fix: prevent JSON content from being added multiple times during retries (#1255)

test/oai/test_base.py

@@ -0,0 +1,23 @@
+import pytest
+
+
+class MockBackend:
+    def __init__(self):
+        self.messages = []
+
+    def _add_json_in_prompt(self, new_messages):
+        self.messages.append("JSON_ADDED")
+
+
+def test_json_added_once():
+    backend = MockBackend()
+    try_n = 3
+    json_added = False
+    new_messages = ["msg1"]
+
+    for _ in range(try_n):
+        if not json_added:
+            backend._add_json_in_prompt(new_messages)
+            json_added = True
+
+    assert backend.messages.count("JSON_ADDED") == 1