`webbrowser.open` hangs indefinitely when exiting browser defined in `BROWSER` environment variable

Bug report

Bug description:

To reproduce

On my system, I have set the BROWSER environment variable to suggest a preferred browser for console applications to use.

# my .zshrc
# Use Firefox Dev Edition as my preferred browser if it's on the path
if command -pv firefox-aurora &> /dev/null; then
    export BROWSER='firefox-aurora'
elif command -pv firefox &> /dev/null; then
    export BROWSER='firefox'
fi

As a consequence, calls to webbrowser.open launch Firefox Deverloper Edition (firefox-aurora), which is correct. However, if an instance of firefox-aurora isn't already running, my script will freeze until firefox-aurora exits entirely.

import webbrowser

webbrowser.open('https://example.com')
print('Done')

Additionally, interrupting my script using Ctrl+C causes the browser to crash, likely due to a SIGHUP.

This causes significant issues for my script, as I wish to open multiple sites at once.

Suggested fix

The browser defined by the BROWSER variable should be disowned by the webbrowser , perhaps by making it a UnixBrowser rather than a GenericBrowser. This does risk breaking terminal-based browsers, so I wonder if there's a way to determine if the browser is terminal-based so that we can tell whether to p.wait() or not.

Otherwise, do you believe this may be an issue with Firefox instead, in that they should launch and detach a new process, allowing the process launched through Python to exit immediately?

One more possibility is that the BROWSER variable is intended for terminal-based browsers, similarly to the EDITOR variable for terminal editors and the VISUAL variable for graphical editors.

CPython versions tested on:

3.12

Operating systems tested on:

Linux (specifically, Fedora 40)

Linked PRs

• gh-149255

Inizia esaminando la PR collegata gh-149255, quindi analizza l’entry point webbrowser.open e la gestione della variabile d’ambiente BROWSER. Riproduci lo script fornito su Linux con Firefox configurato e considera completata la issue quando l’avvio del browser configurato restituisce prontamente il controllo senza che Ctrl+C provochi un crash, con una copertura adeguata per i browser da terminale.