webbrowser.open with file: URLs may launch editor instead of browser

Bug report

Transferred to https://discuss.python.org/t/support-for-file-urls-in-webbrowser-open/81612 until consensus is reached.

Bug description:

In the code:

import webbrowser
from pathlib import Path

index_html = Path.cwd() / "index.html"
webbrowser.open(index_html.as_uri())

It is common for xdg-open (on linux) or open location (on mac) or os.startfile (on windows) to be selected as the default browser. This is great and simple for http[s] urls, but when these are passed file:// urls, all of the above select the default opener for HTML files, which may not be a browser at all (commonly a text editor for developer systems).

I don't know if there's a way to indicate that Browser entries can handle given URL schemes, but when selecting a browser from the try list, ideally these generic 'open' mechanisms should be skipped for file: URLs. Even better, use standard APIs to lookup the default browsers for http[s] and invoke that explicitly, rather than relying on an interpretation of "open URL" which is only valid for http URLs.

I believe URLForApplicationToOpenURL is the current macOS API to look up the application for http:, which could be used to launch explicitly with a browser. I guess xdg-settings get is already the equivalent for most linux situations and preferred if available, which is great. I'm not sure there's a more general way to discover what xdg-open will do with http://, but we have occasional reports where xdg-settings get default-web-browser doesn't work and xdg-open is invoked and doesn't launch a browser (or launches a different browser). I've no idea what the Windows call would be, but this looks like the same question.

This appears to have been opened long ago as #37540 and erroneously closed as an Apple bug (all platforms exhibit this behavior, and I think the bug is pretty clearly in webbrowser's assumption that "open file://path.html" means "open file://path.html with a web browser" which does not appear to be what any of the platforms mean by the chosen API).

CPython versions tested on:

3.9, 3.10, 3.11, 3.12

Operating systems tested on:

Linux, macOS, Windows

Linked PRs

• gh-130031
• gh-130535
• gh-130538
• gh-130541

阅读报告中链接的 Linux xdg-open、Windows os.startfile 和 macOS open 位置实现所在的 Lib/webbrowser.py。先查看转移过来的讨论和链接的 PR，因为共识和拟议的工作在其他地方。需要就 file: URL 的跨平台行为达成一致，并完成相应的测试，才算完成。