[Bug]: "default" argument in Field not respected for FunctionTool

[lucasvw]

Bug Description

When creating a FunctionTool and using the Pydantic Field object to specify the "default" value, the default value is not set when calling the function. Somehow the type of the argument is pydantic.fields.FieldInfo

Version

lama-index 0.12.5

Steps to Reproduce

from pydantic import Field
from llama_index.core.tools import FunctionTool
from typing import Optional


def get_weather(
    location: Optional[str] = Field(
        default="Berlin"
    ),
) -> str:
    """Usfeful for getting the weather for a given location."""
    if location == "Berlin":
        return "nice weather in Berlin"
    return "bad weather!"


tool = FunctionTool.from_defaults(get_weather)

> tool().content
'bad weather!'

> tool("Berlin").content
'nice weather in Berlin'

Relevant Logs/Tracbacks

This fixes it by the way:

from pydantic import Field
from pydantic.fields import FieldInfo
from llama_index.core.tools import FunctionTool
from typing import Optional


def get_weather(
    location: Optional[str] = Field(
        default="Berlin"
    ),
) -> str:
    """Usfeful for getting the weather for a given location."""
    if isinstance(location, FieldInfo):
        location = location.get_default()
    if location == "Berlin":
        return "nice weather in Berlin"
    return "bad weather!"


tool = FunctionTool.from_defaults(get_weather)

[dosubot]

Hey @lucasvw! I'm here to help you with any bugs, questions, or contributions. Let's get this sorted out!

The issue you're encountering with the "default" argument in the Pydantic Field not being respected when creating a FunctionTool in version 0.12.5 of LlamaIndex is due to the from_defaults method of the FunctionTool class. This method explicitly removes FieldInfo defaults from the function signature. The code iterates over the parameters of the function signature and replaces any default value that is an instance of FieldInfo with inspect.Parameter.empty, effectively removing the default value ^[1].

To work around this, you might consider setting default values directly in the function signature without using Pydantic's Field, or handle defaults within the function logic itself.

To continue talking to Dosu, mention @dosu.

---

^{Help Dosu learn! Give it feedback: Great Response | Irrelevant Answer | Incorrect Sources | Too Verbose | Hallucination | Other}

[vincentWuK]

same

[PhilKlae]

Very good explanation your answer helped me a lot! I had a case where I needed a FunctionTool instance with some code driven parameters, and the agent was supposed to only see and use one of those arguments and manipulate it. The situation was especially spicy for some other reasons but maybe this helps somebody in a similar situation:

Function definition looks like this
async def process_agent_tool(fn_get_tools, agent_config, input = "Fetch object with id xxx create instance of xxx") -> str:

Then I need to inject my code driven parameters into it but keep it callable so I used partial trick
func = partial(agent_tool.process_agent_tool,create_tools_for_sub_agent, tool_config.agent_id)
Then I could create the callable tool like this
tool_instance = FunctionTool.from_defaults( fn=func, name=tool_config.name, description=tool_config.description )

Hey @lucasvw! I'm here to help you with any bugs, questions, or contributions. Let's get this sorted out!

The issue you're encountering with the "default" argument in the Pydantic Field not being respected when creating a FunctionTool in version 0.12.5 of LlamaIndex is due to the from_defaults method of the FunctionTool class. This method explicitly removes FieldInfo defaults from the function signature. The code iterates over the parameters of the function signature and replaces any default value that is an instance of FieldInfo with inspect.Parameter.empty, effectively removing the default value [1].

To work around this, you might consider setting default values directly in the function signature without using Pydantic's Field, or handle defaults within the function logic itself.

To continue talking to Dosu, mention @dosu.

Help Dosu learn! Give it feedback: Great Response | Irrelevant Answer | Incorrect Sources | Too Verbose | Hallucination | Other

[PhilKlae]

Now that I understood the FunctionTool.from_defaults method the name makes sense. Yet I didn't find good documentation about this, but it may be my bad. I could also add documentation since this is open source, but im not sure where to start

[Br1an67]

I'd like to work on this. The fix extracts actual default values from FieldInfo objects during FunctionTool.__init__ and applies them as lowest-priority defaults in call()/acall(), so Field(default=...) values are properly used when arguments aren't provided.

PR: #20839