Fixing Plotly Chart Deprecation Warnings In Streamlit

Hey there, fellow Streamlit enthusiasts! Have you ever been happily building your interactive dashboards, dropping in some beautiful Plotly charts, only to be greeted by a rather stern-looking deprecation warning? You’re not alone! It seems like a recent update has made the st.plotly_chart function a bit more particular about how we pass arguments, specifically around kwargs. Even when you’re just trying to set the width or height of your chart using the documented "content" value, Streamlit might throw a fit. This can be super confusing, especially when you're not intentionally using variable keyword arguments. Let's dive deep into why this is happening and how we can navigate this little hiccup to keep our Streamlit apps running smoothly and warning-free.

Understanding the kwargs Deprecation Warning

So, what exactly is this kwargs deprecation warning all about? In Python, **kwargs is a special syntax that allows a function to accept an arbitrary number of keyword arguments. These arguments are then collected into a dictionary. Streamlit, in its quest to provide a cleaner and more predictable API, has decided to deprecate the direct use of arbitrary keyword arguments for st.plotly_chart. The idea is that users should stick to the explicitly defined parameters like use_container_width (now width and height) and the config argument for any Plotly-specific configurations. The warning is triggered when the function detects that there are any remaining keyword arguments after it has processed all its expected parameters. This is a good thing in principle, as it encourages developers to use the API as intended and avoid potential conflicts or misunderstandings. However, in this specific case, it seems to be misfiring. It's flagging a warning even when users are providing arguments that are supposed to be valid, like width="content", which is a documented and intended way to make your chart responsive to its container. This suggests a potential issue in how Streamlit is parsing or handling these specific arguments, possibly misinterpreting them as general kwargs rather than recognized parameters.

The recent changes, likely introduced in Streamlit versions around 1.50.0, aim to guide users towards a more robust way of passing configurations to Plotly charts. Previously, you might have been able to pass a variety of arguments directly, and Plotly would interpret them. However, as libraries evolve, so do their APIs. Streamlit's st.plotly_chart function has specific parameters it expects. When you pass an argument that isn't one of these expected parameters, and it's not part of a designated configuration object, Streamlit flags it. The warning message explicitly states: “Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future release. Use the config argument instead to specify Plotly configuration options.” The confusion arises because width="content" is a valid and documented way to control the chart's behavior, and it should ideally be handled by the st.plotly_chart function itself, not bundled into a general kwargs warning. This implies that either the function isn't recognizing "content" as a special value for width/height, or the internal logic that checks for leftover kwargs is too broad and catches this valid parameter incorrectly. This is a classic example of how seemingly small changes in API design can have ripple effects, and it’s crucial for library maintainers to ensure backward compatibility or provide clear migration paths. For users, it means we need to be aware of these shifts and adapt our code accordingly, while also providing feedback when we encounter unexpected behavior like this.

Reproducing the kwargs Warning with Code

To really understand the issue, let's look at a simple, reproducible code example. This is exactly what was provided in the issue report, and it clearly demonstrates the problem:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360)

st.plotly_chart(fig, width="content")

When you run this code in a Streamlit application (specifically with versions like 1.50.0 and potentially others around that release), you'll likely see the deprecation warning appear in your console or directly in the app output. The warning itself usually looks something like this: “Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future release. Use the config argument instead to specify Plotly configuration options.” It's fascinating because we are not passing any arbitrary, unexpected keyword arguments here. We're using width="content", which is intended to make the Plotly chart responsive to the width of its container in Streamlit. This is a common and useful pattern for ensuring charts look good on different screen sizes without hardcoding pixel values. The fact that this perfectly valid and documented parameter triggers the kwargs warning suggests that Streamlit's internal argument parsing might be treating width="content" as an unrecognized keyword argument, rather than as a specific instruction for the plotly_chart function. This is a critical point: the warning is meant for truly variable, potentially problematic keyword arguments, not for standard, documented features of the component.

This behavior can be particularly frustrating because it deviates from the expected outcome. The documentation for st.plotly_chart and related Streamlit features suggests that using width="content" (or use_container_width=True in older versions, which width="content" is meant to replace or complement) is the correct way to achieve responsive charts. Therefore, encountering a deprecation warning for using a documented feature implies a potential bug or a misunderstanding in how the Streamlit component is implemented or how it interprets its own arguments. It’s a regression because, in previous versions, this specific usage likely did not trigger such a warning, allowing developers to seamlessly integrate responsive Plotly charts. The implication is that the logic responsible for checking for deprecated or unused keyword arguments might be too aggressive or not correctly distinguishing between generic kwargs and specific, valid parameters that were potentially renamed or re-purposed.

Why is this a Regression?**

This issue is indeed a regression, meaning it worked correctly in a previous version of Streamlit and is now broken. This is often the most frustrating type of bug for users because it disrupts existing workflows and codebases that were previously stable. In earlier versions of Streamlit, you could typically use parameters like width="content" or use_container_width=True with st.plotly_chart without encountering any kwargs deprecation warnings. This functionality was crucial for creating dynamic and responsive web applications, where charts need to adapt their size based on the user's screen resolution or the layout of the Streamlit dashboard. The introduction of the kwargs check, while well-intentioned to clean up the API and guide developers towards using the config parameter for Plotly-specific settings, has inadvertently caught valid parameters in its net.

When a feature that was previously functional suddenly stops working or starts issuing warnings, it signals a change in the library's behavior that wasn't smoothly handled. This can occur for several reasons: the implementation of the kwargs check might have become overly broad, failing to recognize arguments that are explicitly handled by Streamlit's plotly_chart wrapper. Alternatively, the way width="content" is processed internally might have changed, causing it to be categorized as an arbitrary keyword argument rather than a specific display setting. This kind of regression breaks the principle of least surprise for developers. They rely on the stability and documented behavior of libraries. When a warning appears for a standard use case, it forces developers to spend time debugging their own code, only to find that the issue lies within the library itself. This not only wastes valuable development time but can also erode confidence in the library's stability. Identifying this as a regression is key to prioritizing its fix, as it directly impacts users who were successfully using this feature before the change.

The core of the problem lies in the implementation of the warning system. It seems to be a blanket check for any keyword arguments that are not explicitly handled by Streamlit's core plotly_chart function signature. However, parameters like width (when set to `