Default float fields not updated when model instance argument changed

[benoitsdm]

Checklist

• I have searched the existing issues for similar issues.
• I added a very descriptive title to this issue.
• I have provided sufficient information below to help reproduce this issue.

Summary

Thanks for the great library, really powerful !

I have noticed a bug that you can reproduce with the minimalist example.

Reproducible Code Example

import streamlit as st
import streamlit_pydantic as sp
from pydantic import BaseModel

class Model(BaseModel):
    i: int
    s: str

a= Model(i=1, s="1")
b= Model(i=2, s="2")

init = st.selectbox(label="instance", options=[a, b])

data = sp.pydantic_form(key="f", model=init)

if data:
    st.json(data)

Steps To Reproduce

When you change the init model from the select box, the string default is successfully updated but not the int.

Expected Behavior

No response

Current Behavior

No response

Is this a regression?

• Yes, this used to work in a previous version.

Debug info

• streamlit-pydantic version= { git = "https://github.com/lukasmasuch/streamlit-pydantic", branch = "main" }
• Python version: 3.12.5

Additional Information

Not sure how the session state this handled under the hood, do you have any quick work around ? Or if you have any idea where the bug can come from, please points me the function I can have a look.

[benoitsdm]

    if key not in ["FormSubmitter:f-Submit", "run_id"]:
        del st.session_state[key]

seems to fix the bug but i am not sure if it's dangerous and can have side effect ?

I guess it's an issue with _render_single_number_input but still trying to understand how it works

[benoitsdm]

After digging a bit, it is due to these lines:

if self._session_state.get(streamlit_kwargs["key"]) is None:
        if property.get("init_value") is not None:
            streamlit_kwargs["value"] = number_transform(property["init_value"])
        elif property.get("default") is not None:
            streamlit_kwargs["value"] = number_transform(property["default"])  # type: ignore
        else:
            if "min_value" in streamlit_kwargs:
                streamlit_kwargs["value"] = streamlit_kwargs["min_value"]
            elif number_transform == int:
                streamlit_kwargs["value"] = 0
            else:
                # Set default value to step
                streamlit_kwargs["value"] = number_transform(
                    streamlit_kwargs["step"]
                )
else:
        streamlit_kwargs["value"] = number_transform(
        self._session_state[streamlit_kwargs["key"]]
        )

Not sure if it's made on purpose or not, if there is already a value in session_state, we use it instead of using property["init_value"]. Nothing similar in _render_single_string_input. If you confirm it's a bug i can submit a PR