feat: added custom conversation chains and prompts

src/backend/langflow/config.yaml

@@ -3,6 +3,9 @@ chains:
   - LLMMathChain
   - LLMCheckerChain
   - ConversationChain
+  - SeriesCharacterChain
+  - MidJourneyPromptChain
+  - TimeTravelGuideChain
 
 agents:
   - ZeroShotAgent

src/backend/langflow/graph/nodes.py

@@ -75,7 +75,9 @@ class PromptNode(Node):
             for param in prompt_params:
                 prompt_text = self.params[param]
                 variables = extract_input_variables_from_prompt(prompt_text)
+
                 self.params["input_variables"].extend(variables)
+            self.params["input_variables"] = list(set(self.params["input_variables"]))
 
             self._build()
         return deepcopy(self._built_object)

src/backend/langflow/interface/chains/base.py

@@ -1,4 +1,5 @@
 from typing import Dict, List, Optional
+from langflow.custom.customs import get_custom_nodes
 
 from langflow.interface.base import LangChainTypeCreator
 from langflow.interface.custom_lists import chain_type_to_cls_dict
@@ -15,19 +16,27 @@ class ChainCreator(LangChainTypeCreator):
     def type_to_loader_dict(self) -> Dict:
         if self.type_dict is None:
             self.type_dict = chain_type_to_cls_dict
+            from langflow.interface.chains.custom import CUSTOM_CHAINS
+
+            self.type_dict.update(CUSTOM_CHAINS)
         return self.type_dict
 
     def get_signature(self, name: str) -> Optional[Dict]:
         try:
-            return build_template_from_class(name, chain_type_to_cls_dict)
+            if name in get_custom_nodes(self.type_name).keys():
+                return get_custom_nodes(self.type_name)[name]
+            return build_template_from_class(name, self.type_to_loader_dict)
         except ValueError as exc:
-            raise ValueError("Memory not found") from exc
+            raise ValueError("Chain not found") from exc
 
     def to_list(self) -> List[str]:
+        custom_chains = list(get_custom_nodes("chains").keys())
+        default_chains = list(self.type_to_loader_dict.keys())
+        # Check if the chain is in the settings
         return [
-            chain.__name__
-            for chain in self.type_to_loader_dict.values()
-            if chain.__name__ in settings.chains or settings.dev
+            chain
+            for chain in default_chains + custom_chains
+            if chain in settings.chains or settings.dev
         ]
 
 

src/backend/langflow/interface/chains/custom.py

@@ -0,0 +1,100 @@
+from typing import Optional
+from langchain.chains import ConversationChain
+from langflow.graph.utils import extract_input_variables_from_prompt
+from pydantic import root_validator, Field
+from langchain.memory.buffer import ConversationBufferMemory
+from langchain.schema import BaseMemory
+
+
+DEFAULT_SUFFIX = """"
+Current conversation:
+{history}
+Human: {input}
+{ai_prefix}"""
+
+
+class BaseCustomChain(ConversationChain):
+    """BaseCustomChain is a chain you can use to have a conversation with a custom character."""
+
+    template: Optional[str]
+
+    ai_prefix_key: Optional[str]
+    """Field to use as the ai_prefix. It needs to be set and has to be in the template"""
+
+    @root_validator(pre=False)
+    def build_template(cls, values):
+        format_dict = {}
+        input_variables = extract_input_variables_from_prompt(values["template"])
+
+        if values.get("ai_prefix_key", None) is None:
+            values["ai_prefix_key"] = values["memory"].ai_prefix
+
+        for key in input_variables:
+            new_value = values.get(key, f"{{{key}}}")
+            format_dict[key] = new_value
+            if key == values.get("ai_prefix_key", None):
+                values["memory"].ai_prefix = new_value
+
+        values["template"] = values["template"].format(**format_dict)
+
+        values["template"] = values["template"]
+        values["input_variables"] = extract_input_variables_from_prompt(
+            values["template"]
+        )
+        values["prompt"].template = values["template"]
+        values["prompt"].input_variables = values["input_variables"]
+        return values
+
+
+class SeriesCharacterChain(BaseCustomChain):
+    """SeriesCharacterChain is a chain you can use to have a conversation with a character from a series."""
+
+    character: str
+    series: str
+    template: Optional[
+        str
+    ] = """I want you to act like {character} from {series}.
+I want you to respond and answer like {character}. do not write any explanations. only answer like {character}.
+You must know all of the knowledge of {character}.
+Current conversation:
+{history}
+Human: {input}
+{character}:"""
+    memory: BaseMemory = Field(default_factory=ConversationBufferMemory)
+    ai_prefix_key: Optional[str] = "character"
+    """Default memory store."""
+
+
+class MidJourneyPromptChain(BaseCustomChain):
+    """MidJourneyPromptChain is a chain you can use to generate new MidJourney prompts."""
+
+    template: Optional[
+        str
+    ] = """I want you to act as a prompt generator for Midjourney's artificial intelligence program.
+    Your job is to provide detailed and creative descriptions that will inspire unique and interesting images from the AI.
+    Keep in mind that the AI is capable of understanding a wide range of language and can interpret abstract concepts, so feel free to be as imaginative and descriptive as possible.
+    For example, you could describe a scene from a futuristic city, or a surreal landscape filled with strange creatures.
+    The more detailed and imaginative your description, the more interesting the resulting image will be. Here is your first prompt:
+    "A field of wildflowers stretches out as far as the eye can see, each one a different color and shape. In the distance, a massive tree towers over the landscape, its branches reaching up to the sky like tentacles.\"
+
+    Current conversation:
+    {history}
+    Human: {input}
+    AI:"""
+
+
+class TimeTravelGuideChain(BaseCustomChain):
+    template: Optional[
+        str
+    ] = """I want you to act as my time travel guide. You are helpful and creative. I will provide you with the historical period or future time I want to visit and you will suggest the best events, sights, or people to experience. Provide the suggestions and any necessary information.
+    Current conversation:
+    {history}
+    Human: {input}
+    AI:"""
+
+
+CUSTOM_CHAINS = {
+    "SeriesCharacterChain": SeriesCharacterChain,
+    "MidJourneyPromptChain": MidJourneyPromptChain,
+    "TimeTravelGuideChain": TimeTravelGuideChain,
+}

src/backend/langflow/interface/importing/utils.py

@@ -10,6 +10,7 @@ from langchain.chat_models.base import BaseChatModel
 from langchain.llms.base import BaseLLM
 from langchain.tools import BaseTool
 
+
 from langflow.interface.tools.util import get_tool_by_name
 
 
@@ -66,9 +67,13 @@ def import_class(class_path: str) -> Any:
 
 
 def import_prompt(prompt: str) -> PromptTemplate:
+    from langflow.interface.prompts.custom import CUSTOM_PROMPTS
+
     """Import prompt from prompt name"""
     if prompt == "ZeroShotPrompt":
         return import_class("langchain.prompts.PromptTemplate")
+    elif prompt in CUSTOM_PROMPTS:
+        return CUSTOM_PROMPTS[prompt]
     return import_class(f"langchain.prompts.{prompt}")
 
 
@@ -102,4 +107,8 @@ def import_tool(tool: str) -> BaseTool:
 
 def import_chain(chain: str) -> Chain:
     """Import chain from chain name"""
+    from langflow.interface.chains.custom import CUSTOM_CHAINS
+
+    if chain in CUSTOM_CHAINS:
+        return CUSTOM_CHAINS[chain]
     return import_class(f"langchain.chains.{chain}")

src/backend/langflow/interface/prompts/base.py

@@ -26,6 +26,10 @@ class PromptCreator(LangChainTypeCreator):
                 for prompt_name in prompts.__all__
                 if not prompt_name.islower() and prompt_name in settings.prompts
             }
+            # Merge CUSTOM_PROMPTS into self.type_dict
+            from langflow.interface.prompts.custom import CUSTOM_PROMPTS
+
+            self.type_dict.update(CUSTOM_PROMPTS)
         return self.type_dict
 
     def get_signature(self, name: str) -> Optional[Dict]:

src/backend/langflow/interface/prompts/custom.py

@@ -1,4 +1,4 @@
-from typing import List, Optional
+from typing import Dict, List, Optional
 
 from langchain.prompts import PromptTemplate
 from pydantic import root_validator
@@ -7,43 +7,49 @@ from langflow.graph.utils import extract_input_variables_from_prompt
 from langflow.template.base import Template, TemplateField
 from langflow.template.nodes import PromptTemplateNode
 
-CHARACTER_PROMPT = """I want you to act like {character} from {series}.
-I want you to respond and answer like {character}. do not write any explanations. only answer like {character}.
-You must know all of the knowledge of {character}."""
+
+# Steps to create a BaseCustomPrompt:
+# 1. Create a prompt template that endes with:
+#    Current conversation:
+#     {history}
+#    Human: {input}
+#    {ai_prefix}:
+# 2. Create a class that inherits from BaseCustomPrompt
+# 3. Add the following class attributes:
+#    template: str = ""
+#    description: Optional[str]
+#    ai_prefix: Optional[str] = "{ai_prefix}"
+# 3.1. The ai_prefix should be a value in input_variables
+# SeriesCharacterPrompt is a working example
+# If used in a LLMChain, with a Memory module, it will work as expected
+# We should consider creating ConversationalChains that expose custom parameters
+# That way it will be easier to create custom prompts
 
 
 class BaseCustomPrompt(PromptTemplate):
     template: str = ""
     description: Optional[str]
-    human_text: str = "\n {input}"
+    ai_prefix: Optional[str]
 
     @root_validator(pre=False)
     def build_template(cls, values):
         format_dict = {}
+        ai_prefix_format_dict = {}
         for key in values.get("input_variables", []):
-            new_value = values[key]
+            new_value = values.get(key, f"{{{key}}}")
             format_dict[key] = new_value
+            if key in values["ai_prefix"]:
+                ai_prefix_format_dict[key] = new_value
 
+        values["ai_prefix"] = values["ai_prefix"].format(**ai_prefix_format_dict)
         values["template"] = values["template"].format(**format_dict)
 
-        values["template"] = values["template"] + values["human_text"]
+        values["template"] = values["template"]
         values["input_variables"] = extract_input_variables_from_prompt(
             values["template"]
         )
         return values
 
-    def build_frontend_node(self) -> PromptTemplateNode:
-        return PromptTemplateNode(
-            template=Template(
-                type_name="test",
-                fields=[
-                    TemplateField(name=field, field_type="str", required=True)
-                    for field in self.input_variables
-                ],
-            ),
-            description=self.description or "",
-        )
-
 
 class SeriesCharacterPrompt(BaseCustomPrompt):
     # Add a very descriptive description for the prompt generator
@@ -52,14 +58,21 @@ class SeriesCharacterPrompt(BaseCustomPrompt):
     ] = "A prompt that asks the AI to act like a character from a series."
     character: str
     series: str
-    human_text: str = "\n {input}"
-    template: str = CHARACTER_PROMPT
+    template: str = """I want you to act like {character} from {series}.
+I want you to respond and answer like {character}. do not write any explanations. only answer like {character}.
+You must know all of the knowledge of {character}.
 
+Current conversation:
+{history}
+Human: {input}
+{character}:"""
+
+    ai_prefix: str = "{character}"
     input_variables: List[str] = ["character", "series"]
 
 
+CUSTOM_PROMPTS = {"SeriesCharacterPrompt": SeriesCharacterPrompt}
+
 if __name__ == "__main__":
-    prompt = SeriesCharacterPrompt(character="Walter White", series="Breaking Bad")
-    user_input = "I am the one who knocks"
-    full_prompt = prompt.format(input=user_input)
-    print(full_prompt)
+    prompt = SeriesCharacterPrompt(character="Harry Potter", series="Harry Potter")
+    print(prompt.template)

src/backend/langflow/interface/run.py

@@ -52,6 +52,12 @@ def process_graph(data_graph: Dict[str, Any]):
     )
     logger.debug("Loaded langchain object")
 
+    if langchain_object is None:
+        # Raise user facing error
+        raise ValueError(
+            "There was an error loading the flow. Please, check all the nodes and try again."
+        )
+
     # Generate result and thought
     logger.debug("Generating result and thought")
     result, thought = get_result_and_thought_using_graph(langchain_object, message)
@@ -73,18 +79,30 @@ def get_result_and_thought_using_graph(loaded_langchain, message: str):
             loaded_langchain.verbose = True
         with io.StringIO() as output_buffer, contextlib.redirect_stdout(output_buffer):
             chat_input = None
+            memory_key = ""
+            if hasattr(loaded_langchain, "memory"):
+                mem_vars = loaded_langchain.memory.memory_variables
+                memory_key = mem_vars[0] if mem_vars else ""
+
             for key in loaded_langchain.input_keys:
-                if key == "chat_history" and hasattr(loaded_langchain, "memory"):
-                    loaded_langchain.memory.memory_key = "chat_history"
-                else:
+                if key != memory_key:
                     chat_input = {key: message}
 
             if hasattr(loaded_langchain, "return_intermediate_steps"):
                 # https://github.com/hwchase17/langchain/issues/2068
                 loaded_langchain.return_intermediate_steps = False
 
+            # I'm not sure about this yet.
+            function_to_call = None
+            if hasattr(loaded_langchain, "memory"):
+            elif hasattr(loaded_langchain, "run"):
+                function_to_call = loaded_langchain.run
+                function_to_call = loaded_langchain.predict
+            else:
+                function_to_call = loaded_langchain
+
             try:
-                output = loaded_langchain(chat_input)
+                output = function_to_call(chat_input)
             except ValueError as exc:
                 logger.debug("Error: %s", str(exc))
                 output = loaded_langchain.run(chat_input)

src/backend/langflow/template/nodes.py

@@ -251,7 +251,7 @@ class PromptFrontendNode(FrontendNode):
             field.field_type = "str"
             field.multiline = True
             field.value = HUMAN_PROMPT if "Human" in field.name else SYSTEM_PROMPT
-        if field.name == "template":
+        if field.name == "template" and field.value == "":
             field.value = DEFAULT_PROMPT
 
         if (