Handle PreparedScanEvent as 'on_scan_started'

bliss/data/scan.py

@@ -115,6 +115,16 @@ class ScansObserver:
         """
         pass
 
+    def on_scan_started(self, scan_db_name: str, scan_info: Dict):
+        """
+        Called upon scan started (the devices was prepared).
+
+        Arguments:
+            scan_db_name: Identifier of the scan
+            scan_info: Dictionary containing scan metadata
+        """
+        pass
+
     def on_child_created(self, scan_db_name: str, node):
         """
         Called upon scan child creation (e.g. channel node)
@@ -403,6 +413,16 @@ class ScansWatcher:
                                     )
                                 except Exception:
                                     sys.excepthook(*sys.exc_info())
+                elif event_type == EventType.PREPARED_SCAN:
+                    node_type = node.type
+                    if self._watch_scan_group or node_type == "scan":
+                        db_name = node.db_name
+                        if db_name in self._running_scans:
+                            scan_info = node.info.get_all()
+                            try:
+                                observer.on_scan_started(db_name, scan_info)
+                            except Exception:
+                                sys.excepthook(*sys.exc_info())
                 elif event_type == EventType.END_SCAN:
                     node_type = node.type
                     if self._watch_scan_group or node_type == "scan":

tests/scans/test_data_watch.py

@@ -466,7 +466,9 @@ def test_scan_observer(session, diode_acq_device_factory, mocker):
         gevent.sleep(0.5)
         session_watcher.kill()
 
+    # TODO check the order of the received events
     observer.on_scan_created.assert_called_once()
+    observer.on_scan_started.assert_called_once()
     observer.on_scan_finished.assert_called_once()
     call = observer.on_scan_created.call_args_list[0]
     scan_info = call[0][1]