I'm running an opensuse 15.1 inside windows subsystem for linux, and I found
that upgrading the filesystem to WslFs breaks zypper.

if you run "wsl --upgrade openSUSE-Leap-15-1" as Administrator on windows, and
afterwards try to run "zypper refresh" in your WSL Leap image, zypper fails
with these errors:
kirika:~ # zypper ref
Retrieving repository 'leap-15.1' metadata
.............................................................................................................................................................[error]
Repository 'leap-15.1' is invalid.
[leap-15.1|http://download.opensuse.org/distribution/leap/15.1/repo/oss/] Valid
metadata not found at specified URL
Please check if the URIs defined for this repository are pointing to a valid
repository.
Skipping repository 'leap-15.1' because of the above error.
Retrieving repository 'leap-15.1-update' metadata
......................................................................................................................................................[error]
Repository 'leap-15.1-update' is invalid.
[leap-15.1-update|http://download.opensuse.org/update/leap/15.1/oss/] Valid
metadata not found at specified URL
Please check if the URIs defined for this repository are pointing to a valid
repository.
Skipping repository 'leap-15.1-update' because of the above error.
Could not refresh the repositories because of errors.


in /var/log/zypper.log you see:

2019-12-13 12:02:20 <5> kirika(120) [zypp] Exception.cc(log):166
RepoManager.cc(refreshMetadata):1221 THROW:   
[leap-15.1-update|http://download.opensuse.org/update/leap/15.1/oss/] Valid
metadata not found at specified URL
2019-12-13 12:02:20 <5> kirika(120) [zypp] Exception.cc(log):166 History:
2019-12-13 12:02:20 <5> kirika(120) [zypp] Exception.cc(log):166  - Can't copy
public key data from
/var/cache/zypp/raw/leap-15.1-updatekRrguZ/repodata/repomd.xml.key to
/var/tmp/TmpFile.DWnK2Z
2019-12-13 12:02:20 <5> kirika(120) [zypp] Exception.cc(log):166
2


which leads me to believe that WslFS as storage for a WSL image is incompatible
with zypper.

There is no workaround, and only a **destructive** fix: reset the "app" which
basically means wipe the image and set it up again, losing everything you did
inside.
or run openSUSE-Leap-15-1.exe clean in an administrator shell which is
basically the same, and also wipes everything.

Reproduces with 15.0 and 15.1, can't try with other versions since they aren't
on the windows store.