fix(api): make frontend_node field optional in ValidatePromptRequest to allow for a tweak call without a frontend_node

fix(api): handle case where frontend_node is None in post_validate_prompt to avoid attempting to update a non-existent node

src/backend/langflow/api/v1/base.py

@@ -1,3 +1,4 @@
+from typing import Optional
 from langflow.template.frontend_node.base import FrontendNode
 from pydantic import BaseModel, validator
 
@@ -20,7 +21,8 @@ class FrontendNodeRequest(FrontendNode):
 class ValidatePromptRequest(BaseModel):
     name: str
     template: str
-    frontend_node: FrontendNodeRequest
+    #optional for tweak call
+    frontend_node: Optional[FrontendNodeRequest]
 
 
 # Build ValidationResponse class for {"imports": {"errors": []}, "function": {"errors": []}}
@@ -39,7 +41,8 @@ class CodeValidationResponse(BaseModel):
 
 class PromptValidationResponse(BaseModel):
     input_variables: list
-    frontend_node: FrontendNodeRequest
+    #object return for tweak call
+    frontend_node: FrontendNodeRequest | object
 
 
 INVALID_CHARACTERS = {

src/backend/langflow/api/v1/validate.py

@@ -31,7 +31,12 @@ def post_validate_code(code: Code):
 def post_validate_prompt(prompt_request: ValidatePromptRequest):
     try:
         input_variables = validate_prompt(prompt_request.template)
-
+        # Check if frontend_node is None before proceeding to avoid attempting to update a non-existent node.
+        if prompt_request.frontend_node is None:
+            return PromptValidationResponse(
+                input_variables=input_variables,
+                frontend_node={},
+            )
         old_custom_fields = get_old_custom_fields(prompt_request)
 
         add_new_variables_to_template(input_variables, prompt_request)