fix: make ChatMessage.from_dict handle cases where optional fields are missing (#9232)

* fix: make ChatMessage.from_dict handle cases where optional fields are missing

* one more test

haystack/dataclasses/chat_message.py

@@ -361,7 +361,11 @@ class ChatMessage:
             The created object.
         """
         if "content" in data:
-            init_params = {"_role": ChatRole(data["role"]), "_name": data["name"], "_meta": data["meta"]}
+            init_params: Dict[str, Any] = {
+                "_role": ChatRole(data["role"]),
+                "_name": data.get("name"),
+                "_meta": data.get("meta") or {},
+            }
 
             if isinstance(data["content"], list):
                 # current format - the serialized `content` field is a list of dictionaries
@@ -378,8 +382,8 @@ class ChatMessage:
             return cls(
                 _role=ChatRole(data["_role"]),
                 _content=_deserialize_content(data["_content"]),
-                _name=data["_name"],
-                _meta=data["_meta"],
+                _name=data.get("_name"),
+                _meta=data.get("_meta") or {},
             )
 
         raise ValueError(f"Missing 'content' or '_content' in serialized ChatMessage: `{data}`")

releasenotes/notes/chatmessage-from-dict-fix-bd361b59071651ae.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fix `ChatMessage.from_dict` to handle cases where optional fields like `name` and `meta` are missing.

test/dataclasses/test_chat_message.py

@@ -226,6 +226,16 @@ def test_from_dict_with_pre29_format():
     assert msg.meta == {"some": "info"}
 
 
+def test_from_dict_with_pre29_format_some_fields_missing():
+    serialized_msg_pre_29 = {"role": "user", "content": "This is a message"}
+    msg = ChatMessage.from_dict(serialized_msg_pre_29)
+
+    assert msg.role == ChatRole.USER
+    assert msg._content == [TextContent(text="This is a message")]
+    assert msg.name is None
+    assert msg.meta == {}
+
+
 def test_from_dict_with_pre212_format():
     """
     Test that we can deserialize messages serialized with versions >=2.9.0 and <2.12.0,
@@ -245,6 +255,26 @@ def test_from_dict_with_pre212_format():
     assert msg.meta == {"some": "info"}
 
 
+def test_from_dict_with_pre212_format_some_fields_missing():
+    serialized_msg_pre_212 = {"_role": "user", "_content": [{"text": "This is a message"}]}
+    msg = ChatMessage.from_dict(serialized_msg_pre_212)
+
+    assert msg.role == ChatRole.USER
+    assert msg._content == [TextContent(text="This is a message")]
+    assert msg.name is None
+    assert msg.meta == {}
+
+
+def test_from_dict_some_fields_missing():
+    serialized_msg = {"role": "user", "content": [{"text": "This is a message"}]}
+    msg = ChatMessage.from_dict(serialized_msg)
+
+    assert msg.role == ChatRole.USER
+    assert msg._content == [TextContent(text="This is a message")]
+    assert msg.name is None
+    assert msg.meta == {}
+
+
 def test_from_dict_missing_content_field():
     serialized_msg = {"role": "user", "name": "some_name", "meta": {"some": "info"}}
     with pytest.raises(ValueError):