`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

まずリンクされた PR gh-149255 を確認し、次にエントリーポイント webbrowser.open と BROWSER 環境変数の処理を調べます。Linux 上で Firefox を設定した状態で提供されたスクリプトを再現し、設定したブラウザーの起動がすぐに戻り、Ctrl+C でクラッシュせず、ターミナルブラウザーについても適切なカバレッジがあることを確認できたら、issue は完了とします。