click.Path returns str, not pathlib.Path

[flying-sheep]

It’s surprising that INT returns an int, File a file, STRING a str, but Path a …str?

A click.Path parameter should return a pathlib.Path object.

[untitaker]

pathlib is Python 3 only afaict, Click isn't.

[untitaker]

FWIW I'm certain that an option to return a Path object is useful, but I can't see it becoming the default.

[flying-sheep]

it’s backported

[untitaker]

It's still not possible to make this a default since this would mean that the behavior of Click would depend on whether that backport is installed. And depending on that backport is not worth the added value.

[flying-sheep]

depending on that backport is not worth the added value.

what cost/value function evaluates to this result? :smile:

[untitaker]

In this case, new functionality. Pathlib is merely a new API for the same
thing.

Sorry, but I don't think this is going to happen. I'll gladly accept PRs for a
non-default option though.

On Mon, Aug 10, 2015 at 06:28:08AM -0700, Philipp A. wrote:

depending on that backport is not worth the added value.

what cost/value function evaluates to this result? :smile:

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[flying-sheep]

What do you mean with “non-default option”?

[untitaker]

Opt-in for returning a pathlib.Path object instead of a string. The user has to
depend on the pathlib library themselves unless it's in the stdlib. I think
that's doable.

On Mon, Aug 10, 2015 at 06:37:04AM -0700, Philipp A. wrote:

What do you mean with “non-default option”?

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[flying-sheep]

got it, makes sense. best would be to do it on arbitrary levels, right?

e.g. you could create a group that is configured to do it, passing it down to all subcommands and parameters, or on single parameters or even options.

the interaction of this with click.CommandCollection is obvious, but bad: merging a non-pathlib group with a pathlib group would simply behave as if each individual command would have been configured, and result in a mess, but that’s not really a problem i guess, and there’s no alternative anyway

[untitaker]

got it, makes sense. best would be to do it on arbitrary levels, right?

Honestly I don't think that's a good idea, it makes it hard to trace why a particular option is returning this particular type. If you want to avoid repetition/verbosity, you can still bind the created decorator to a new name for reuse, or create a new decorator that has it as default.

[flying-sheep]

hmm, yeah, using partial. only commands are defined on the group, so this would be easy.

[mitsuhiko]

Not going to happen. A custom path implementation might be something for addon packages.

[untitaker]

Welp-

[flying-sheep]

worth reevaluating in the light of PEP 519?

also are you going to sign the python 3 statement? if so, we can tackle this in 2020.

[untitaker]

That PEP makes a lot of things easier, but AFAICT it doesn't even apply to all
versions of Python 3.

I'd personally love to drop Python 2 at some point, but even for me 2020 is way
too soon. It's not (only) my decision to make.

On Mon, Jan 23, 2017 at 02:26:37AM -0800, Philipp A. wrote:

worth reevaluating in the light of PEP 519?

also are you going to sign the python statement? if so, we can tackle this in 2020.

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[flying-sheep]

i didn’t want to propose that, just ask 😉

the PEP partly applies to everything, as it describes a protocol, not just an API.

checking for the existence of __fspath__ works in any version!

[taion]

It would be really confusing to get a pathlib.Path object in 3.6+, but not in 3.5 or lower.

Is gating this on a (non-default) flag on click.Path still out per https://github.com/pallets/click/issues/405#issuecomment-140582568?

[mitsuhiko]

Since PATH does not exist anyways we can do two things. One is we set up a default mapping for pathlib.Path as input type (similar to how we have a default type for str) being passed to click.Path(convert=pathlib.Path) and then add support for convert being passed to click.Path.

That way someone can also pass it through something else that does something interesting with the path.

[altendky]

I understand finding time for reviews is hard but I wanted to make sure I didn't need to be doing something else for #405 #1148. I think it fits within the suggested approach of having a generic converter which a developer could pass pathlib.Path to if they so chose.

[altendky]

err, #1148

[NotTheEconomist]

I'd love to see this. I expected click.Path(path_type=pathlib.PurePath) would cast my result to a PurePath, but @altendky's converter is even more clear. Would love to see this pulled ASAP so I can start using it in my app.

[termim]

I 'd agree with @NotTheEconomist version without new arguments.
Please consider #1234 .

[jeremyh]

For the impatient, I defined my own like this. It accepts all the same options as click.Path:

class PathPath(click.Path):
    """A Click path argument that returns a pathlib Path, not a string"""
    def convert(self, value, param, ctx):
        return Path(super().convert(value, param, ctx))

@click.argument('input', type=PathPath(dir_okay=False))
def ...

(this usage style also feels cleaner to me than click.Path(...., converter=pathlib.Path), as well as more easily remembered. Path is built into Python's standard library and widely used, so I think it's worth a dedicated type.)

[adamtheturtle]

Thanks @jeremyh !

I have packaged this solution into https://pypi.org/project/click-pathlib, so you can use:

$ pip install click-pathlib

import click
import click_pathlib

@click.command('delete')
@click.argument(
    'existing_file',
    type=click_pathlib.Path(exists=True),
)
def delete(existing_file):
    existing_file.unlink()

[jrderuiter]

Seeing as Python 2 is now dead and all, does it maybe make sense to now transition to using pathlib.Path as a default instead of a str value?

[ThiefMaster]

Pretty sure that would require a major release, and while pathlib is awesome, I think it's the kind of change that would be a pain in the ass for any downstream user who doesn't already use pathlib.

[expobrain]

Also, even if Path is available on Python 3.x it's not mandatory to use it, a developer can still choose to use plain string or a Path instance

[untitaker]

Any request for making this the default basically asks for two things:

• New major version of click, break all existing code
• Drop Python 2 or pull in dependency on backport

Each of those points in isolation is an extreme measure to make this happen, combined even more.

[flying-sheep]

The second one isn’t, Python 2 isn’t supported anymore so you’re free to move on and get rid of all hideous compatibility hacks :tada:

About the first … click has a lot of major version releases, and derive from your reluctance that they’re all less intrusive than this one?

[untitaker]

Click supports Python 2.

[flying-sheep]

You know I mean that Python 2 is unmaintained as of 2 weeks ago. Supporting something that’s unmaintained is pretty futile.

[untitaker]

I'm saying that this is a completely separate decision to make. But I forgot that we already announced dropped support for Python 2 so this would probably be fine to land in Click 8.

https://palletsproject.com/blog/ending-python2-support/

[flying-sheep]

Hmm, just spitballing here, but maybe a transitional release could be done (after #1148 is merged). In Click 8, the following would raise a FutureWarning like this:

@click.argument('filename', type=click.Path())

You specified no Path converter. click.Path(converter=None) will result in a pathlib.Path object in Click 9. To avoid this warning, specify converter=str or converter=pathlib.Path.

And consequently, in Click 9 (or 10), the warning would be gone and the default changed.

[flying-sheep]

An alternative (also depending on #1148) would be to follow @mitsuhiko’s idea in https://github.com/pallets/click/issues/405#issuecomment-324987608:

We just add click.PATH and use it in examples instead of click.Path, therefore encouraging click.PATH without breaking changes. This would be less disruptive.