Multiple options passed via environment variables are split by character

[sampsyo]

An option with multiple=True yields unexpected (i.e., not useful) behavior when it is specified via an environment variable.

Here's a simple example script:

import click

@click.command()
@click.option('--arg', multiple=True)
def cmd(arg):
    print(arg)

if __name__ == '__main__':
    cmd(auto_envvar_prefix='TEST')

It works as expected when arg is specified with an ordinary command-line option:

$ python3 test.py --arg foo
('foo',)

But when we use an environment variable instead, Click splits the string into characters:

$ TEST_ARG=foo python3 test.py
('f', 'o', 'o')

This is the classic Python iterating-over-a-string-when-you-thought-you-had-a-list failure mode. (These examples were run with click 0.7 from PyPI.)

I can see two reasonable resolutions here: split environment variables on whitespace or don't split them at all. The latter is probably more predictable but the former is more flexible.

[mitsuhiko]

I found a nice way to handle this now. It's the type's responsibility to provide a way to customize this. This means that I can have "foo:bar:baz" for paths and files and "foo bar baz" for everything else. This can also be further customized to even fully disable that feature.

Thanks for bringing it up.

[sampsyo]

Fantastic; this seems like the perfect solution.

Thanks for click! ✨