🐛 fix(base.py): fix logic for checking and fixing input variables in check_input_variables function

🔍 refactor(base.py): refactor build_error_message function to improve readability and error message generation

The check_input_variables function now correctly handles empty variables and variables that start with a number. It removes invalid characters from the variables and adds them to the wrong_variables set. The build_error_message function has been refactored to generate a more informative error message, including details about invalid characters, wrong variables, empty variables, and duplicate variables. This improves the clarity of error messages when validating input variables.

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

@@ -71,30 +71,68 @@ def validate_prompt(template: str):
     except Exception as exc:
         raise ValueError(str(exc)) from exc
 
-    # if len(input_variables) > 1:
-    #     # If there's more than one input variable
-
     return input_variables
 
 
 def check_input_variables(input_variables: list):
     invalid_chars = []
     fixed_variables = []
+    wrong_variables = set()
+    empty_variables = []
     for variable in input_variables:
         new_var = variable
+
+        # if variable is empty, then we should add that to the wrong variables
+        if not variable:
+            empty_variables.append(variable)
+            continue
+
+        # if variable starts with a number we should add that to the invalid chars
+        # and wrong variables
+        if variable[0].isdigit():
+            invalid_chars.append(variable[0])
+            new_var = new_var.replace(variable[0], "")
+            wrong_variables.add(variable)
+
         for char in INVALID_CHARACTERS:
             if char in variable:
                 invalid_chars.append(char)
                 new_var = new_var.replace(char, "")
+                wrong_variables.add(variable)
         fixed_variables.append(new_var)
-        if new_var != variable:
-            input_variables.remove(variable)
-            input_variables.append(new_var)
+        # if new_var != variable and new_var not in input_variables:
+        #     input_variables.remove(variable)
+        #     input_variables.append(new_var)
     # If any of the input_variables is not in the fixed_variables, then it means that
     # there are invalid characters in the input_variables
-    if any(var not in fixed_variables for var in input_variables):
-        raise ValueError(
-            f"Invalid input variables: {input_variables}. Please, use something like {fixed_variables} instead."
-        )
 
+    if any(var not in fixed_variables for var in input_variables):
+        error_message = build_error_message(
+            input_variables,
+            invalid_chars,
+            wrong_variables,
+            fixed_variables,
+            empty_variables,
+        )
+        raise ValueError(error_message)
     return input_variables
+
+
+def build_error_message(
+    input_variables, invalid_chars, wrong_variables, fixed_variables, empty_variables
+):
+    input_variables_str = ", ".join([f"'{var}'" for var in input_variables])
+    error_string = f"Invalid input variables: {input_variables_str}."
+
+    if wrong_variables and invalid_chars:
+        ", ".join([f"'{var}'" for var in wrong_variables])
+        invalid_chars_str = ", ".join([f"'{char}'" for char in invalid_chars])
+        error_string += (
+            f" Please, remove the invalid characters: {invalid_chars_str}"
+            " from the variables: {wrong_variables_str}."
+        )
+    elif empty_variables:
+        error_string += f" There are {len(empty_variables)} empty variable{'s' if len(empty_variables) > 1 else ''}."
+    elif len(set(fixed_variables)) != len(fixed_variables):
+        error_string += " There are duplicate variables."
+    return error_string