If the pattern contains "[]" square brackets in it, no event was triggered in PatternMatchingEventHandler

[hariharan605]

Hello people,
I came across a strange issue. I'm using PatternMatchingEventHandler class to detect any changes occurring in a certain path.

If the pattern contains "[]" in it, no event was triggered. Please provide me any workaround or a solution on this.

Sample pattern : C:\Users\Test\AppData\Local\zwd\data\files\647971177\74j1a3a8020fba7934ecfb6579acd2de88c8c\[test].txt

Watchdog version : 0.9.0

Platform: Windows OS

[pree-dew]

I tried to reproduce the issue, I was able to reproduce this by using the underlying library (pathlib) used by PatternMatchingEventHandler.
pathlib library treat square bracket([]) as a pattern specified for allowing certain characters/letters etc. Ref: https://github.com/python/cpython/blob/003ba71dcbe94f0d5cb1d0c56d7f1d5a6dae56f7/Lib/fnmatch.py#L26

Adding an example:

>>> from pathlib import PurePosixPath
>>> PurePosixPath("a/b.py").match("[ab].py")
True
>>> PurePosixPath("a/a.py").match("[ab].py")
True
>>> PurePosixPath("a/ab.py").match("[ab].py")
False

Syntax of PurePosixPath: PurePosixPath(path).match(pattern)

As per that the pattern specified C:\Users\Test\AppData\Local\zwd\data\files\647971177\74j1a3a8020fba7934ecfb6579acd2de88c8c\[test].txt will trigger event for these scenarios:

C:\Users\Test\AppData\Local\zwd\data\files\647971177\74j1a3a8020fba7934ecfb6579acd2de88c8c\t.txt
C:\Users\Test\AppData\Local\zwd\data\files\647971177\74j1a3a8020fba7934ecfb6579acd2de88c8c\e.txt
C:\Users\Test\AppData\Local\zwd\data\files\647971177\74j1a3a8020fba7934ecfb6579acd2de88c8c\s.txt

Suggested Approach

• If the use case is that square bracket ([]) will be part of the filename then the following pattern can be used:

>>> from pathlib import PurePosixPath
>>> PurePosixPath("a/[ab].py").match("[[]ab[]].py")
True

• If the use case is that square bracket ([]) should match along with character matching functionality of pathlib then the following pattern can be used:

>>> from pathlib import PurePosixPath
>>> PurePosixPath("a/[a].py").match("[[][ab][]].py")
True
>>> PurePosixPath("a/[b].py").match("[[][ab][]].py")
True
>>> PurePosixPath("a/[ab].py").match("[[][ab][]].py")
False

Feel free to add details if there is a gap in understanding the use case.