Running `jupyter notebook` opens visual studio code, not a browser

[yuvipanda]

If I run jupyter notebook, it pops up an empty instance of vscode for me - rather than a browser. I believe this is because .html files are opened in vscode on my system, rather than via the browser.

It took me a few tries to figure out why this was happening. We should maybe have better browser detection?

[bharathgs]

@yuvipanda is this resolved? if so what did you do?

[yuvipanda]

@bharathgs nope! I just run --no-browser now and copy the URL manually

[david-waterworth]

Same thing happened to me - I suspect vscode has been set as the default handler for html files and jupyter notebook uses the default association.

[jasongrout]

We use the python webbrowser module to pop up the browser. You can check with something like python -m webbrowser -t "http://www.python.org" (but perhaps with the notebook url instead).

You can also set the BROWSER environment variable for your command invocation, with something like:

BROWSER=/path/to/browser jupyter notebook

See https://docs.python.org/3.7/library/webbrowser.html

[yuvipanda]

@jasongrout 'python -m webbrowser -t "http://www.python.org"' loads in a browser, but python -m webbrowser -t "$(pwd)/a.html" opens in a text editor. I think this is the general problem.

I don't personally have a problem with setting browser environment, but this means the default experience for people who are told to run 'jupyter lab' on their terminal and a 'browser will pop up' is going to fail. That seems confusing and unideal.

[takluyver]

Gah, that's annoying. Which platform(s) are people seeing that on?

I had assumed webbrowser would always launch a browser, but it appears that it can delegate file:// URLs to the platform's native file handling. I don't know how to get around that. There are real security benefits to using the local file rather than launching the browser directly to http://localhost... with the security token.

[takluyver]

We can't launch the browser to an HTTP URL which then redirects to a file, because redirecting to file:// URLs is not allowed.

[yuvipanda]

@takluyver I'm on Ubuntu Linux

[bharathgs]

@takluyver platform:Ubuntu 18.10

[takluyver]

OK, I'm assuming that the webbrowser module is calling xdg-open, while is a wrapper around the desktop's open command (e.g. gio open ... on GNOME), and that calling that with a file:// URL is equivalent to calling it with a path, so it opens the .html file with the default handler.

Can you both check import webbrowser; webbrowser.get().name?

I haven't thought of any good way to avoid this, given that launching with file:// URL is a nice security improvement. Probably the best we can do is try to detect that the default browser is something like xdg-open and override the normal logic to find a browser. The downside is that we may launch the 'wrong' browser, not the default the user has configured in their system, in cases where we currently get the right one. But it should at least ensure that most users get a browser rather than an editor.

Of course, with problems like this it's always tempting to add a config option to 'do it the old way'. I'm trying to avoid that. Settings shouldn't make it too easy to remove security, because in a few years people will follow instructions they find to change the setting without understanding the implications. You can already solve this problem with configuration by setting e.g. c.NotebookApp.browser = 'firefox'. So it's only about how to handle the default, unconfigured case.

Any better ideas before I start trying to code a workaround?

[minrk]

I can reproduce this on mac if I associate html files with an editor (doesn't appear to be the default). Mac uses webbrowser.MacOSXOSAScript by default (no .name attr), which uses open, the equivalent of xdg-open.

I think discovering the default browser on all platforms is going to be a pretty big pain, but I can look into it on mac, at least.

[minrk]

Found the mac API for discovering the default browser and calling it via ctypes: https://nbviewer.jupyter.org/gist/minrk/0ea42a1d4bafde85c7699bac84d078a1

not sure if there's a better way.

[takluyver]

For Linux, the webbrowser module is already calling xdg-settings get default-web-browser to find a default; on my Fedora system, that makes it explicitly launches Firefox rather than xdg-open. But I guess for @yuvipanda and @bharathgs either the setting isn't set or the command to read it isn't available.

I was thinking of making a priority order on Linux something like this:

1. BROWSER environment variable
2. xdg-settings default browser
3. Firefox & variants like icecat
4. Chromium & variants
5. xdg-open

I don't know how many users would end up with a browser that's not their preferred default that way, but hopefully it's easy to configure your way out of that.

The situation on Mac seems more complex.