feat(end_stream_processor): support streaming output of all configured variables in End node

- Iterate all variable selectors for all end nodes and stream if matched
- Add detailed English comments explaining each step of the logic
- This enables streaming output for multiple variables (e.g., text, text1, text2...) instead of only the first one

api/core/workflow/nodes/end/end_stream_processor.py

@@ -42,23 +42,26 @@ class EndStreamProcessor(StreamProcessor):
                     yield event
                     continue
 
-                if event.route_node_state.node_id in self.current_stream_chunk_generating_node_ids:
-                    stream_out_end_node_ids = self.current_stream_chunk_generating_node_ids[
-                        event.route_node_state.node_id
-                    ]
-                else:
-                    stream_out_end_node_ids = self._get_stream_out_end_node_ids(event)
-                    self.current_stream_chunk_generating_node_ids[event.route_node_state.node_id] = (
-                        stream_out_end_node_ids
-                    )
-
-                if stream_out_end_node_ids:
-                    if self.has_output and event.node_id not in self.output_node_ids:
-                        event.chunk_content = "\n" + event.chunk_content
-
-                    self.output_node_ids.add(event.node_id)
-                    self.has_output = True
-                    yield event
+                # Iterate all variable selectors for all end nodes; stream if matched
+                matched = False  # Flag to indicate if a match is found
+                for end_node_id, value_selectors_list in self.end_stream_param.end_stream_variable_selector_mapping.items():
+                    # Loop through all variable selectors configured for the current end node
+                    for value_selector in value_selectors_list:
+                        # Check if the current event's from_variable_selector matches the configured selector
+                        if event.from_variable_selector == value_selector:
+                            # If there was previous output and this node hasn't output yet, prepend a newline
+                            if self.has_output and event.node_id not in self.output_node_ids:
+                                event.chunk_content = "\n" + event.chunk_content
+                            # Mark this node as having output to avoid duplicate newlines
+                            self.output_node_ids.add(event.node_id)
+                            # Set the flag indicating output has occurred
+                            self.has_output = True
+                            # Stream the current event
+                            yield event
+                            matched = True  # Set matched flag to break out of loops
+                            break  # Exit inner loop after match
+                    if matched:
+                        break  # Exit outer loop after match
             elif isinstance(event, NodeRunSucceededEvent):
                 yield event
                 if event.route_node_state.node_id in self.current_stream_chunk_generating_node_ids: