fix(prompt): warn when custom template directory doesn't exist

Author: jiezhuzzz

openevolve/prompt/templates.py

@@ -4,9 +4,12 @@
 
 import os
 import json
+import logging
 from pathlib import Path
 from typing import Dict, List, Optional, Union, Any
 
+logger = logging.getLogger(__name__)
+
 # Base system message template for evolution
 BASE_SYSTEM_TEMPLATE = """You are an expert software developer tasked with iteratively improving a codebase.
 Your job is to analyze the current program and suggest improvements based on feedback from previous attempts.
@@ -185,8 +188,13 @@ def __init__(self, custom_template_dir: Optional[str] = None):
         self._load_from_directory(self.default_dir)
 
         # 2. Override with custom templates (if provided)
-        if self.custom_dir and self.custom_dir.exists():
-            self._load_from_directory(self.custom_dir)
+        if self.custom_dir:
+            if self.custom_dir.exists():
+                self._load_from_directory(self.custom_dir)
+            else:
+                logger.warning(
+                    f"Custom template directory does not exist, using default prompt."
+                )
 
     def _load_from_directory(self, directory: Path) -> None:
         """Load all templates and fragments from a directory"""