Prevent logged warning when span is double-ended at interpreter shutdown (#704)

Author: alexmojaki

logfire/_internal/config.py

@@ -944,8 +944,15 @@ def _exit_open_spans():  # type: ignore[reportUnusedFunction]  # pragma: no cove
                 # OTEL registers its own atexit callback in the tracer/meter providers to shut them down.
                 # Registering this callback here after the OTEL one means that this runs first.
                 # Otherwise OTEL would log an error "Already shutdown, dropping span."
+                # The reason that spans may be lingering open is that they're in suspended generator frames.
+                # Apart from here, they will be ended when the generator is garbage collected
+                # as the interpreter shuts down, but that's too late.
                 for span in list(OPEN_SPANS):
+                    # TODO maybe we should be recording something about what happened here?
                     span.end()
+                    # Interpreter shutdown may trigger another call to .end(),
+                    # which would log a warning "Calling end() on an ended span."
+                    span.end = lambda *_, **__: None  # type: ignore
 
             self._initialized = True