[Bug]: @field_validator for url in ImageBlock does not handle None correctly

[malsaraa]

Bug Description

My chat messages are managed outside the basic llama-index framework (i.e., not using chat stores, etc.) because the bot is a Teams app. These messages are stored as JSON and retrieved as needed, then converted into a list of ChatMessage. However, I'm currently trying to integrate ImageBlock and encountering a ValidationError.

The ImageBlock model’s url field is declared as AnyUrl | str | None, which suggests that None should be an accepted value. However, the @field_validator for the url field does not account for None. As a result, attempting to pass None for the url field results in a TypeError when the validator tries to convert it to AnyUrl.

I assume that the validator needs a minor update to handle the None

def urlstr_to_anyurl(cls, url: str | AnyUrl | None) -> AnyUrl | None:
   if url is None:
       return None
   if isinstance(url, AnyUrl):
       return url
   return AnyUrl(url=url)

Version

0.12.7

Steps to Reproduce

Example code:

def serialize_message(obj):
    if isinstance(obj, Path):
        return str(obj)
    if isinstance(obj, ChatMessage):
        return obj.model_dump()
    raise TypeError(f"Type {type(obj)} not serializable")


def deserialize_message(obj):
    if 'path' in obj:
        obj['path'] = Path(obj['path'])
    return obj


test_message = ChatMessage(
                role="user",
                content=[
                    TextBlock(text="test-message-text"),
                    ImageBlock(path=local_image_path, image_mimetype='image/jpeg'),
                ],
            )

jsonStr = json.dumps(test_message.model_dump(), default=serialize_message)

converted = json.loads(jsonStr, object_hook=deserialize_message)

new_message = ChatMessage(**converted)

Relevant Logs/Tracbacks

ValidationError                           Traceback (most recent call last)
Cell In[2], line 31
     27 jsonStr = json.dumps(test_message.model_dump(), default=serialize_message)
     29 converted = json.loads(jsonStr, object_hook=deserialize_message)
---> 31 new_message = ChatMessage(**converted)

File c:\Users\user\AppData\Local\miniconda3\envs\llama\Lib\site-packages\llama_index\core\base\llms\types.py:142, in ChatMessage.__init__(self, content, **data)
    139     elif isinstance(content, list):
    140         data["blocks"] = content
--> 142 super().__init__(**data)

File c:\Users\user\AppData\Local\miniconda3\envs\llama\Lib\site-packages\pydantic\main.py:214, in BaseModel.__init__(self, **data)
    212 # `__tracebackhide__` tells pytest and some other tools to omit this function from tracebacks
    213 __tracebackhide__ = True
--> 214 validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
    215 if self is not validated_self:
    216     warnings.warn(
    217         'A custom validator is returning a value other than `self`.\n'
    218         "Returning anything other than `self` from a top level model validator isn't supported when validating via `__init__`.\n"
    219         'See the `model_validator` docs (https://docs.pydantic.dev/latest/concepts/validators/#model-validators) for more details.',
    220         stacklevel=2,
    221     )

ValidationError: 1 validation error for ChatMessage
blocks.1.image.url
  URL input should be a string or URL [type=url_type, input_value=None, input_type=NoneType]
    For further information visit https://errors.pydantic.dev/2.10/v/url_type

[dosubot]

Hey @malsaraa! I'm here to help you with any bugs, questions, or contributions. Let's dive into this issue and get it sorted!

To resolve the TypeError caused by the @field_validator for the url field in the ImageBlock model not handling None correctly, you can update the urlstr_to_anyurl method to check for None before processing the value. Here's the updated code:

@field_validator("url", mode="after")
@classmethod
def urlstr_to_anyurl(cls, url: str | AnyUrl | None) -> AnyUrl | None:
    """Store the url as Anyurl."""
    if url is None:
        return None
    if isinstance(url, AnyUrl):
        return url
    return AnyUrl(url=url)

This modification ensures that if the url is None, the method will return None without attempting to process it further, thus avoiding a TypeError ^[1].

To continue talking to Dosu, mention @dosu.

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[logan-markewich]

Feel free to make a PR @malsaraa -- I think you are correct.