Filechooser on mac: using path, crashes python

[ElliotGarbus]

MacOS 10.14.6

using the path parameter causes python to crash (not just the app).
Using the use_extensions with path causes an uncaught exception.

Test case:

from pathlib import Path

from kivy.app import App
from kivy.lang.builder import Builder
from plyer import filechooser

kv = '''
BoxLayout:
    orientation: 'vertical'
    Button:
        text: 'Test: Open, filters=["*.pdf"]; this will crash python'
        on_release: app.ft.open(filters=['*.pdf'])
    Button:
        text: 'Test: Open, filters=["*.pdf"] use_extensions=True; throws exception '
        on_release: app.ft.open(filters=['*.pdf'], use_extensions=True)
    Button:
        text: 'Test: Open, filters=[] this will work as expected'
        on_release: app.ft.open()
    Label:
        text: 'plyer.filechooser.open_file() with a filter will crash on mac'
'''


class FileTest:
    def __init__(self):
        self.file_name = ''

    def open(self, **kwargs):
        filechooser.open_file(title='Open Patch File',
                              on_selection=self._open_selection, **kwargs)

    def _open_selection(self, selection):
        try:
            self.file_name = Path(selection[0]).name
        except (ValueError, IndexError):  # The user did not select a file
            print('open canceled')
        else:
            print(f'open file: {self.file_name}')


class PlyerFilechooserTestApp(App):
    ft = FileTest()

    def build(self):
        return Builder.load_string(kv)


if __name__ == '__main__':
    PlyerFilechooserTestApp().run()

[matham]

I ran into this issue, where if I specified filers it would crash.

[Mulugruntz]

Same here.

This crashes here:
https://github.com/kivy/plyer/blob/11b6b4b/plyer/platforms/macosx/filechooser.py#L96

2020-06-30 22:21:01.316 python[92472:38636130] -[__NSSingleObjectArrayI _getCString:maxLength:encoding:]: unrecognized selector sent to instance 0x7fbbf1f74820
2020-06-30 22:21:01.335 python[92472:38636130] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSSingleObjectArrayI _getCString:maxLength:encoding:]: unrecognized selector sent to instance 0x7fbbf1f74820'
*** First throw call stack:
(
	0   CoreFoundation                      0x00007fff4c94dcfd __exceptionPreprocess + 256
	1   libobjc.A.dylib                     0x00007fff76ff3a17 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff4c9c7b06 -[NSObject(NSObject) __retain_OA] + 0
	3   CoreFoundation                      0x00007fff4c8efb8f ___forwarding___ + 1485
	4   CoreFoundation                      0x00007fff4c8ef538 _CF_forwarding_prep_0 + 120
	5   CoreFoundation                      0x00007fff4c86611c CFStringGetCString + 140
	6   Foundation                          0x00007fff4ebb9d1f NSHFSTypeCodeFromFileType + 45
	7   AppKit                              0x00007fff4a673bc2 -[NSSavePanel _setEnabledFileTypes:] + 317
	8   AppKit                              0x00007fff4a673847 -[NSSavePanel setAllowedFileTypes:] + 400
	9   libffi.dylib                        0x00007fff7636af6c ffi_call_unix64 + 76
	10  ???                                 0x00007fbbf42d1570 0x0 + 140445232207216
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Please note that I believe there's another bug on line 90 and 92 where it uses f.strip() when it made sure beforehand that it wouldn't be a string. The expected behaviour would be to use the _ variable from line 88 (but renamed) to perform the .strip() on.

If this bug is fixed, it will still not fix the NSException from above.

[Mulugruntz]

The weird thing is that it's an NSOpenPanel but the throw call stack mentions NSSavePanel. I'll dig into that direction.

[matham]

If you figure it out a PR is always welcome!

[Mulugruntz]

I'm still digging but it's likely to be an issue on https://github.com/kivy/pyobjus or even below... :-/
And I'm not well-versed in Cython.

I tried both with
pipenv install -e "git+https://github.com/kivy/pyobjus.git@672ed61#egg=pyobjus"
and
pipenv install pyobjus==1.1.0

and the result is exactly the same.

So I'd imagine it has not been fixed yet.

[Mulugruntz]

This minimal code reproduces the crash:

from pyobjus import autoclass, objc_arr, objc_str
from pyobjus.dylib_manager import load_framework, INCLUDE

load_framework(INCLUDE.AppKit)

NSOpenPanel = autoclass('NSOpenPanel')
panel = NSOpenPanel.openPanel()

ftypes_arr = objc_arr([objc_str('jpg')])
panel.setAllowedFileTypes_(ftypes_arr)

If I do a print(panel), I get <__main__.NSKVONotifying_NSOpenPanel object at 0x116b6e450> which shows it's an NSOpenPanel. Even though it seems to be bound to the NSSavePanel implementation underneath.

[Mulugruntz]

Found the issue!
I'll do a PR.

[Mulugruntz]

The thing was that objc_arr was expecting positional arguments.
https://github.com/kivy/pyobjus/blob/3f6314152ea850bff8a218fb3dbc4df22431a4f2/pyobjus/pyobjus_types.pxi#L371

And the list was given as an argument.
In Objective-C, there's this thing where when you initialize with a list, the last element must have nil. And objc_arr is adding a None at the end of the positional arguments.

So, instead of having ('jpg', 'JPG', None), it had (['jpg', 'JPG'], None).
The setAllowedFileTypes() method was expecting to work on strings and received a list. Crash.