Explain why function is called twice

Author: wch

shiny/express/_run.py

@@ -99,6 +99,11 @@ def set_result(x: object):
                 var_context,
             )
 
+    # When we called the function to get the top level recall context manager, we didn't
+    # store the result in a variable and re-use that variable here. That is intentional,
+    # because during the evaluation of the app code,
+    # replace_top_level_recall_context_manager() may have been called, which swaps
+    # out the context manager, and it's the new one that we need to exit here.
     get_top_level_recall_context_manager().__exit__(None, None, None)
 
     # If we're running as an Express app but there's also a top-level item named app