Summary

If you name, for example, two buttons 'abc', you will get some weird behavior (see below).

To avoid this, we should ensure that no two widgets have the same name by raising an exception should the user violate this rule.

Steps to reproduce

Run the following code:

import streamlit as st

if st.button('abc'):
    st.success('First button fired.')
if st.button('abc'):
    st.success('Second button fired.')

Behavior

Actual behavior

The button appears twice (no exceptions thrown):

and when you click the button, it fires twice:

Expected behavior

The second button named 'abc' should raise an exception.

Is this a regression?

Not sure.

Debug info

$ streamlit version && python --version && pyenv --version && sw_vers && "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" --version

Streamlit, version 0.45.0
Python 3.6.5
pyenv 1.2.3
ProductName:	Mac OS X
ProductVersion:	10.14.6
BuildVersion:	18G84
Google Chrome 76.0.3809.132