Make rpc callback exception more explicit and wind up to show more in…

…fos (#305)

(cherry picked from commit ecef9b9)

src/plumpy/processes.py

@@ -1020,11 +1020,37 @@ def _schedule_rpc(self, callback: Callable[..., Any], *args: Any, **kwargs: Any)
 
         async def run_callback() -> None:
             with kiwipy.capture_exceptions(kiwi_future):
-                result = callback(*args, **kwargs)
-                while asyncio.isfuture(result):
-                    result = await result
+                try:
+                    result = callback(*args, **kwargs)
+                except Exception as exc:
+                    import inspect
+                    import traceback
+
+                    # Get traceback as a string
+                    tb_str = ''.join(traceback.format_exception(type(exc), exc, exc.__traceback__))
+
+                    # Attempt to get file and line number where the callback is defined
+                    # Note: This might fail for certain built-in or dynamically generated functions.
+                    # If it fails, just skip that part.
+                    try:
+                        source_file = inspect.getfile(callback)
+                        # getsourcelines returns a tuple (list_of_source_lines, starting_line_number)
+                        _, start_line = inspect.getsourcelines(callback)
+                        callback_location = f'{source_file}:{start_line}'
+                    except Exception:
+                        callback_location = '<unknown location>'
+
+                    # Include the callback name, file/line info, and the full traceback in the message
+                    raise RuntimeError(
+                        f"Error invoking callback '{callback.__name__}' at {callback_location}.\n"
+                        f'Exception: {type(exc).__name__}: {exc}\n\n'
+                        f'Full Traceback:\n{tb_str}'
+                    ) from exc
+                else:
+                    while asyncio.isfuture(result):
+                        result = await result
 
-                kiwi_future.set_result(result)
+                    kiwi_future.set_result(result)
 
         # Schedule the task and give back a kiwi future
         asyncio.run_coroutine_threadsafe(run_callback(), self.loop)