feat(workflow): support variables wrapped with {{}} in assignment nodes, add input config example

api/app/core/workflow/nodes/assigner/config.py

@@ -30,3 +30,18 @@ class AssignerNodeConfig(BaseNodeConfig):
         ...,
         description="List of variable assignment definitions",
     )
+
+    class Config:
+        json_schema_extra = {
+            "examples": [
+                {
+                    "assignments": [
+                        {
+                            "variable_selector": "{{ conv.test1 }}",
+                            "operation": "add",
+                            "value": "3"
+                        }
+                    ]
+                }
+            ]
+        }

api/app/core/workflow/nodes/assigner/node.py

@@ -1,4 +1,5 @@
 import logging
+import re
 from typing import Any
 
 from app.core.workflow.expression_evaluator import ExpressionEvaluator
@@ -34,7 +35,9 @@ class AssignerNode(BaseNode):
             variable_selector = assignment.variable_selector
             if isinstance(variable_selector, str):
                 # Support dot-separated string paths, e.g., "conv.test" -> ["conv", "test"]
-                variable_selector = variable_selector.split('.')
+                pattern = r"\{\{\s*(.*?)\s*\}\}"
+                expression = re.sub(pattern, r"\1", variable_selector).strip()
+                variable_selector = expression.split('.')
 
             # Only conversation variables ('conv') are allowed
             if variable_selector[0] != 'conv':  # TODO: Loop node variable support (Feature)