addresses PR review

lib/services/rocket.py

@@ -236,11 +236,16 @@ def check_parachute_trigger(expression: str) -> bool:
             bool: True if the expression is valid, False otherwise.
         """
 
+        class InvalidParachuteTrigger(Exception):
+            pass
+
         # Parsing the expression into an AST
         try:
             parsed_expression = ast.parse(expression, mode="eval")
-        except SyntaxError:
-            raise SyntaxError("Invalid expression syntax.")
+        except SyntaxError as e:
+            raise InvalidParachuteTrigger(
+                f"Invalid expression syntax: {str(e)}"
+            ) from None
 
         # Constant case (supported after beta v1)
         if isinstance(parsed_expression.body, ast.Constant):
@@ -254,32 +259,36 @@ def check_parachute_trigger(expression: str) -> bool:
 
         # Validating the expression structure
         if not isinstance(parsed_expression.body, ast.Lambda):
-            raise SyntaxError("Invalid expression structure: not a Lambda.")
+            raise InvalidParachuteTrigger(
+                "Invalid expression structure: not a lambda."
+            ) from None
 
         lambda_node = parsed_expression.body
         if len(lambda_node.args.args) != 3:
-            raise SyntaxError("Invalid expression structure: invalid arity.")
+            raise InvalidParachuteTrigger(
+                "Invalid expression structure: lambda should have 3 arguments."
+            ) from None
 
         if not isinstance(lambda_node.body, ast.Compare):
             try:
                 for operand in lambda_node.body.values:
                     if not isinstance(operand, ast.Compare):
-                        raise SyntaxError(
-                            "Invalid expression structure (not a Compare)."
-                        )
+                        raise InvalidParachuteTrigger(
+                            "Invalid expression structure: not a Compare."
+                        ) from None
             except AttributeError:
-                raise SyntaxError(
-                    "Invalid expression structure (not a Compare)."
-                )
+                raise InvalidParachuteTrigger(
+                    "Invalid expression structure: not a Compare."
+                ) from None
 
         # Restricting access to functions or attributes
         for node in ast.walk(lambda_node):
             if isinstance(node, ast.Call):
-                raise SyntaxError(
+                raise InvalidParachuteTrigger(
                     "Calling functions is not allowed in the expression."
-                )
+                ) from None
             if isinstance(node, ast.Attribute):
-                raise SyntaxError(
+                raise InvalidParachuteTrigger(
                     "Accessing attributes is not allowed in the expression."
-                )
+                ) from None
         return True