refactor: Update prompt validation process in validate.py

Refactor the prompt validation process in validate.py to improve code readability and maintainability. The changes include:

- Update the import statement for process_prompt_template in api_utils.py.
- Remove unused imports from api_utils.py.
- Simplify the post_validate_prompt function by removing unnecessary conditional statements.
- Replace the validate_prompt function call with process_prompt_template in post_validate_prompt.

These changes enhance the efficiency and organization of the prompt validation process.

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

@@ -1,16 +1,8 @@
-from collections import defaultdict
-
 from fastapi import APIRouter, HTTPException
 from loguru import logger
 
 from langflow.api.v1.base import Code, CodeValidationResponse, PromptValidationResponse, ValidatePromptRequest
-from langflow.base.prompts.api_utils import (
-    add_new_variables_to_template,
-    get_old_custom_fields,
-    remove_old_variables_from_template,
-    update_input_variables_field,
-    validate_prompt,
-)
+from langflow.base.prompts.api_utils import process_prompt_template
 from langflow.utils.validate import validate_code
 
 # build router
@@ -32,46 +24,20 @@ def post_validate_code(code: Code):
 @router.post("/prompt", status_code=200, response_model=PromptValidationResponse)
 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:
+        if not prompt_request.frontend_node:
             return PromptValidationResponse(
-                input_variables=input_variables,
+                input_variables=[],
                 frontend_node=None,
             )
-        if not prompt_request.frontend_node.custom_fields:
-            prompt_request.frontend_node.custom_fields = defaultdict(list)
-        old_custom_fields = get_old_custom_fields(prompt_request.frontend_node.custom_fields, prompt_request.name)
 
-        add_new_variables_to_template(
-            input_variables,
-            prompt_request.frontend_node.custom_fields,
-            prompt_request.frontend_node.template,
-            prompt_request.name,
+        # Process the prompt template using direct attributes
+        input_variables = process_prompt_template(
+            template=prompt_request.template,
+            name=prompt_request.name,
+            custom_fields=prompt_request.frontend_node.custom_fields,
+            frontend_node_template=prompt_request.frontend_node.template,
         )
 
-        remove_old_variables_from_template(
-            old_custom_fields,
-            input_variables,
-            prompt_request.frontend_node.custom_fields,
-            prompt_request.frontend_node.template,
-            prompt_request.name,
-        )
-
-        update_input_variables_field(input_variables, prompt_request.frontend_node.template)
-
-        # If frontend_node.template contains only one field that is type == 'prompt', then we can remove all fields that are not
-        # 'code', and not in the input_variables list.
-        prompt_fields = [
-            key
-            for key, field in prompt_request.frontend_node.template.items()
-            if isinstance(field, dict) and field["type"] == "prompt"
-        ]
-
-        if len(prompt_fields) == 1:
-            for key, field in prompt_request.frontend_node.template.copy().items():
-                if isinstance(field, dict) and field["type"] != "code" and key not in input_variables + prompt_fields:
-                    del prompt_request.frontend_node.template[key]
         return PromptValidationResponse(
             input_variables=input_variables,
             frontend_node=prompt_request.frontend_node,

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

@@ -1,10 +1,13 @@
+from collections import defaultdict
+from typing import Any, Dict, List, Optional
+
 from fastapi import HTTPException
+from langchain_core.prompts import PromptTemplate
 from loguru import logger
 
 from langflow.api.v1.base import INVALID_NAMES, check_input_variables
 from langflow.interface.utils import extract_input_variables_from_prompt
 from langflow.template.field.prompt import DefaultPromptField
-from langchain_core.prompts import PromptTemplate
 
 
 def validate_prompt(prompt_template: str, silent_errors: bool = False) -> list[str]:
@@ -81,3 +84,45 @@ def remove_old_variables_from_template(old_custom_fields, input_variables, custo
 def update_input_variables_field(input_variables, template):
     if "input_variables" in template:
         template["input_variables"]["value"] = input_variables
+
+
+def process_prompt_template(
+    template: str, name: str, custom_fields: Optional[Dict[str, List[str]]], frontend_node_template: Dict[str, Any]
+):
+    """Process and validate prompt template, update template and custom fields."""
+    # Validate the prompt template and extract input variables
+    input_variables = validate_prompt(template)
+
+    # Initialize custom_fields if None
+    if custom_fields is None:
+        custom_fields = defaultdict(list)
+
+    # Retrieve old custom fields
+    old_custom_fields = get_old_custom_fields(custom_fields, name)
+
+    # Add new variables to the template
+    add_new_variables_to_template(input_variables, custom_fields, frontend_node_template, name)
+
+    # Remove old variables from the template
+    remove_old_variables_from_template(old_custom_fields, input_variables, custom_fields, frontend_node_template, name)
+
+    # Update the input variables field in the template
+    update_input_variables_field(input_variables, frontend_node_template)
+
+    # Optional: cleanup fields based on specific conditions
+    cleanup_prompt_template_fields(input_variables, frontend_node_template)
+
+    return input_variables
+
+
+def cleanup_prompt_template_fields(input_variables, template):
+    """Removes unused fields if the conditions are met in the template."""
+    prompt_fields = [
+        key for key, field in template.items() if isinstance(field, dict) and field.get("type") == "prompt"
+    ]
+
+    if len(prompt_fields) == 1:
+        for key in list(template.keys()):  # Use list to copy keys
+            field = template.get(key, {})
+            if isinstance(field, dict) and field.get("type") != "code" and key not in input_variables + prompt_fields:
+                del template[key]