Interactive widgets should not output labels if label argument is an empty string

Summary

Since Streamlit 0.83, all the interactive widgets (except for streamlit.radio) outputs a <label> element for the widget even if the label value is an empty string. Before 0.83, setting a widget’s label to an empty string left out the <label> element.

The current behaviour results in unwanted vertical whitespace before a widget for empty labels.

Steps to reproduce

Code snippet:

import streamlit as st

for widget in (st.text_input, st.number_input, st.date_input, st.time_input, st.slider, st.color_picker, st.text_area):
    st.subheader(widget.__name__)
    c1, c2 = st.beta_columns(2)
    with c1:
        widget("Label")
    with c2:
        widget("")

for widget in (st.selectbox, st.radio, st.multiselect, st.select_slider):
    st.subheader(widget.__name__)
    c1, c2 = st.beta_columns(2)
    with c1:
        widget("Label", ["A", "B", "C"])
    with c2:
        widget("", ["A", "B", "C"])

The code snippet shows the differences for all the interactive widget. But, here’s a select screenshot showing the differences between 0.82 and 0.84 for streamlit.selectbox and streamlit.radio. In Streamlit 0.84, only streamlit.radio works the same as before. Everything else outputs empty <label> elements.

Streamlit 0.82:

Streamlit 0.84:

Expected behavior:

All the widgets should omit outputting labels if the label argument is an empty string.

Actual behavior:

The streamlit.radio widget is the only one that does not output empty labels.

Is this a regression?

The current behaviour was introduced in Streamlit 0.83.

Debug info

• Streamlit version: Streamlit, version 0.84.2
• Python version: Python 3.8.11
• Using Conda? PipEnv? PyEnv? Pex? Just pip
• OS version: Debian buster (in a python:3.8 container)
• Browser version: Safari 14.1 on macOS Mojave 10.14.6

Additional information

None.

[kinghuang]

The issue’s a bit complicated, because it seems the empty <label> elements were intentionally added in #3317, in response to #3220. That PR optimizes for alignment across columns, but reverses past behaviour and gets in the way for other layouts.

I’m hiding the empty labels for now with a bit of css.

label:empty { display: none }

[kajarenc]

Hey, this is fixed now with the label_visibility param, that we add for all widgets with labels.

We encourage to always use a meaningful labels for accessibility reasons

But now you can use keyword argument label_visibility="hidden" to hide label or label_visibility="collapsed" to collapse whitespace completely.

This feature will be available on streamlit 1.13.0 (or you can use it now with streamlit-nightly