Revert PanelCallbackHandler change

examples/reference/chat/ChatFeed.ipynb

@@ -31,7 +31,7 @@
     "\n",
     "Check out the [panel-chat-examples](https://holoviz-topics.github.io/panel-chat-examples/) docs to see applicable examples related to [LangChain](https://python.langchain.com/docs/get_started/introduction), [OpenAI](https://openai.com/blog/chatgpt), [Mistral](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjZtP35yvSBAxU00wIHHerUDZAQFnoECBEQAQ&url=https%3A%2F%2Fdocs.mistral.ai%2F&usg=AOvVaw2qpx09O_zOzSksgjBKiJY_&opi=89978449), [Llama](https://ai.meta.com/llama/), etc. If you have an example to demo, we'd love to add it to the panel-chat-examples gallery!\n",
     "\n",
-    "![Chat Design Specification](../../assets/ChatDesignSpecification.png)\n",
+    "<img alt=\"Chat Design Specification\" src=\"../../assets/ChatDesignSpecification.png\"></img>\n",
     "\n",
     "#### Parameters:\n",
     "\n",

examples/reference/chat/ChatInterface.ipynb

@@ -29,7 +29,8 @@
     "\n",
     "Check out the [panel-chat-examples](https://holoviz-topics.github.io/panel-chat-examples/) docs to see applicable examples related to [LangChain](https://python.langchain.com/docs/get_started/introduction), [OpenAI](https://openai.com/blog/chatgpt), [Mistral](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjZtP35yvSBAxU00wIHHerUDZAQFnoECBEQAQ&url=https%3A%2F%2Fdocs.mistral.ai%2F&usg=AOvVaw2qpx09O_zOzSksgjBKiJY_&opi=89978449), [Llama](https://ai.meta.com/llama/), etc. If you have an example to demo, we'd love to add it to the panel-chat-examples gallery!\n",
     "\n",
-    "![Chat Design Specification](../../assets/ChatDesignSpecification.png)\n",
+    "<img alt=\"Chat Design Specification\" src=\"../../assets/ChatDesignSpecification.png\"></img>\n",
+    "\n",
     "#### Parameters:\n",
     "\n",
     "##### Core\n",
@@ -406,5 +407,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

examples/reference/chat/ChatMessage.ipynb

@@ -31,7 +31,7 @@
     "\n",
     "See [`ChatInterface`](ChatInterface.ipynb) for a high-level, *easy to use*, *ChatGPT like* interface.\n",
     "\n",
-    "![Chat Design Specification](../../assets/ChatDesignSpecification.png)\n",
+    "<img alt=\"Chat Design Specification\" src=\"../../assets/ChatDesignSpecification.png\"></img>\n",
     "\n",
     "#### Parameters:\n",
     "\n",

examples/reference/chat/PanelCallbackHandler.ipynb

@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "The [Langchain](https://python.langchain.com/docs/get_started/introduction) `PanelCallbackHandler` is useful for rendering and streaming *chain of thought* from Langchain objects like Tools, Agents, and Chains. It inherits from Langchain's [BaseCallbackHandler](https://python.langchain.com/docs/modules/callbacks/).\n",
+    "The [Langchain](https://python.langchain.com/docs/get_started/introduction) `PanelCallbackHandler` is useful for rendering and streaming the *chain of thought* from Langchain objects like Tools, Agents, and Chains. It inherits from Langchain's [BaseCallbackHandler](https://python.langchain.com/docs/modules/callbacks/).\n",
     "\n",
     "Check out the [panel-chat-examples](https://holoviz-topics.github.io/panel-chat-examples/langchain/) docs to see more examples on how to use `PanelCallbackHandler`. If you have an example to demo, we'd love to add it to the panel-chat-examples gallery!\n",
     "\n",
@@ -46,7 +46,7 @@
     "pn.chat.ChatInterface(callback=callback).servable()\n",
     "```\n",
     "\n",
-    "![Panel Callback Handler Basic](../../assets/panel_callback_handler_basic.png)\n",
+    "<img alt=\"Panel Callback Handler Basic\" src=\"../../assets/panel_callback_handler_basic.png\"></img>\n",
     "\n",
     "This example shows the response from the `llm` only. A `llm` by it self does not show any *chain of thought*. Later we will build an agent that uses tools. This will show *chain of thought*."
    ]
@@ -74,7 +74,7 @@
     "pn.chat.ChatInterface(callback=callback).servable()\n",
     "```\n",
     "\n",
-    "![Panel Callback Handler Basic](../../assets/panel_callback_handler_basic.png)"
+    "<img alt=\"Panel Callback Handler Basic\" src=\"../../assets/panel_callback_handler_basic.png\"></img>"
    ]
   },
   {
@@ -114,7 +114,7 @@
    "source": [
     "### Agents with Tools\n",
     "\n",
-    "Again, `async` is not required, but more efficient.\n",
+    "Tools can be used and it'll also be streamed by passing `callback_handler` to `callbacks`.\n",
     "\n",
     "```python\n",
     "from langchain.llms import OpenAI\n",
@@ -127,9 +127,9 @@
     "    tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, verbose=True, \n",
     ")\n",
     "\n",
-    "async def callback(contents, user, instance):\n",
+    "def callback(contents, user, instance):\n",
     "    callback_handler = pn.chat.langchain.PanelCallbackHandler(instance)\n",
-    "    await agent.arun(contents, callbacks=[callback_handler])\n",
+    "    return agent.run(contents, callbacks=[callback_handler])\n",
     "\n",
     "pn.chat.ChatInterface(callback=callback).servable()\n",
     "```\n",
@@ -210,7 +210,8 @@
     "async def callback(contents, user, instance):\n",
     "    callback_handler = pn.chat.langchain.PanelCallbackHandler(instance)\n",
     "    chain = get_chain(callbacks=[callback_handler])\n",
-    "    await chain.ainvoke(contents)\n",
+    "    response = await chain.ainvoke(contents)\n",
+    "    return response.content\n",
     "\n",
     "\n",
     "pn.chat.ChatInterface(callback=callback).servable()\n",
@@ -219,7 +220,7 @@
     "Please note that we use the `hack` because retrievers currently do not call any `CallbackHandler`s.\n",
     "See [LangChain Issue#7290](https://github.com/langchain-ai/langchain/issues/7290).\n",
     "\n",
-    "![PanelCallbackHandler with retriever](../../assets/panel_callback_handler_retriever.png)"
+    "<img alt=\"PanelCallbackHandler with retriever\" src=\"../../assets/panel_callback_handler_retriever.png\"></img>"
    ]
   }
  ],
@@ -230,5 +231,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

panel/chat/langchain.py

@@ -22,7 +22,8 @@
 class PanelCallbackHandler(BaseCallbackHandler):
     """
     The Langchain `PanelCallbackHandler` itself is not a widget or pane, but is useful for rendering
-    and streaming output from Langchain Tools, Agents, and Chains as `ChatMessage` objects.
+    and streaming the *chain of thought* from Langchain Tools, Agents, and Chains
+    as `ChatMessage` objects.
 
     Reference: https://panel.holoviz.org/reference/chat/PanelCallbackHandler.html
 
@@ -67,13 +68,20 @@ def _update_active(self, avatar: str, label: str):
         if f"- {label}" not in self._active_user:
             self._active_user = f"{self._active_user} - {label}"
 
+    def _reset_active(self):
+        self._active_user = self._input_user
+        self._active_avatar = self._input_avatar
+        self._message = None
+
     def _stream(self, message: str):
-        return self.instance.stream(
-            message,
-            user=self._active_user,
-            avatar=self._active_avatar,
-            message=self._message,
-        )
+        if message.strip():
+            return self.instance.stream(
+                message,
+                user=self._active_user,
+                avatar=self._active_avatar,
+                message=self._message,
+            )
+        return self._message
 
     def on_llm_start(self, serialized: Dict[str, Any], *args, **kwargs):
         model = kwargs.get("invocation_params", {}).get("model_name", "")
@@ -99,9 +107,7 @@ def on_llm_end(self, response: LLMResult, *args, **kwargs):
                 respond=False,
             )
 
-        self._active_user = self._input_user
-        self._active_avatar = self._input_avatar
-        self._message = None
+        self._reset_active()
         return super().on_llm_end(response, *args, **kwargs)
 
     def on_llm_error(self, error: Union[Exception, KeyboardInterrupt], *args, **kwargs):
@@ -117,10 +123,12 @@ def on_tool_start(
         self, serialized: Dict[str, Any], input_str: str, *args, **kwargs
     ):
         self._update_active(DEFAULT_AVATARS["tool"], serialized["name"])
+        self._stream(f"Tool input: {input_str}")
         return super().on_tool_start(serialized, input_str, *args, **kwargs)
 
     def on_tool_end(self, output: str, *args, **kwargs):
         self._stream(output)
+        self._reset_active()
         return super().on_tool_end(output, *args, **kwargs)
 
     def on_tool_error(
@@ -136,9 +144,7 @@ def on_chain_start(
         return super().on_chain_start(serialized, inputs, *args, **kwargs)
 
     def on_chain_end(self, outputs: Dict[str, Any], *args, **kwargs):
-        if 'output' in outputs: # The chain is finished. Report the result
-            self.instance.disabled = self._disabled_state
-            self._stream(outputs['output'])
+        self.instance.disabled = self._disabled_state
         return super().on_chain_end(outputs, *args, **kwargs)
 
     def on_retriever_error(

panel/tests/chat/test_langchain.py

@@ -30,7 +30,7 @@ async def callback(contents, user, instance):
         tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, callbacks=[callback_handler]
     )
     instance.send("2 + 2")
-    assert len(instance.objects) == 4
+    assert len(instance.objects) == 3
     assert instance.objects[1].object == "Action: Python REPL\nAction Input: print(2 + 2)"
     assert instance.objects[2].object == "Final Answer: 4"
-    assert instance.objects[3].object == "4"
+    assert not instance.disabled