reloader exlude_patterns behavior differs for WatchdogReloaderLoop and StatReloaderLoop

[robnagler]

Setting exclude_patterns to an absolute path, e.g. /home/me/bar/*, works fine with StatReloaderLoop, and fails to exclude paths with WatchdogReloaderLoop. The root cause is that WatchdogReloaderLoop uses watchdog which relies on pathlib.PurePath.match and StatReloaderLoop relies on `fnmatch. Here's a simple demonstration:

import fnmatch
assert fnmatch.fnmatch("/foo/bar/baz", "/foo/*")

import pathlib
assert pathlib.PurePosixPath("/foo/bar/baz").match("/foo/*"), "FAIL"

Pathlib's behavior is too strict for this particularly problem, since it matches from the right for relative paths and exact matches for absolute paths. fnmatch finds first match from the left.

The workaround is to disable the watchdog by passing reloader_type="stat" to run_simple.

Environment:

• Python version: 3.7.2
• Werkzeug version: 2.0.3

[davidism]

This sounds like a bug report for Watchdog, not Werkzeug. We don't appear to be calling PurePath.match in our reloader code, our code for exclude_patterns is the same between _find_stat_paths and _find_watchdog_paths, they both use fnmatch.

[robnagler]

You want to at least document the problem. It was tricky to track down.