
+def test_evaluate_expression_5(disable_critical_log):
+    from _pydevd_bundle.pydevd_vars import evaluate_expression
+
+    def check(frame):
+        eval_txt = 'A, B = 5, 6'
+        evaluate_expression(None, frame, eval_txt, is_exec=True)
+        assert frame.f_locals['A'] == 5
+        assert frame.f_locals['B'] == 6
+
+    check(next(iter(obtain_frame())))