feat: add LangChain Hub Component (#2990)

* #2822 LangSmith Hub Component

* [autofix.ci] apply automated fixes

* Update __init__.py

* Move and restructure langsmith prompt component

* [autofix.ci] apply automated fixes

* Fix imports

* Update __init__.py

* Update LangSmithPrompt.py

* Next pass at component for langchain hub

* [autofix.ci] apply automated fixes

* Return a chat prompt template

* [autofix.ci] apply automated fixes

* Create OpenAIToolsAgentPrompt.py

* Update OpenAIToolsAgentPrompt.py

* Delete OpenAIToolsAgentPrompt.py

* FIX remove old fields when refreshing

* [autofix.ci] apply automated fixes

* Return a Message object

* [autofix.ci] apply automated fixes

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Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/base/langflow/components/prompts/LangChainHubPrompt.py

@@ -0,0 +1,109 @@
+from typing import List
+
+from langflow.custom import Component
+from langflow.inputs import StrInput, SecretStrInput, DefaultPromptField
+from langflow.io import Output
+from langflow.schema.message import Message
+
+
+import re
+
+
+class LangChainHubPromptComponent(Component):
+    display_name: str = "LangChain Hub Prompt Component"
+    description: str = "Prompt Component that uses LangChain Hub prompts"
+    beta = True
+    icon = "prompts"
+    trace_type = "prompt"
+    name = "LangChain Hub Prompt"
+
+    inputs = [
+        SecretStrInput(
+            name="langchain_api_key",
+            display_name="Your LangChain API Key",
+            info="The LangChain API Key to use.",
+        ),
+        StrInput(
+            name="langchain_hub_prompt",
+            display_name="LangChain Hub Prompt",
+            info="The LangChain Hub prompt to use.",
+            value="efriis/my-first-prompt",
+            refresh_button=True,
+        ),
+    ]
+
+    outputs = [
+        Output(display_name="Build Prompt", name="prompt", method="build_prompt"),
+    ]
+
+    def update_build_config(self, build_config: dict, field_value: str, field_name: str | None = None):
+        if field_name == "langchain_hub_prompt":
+            template = self._fetch_langchain_hub_template()
+
+            # Extract the messages from the prompt data
+            prompt_template = []
+            for message_data in template.messages:
+                prompt_template.append(message_data.prompt)
+
+            # Regular expression to find all instances of {<string>}
+            pattern = r"\{(.*?)\}"
+
+            # Get all the custom fields
+            custom_fields: List[str] = []
+            full_template = ""
+            for message in prompt_template:
+                # Find all matches
+                matches = re.findall(pattern, message.template)
+                custom_fields = custom_fields + matches
+
+                # Create a string version of the full template
+                full_template = full_template + "\n" + message.template
+
+            # No need to reprocess if we have them already
+            if all(["param_" + custom_field in build_config for custom_field in custom_fields]):
+                return build_config
+
+            # Easter egg: Show template in info popup
+            build_config["langchain_hub_prompt"]["info"] = full_template
+
+            # Remove old parameter inputs if any
+            for key, _ in build_config.copy().items():
+                if key.startswith("param_"):
+                    del build_config[key]
+
+            # Now create inputs for each
+            for custom_field in custom_fields:
+                new_parameter = DefaultPromptField(
+                    name=f"param_{custom_field}",
+                    display_name=custom_field,
+                    info="Fill in the value for {" + custom_field + "}",
+                ).to_dict()
+
+                build_config[f"param_{custom_field}"] = new_parameter
+
+        return build_config
+
+    async def build_prompt(
+        self,
+    ) -> Message:
+        # Get the parameters that
+        template = self._fetch_langchain_hub_template()  # TODO: doing this twice
+        original_params = {k[6:] if k.startswith("param_") else k: v for k, v in self._attributes.items()}
+        prompt_value = template.invoke(original_params)
+
+        original_params["template"] = prompt_value.to_string()
+
+        # Now pass the filtered attributes to the function
+        prompt = await Message.from_template_and_variables(**original_params)
+
+        self.status = prompt.text
+
+        return prompt
+
+    def _fetch_langchain_hub_template(self):
+        import langchain.hub
+
+        # Pull the prompt from LangChain Hub
+        prompt_data = langchain.hub.pull(self.langchain_hub_prompt, api_key=self.langchain_api_key)
+
+        return prompt_data

src/backend/base/langflow/components/prompts/__init__.py

@@ -1,3 +1,4 @@
 from .Prompt import PromptComponent
+from .LangChainHubPrompt import LangChainHubPromptComponent
 
-__all__ = ["PromptComponent"]
+__all__ = ["PromptComponent", "LangChainHubPromptComponent"]