I don't think this is entirely right. Are you sure about the /usr/lib | %{_libdir} change at the bottom of the diff? IIRC, the issue was that the package was dropping this file in /usr/lib regardless of what libdir was...

Hmm perhaps flatpak-module has changed some values but without that removal line it's complaining about unpackaged file.

Hmm the built results are .... interesting.
/me scratching his head..

So I've made some changes that seem to work both for flatpak and fedora https://koji.fedoraproject.org/koji/taskinfo?taskID=82746385

I would appreciate if you could have a look when you get a chance.

This is still not quite right, but I understand where you are trying to go. I just committed a change to rawhide that does the right things (I think), please check that and let me know if it resolves the flatpak build issues.

Hmm I must say I'm quite confused about this now...

Checking for unpackaged file(s): /usr/lib/rpm/check-files /builddir/build/BUILDROOT/fuse3-3.10.5-3.module+f35+2+99ac73cd.x86_64
error: Installed (but unpackaged) file(s) found:
   /usr/lib/udev/rules.d/99-fuse3.rules
RPM build errors:
    Installed (but unpackaged) file(s) found:
   /usr/lib/udev/rules.d/99-fuse3.rules
Child return code was: 1
EXCEPTION: [Error()]
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/mockbuild/trace_decorator.py", line 93, in trace
    result = func(*args, **kw)
  File "/usr/lib/python3.9/site-packages/mockbuild/util.py", line 600, in do_with_status
    raise exception.Error("Command failed: \n # %s\n%s" % (command, output), child.returncode)
mockbuild.exception.Error: Command failed: 
 # /usr/bin/systemd-nspawn -q -M 79b3e3a675e143e0bbca6e610ba90927 -D /var/lib/mock/module-gnome-boxes-main-3520220217011430-1/root -a -u mockbuild --capability=cap_ipc_lock --bind=/tmp/mock-resolv.xrxu3_it:/etc/resolv.conf --bind=/dev/btrfs-control --bind=/dev/loop-control --bind=/dev/loop0 --bind=/dev/loop1 --bind=/dev/loop2 --bind=/dev/loop3 --bind=/dev/loop4 --bind=/dev/loop5 --bind=/dev/loop6 --bind=/dev/loop7 --bind=/dev/loop8 --bind=/dev/loop9 --bind=/dev/loop10 --bind=/dev/loop11 --console=pipe --setenv=TERM=vt100 --setenv=SHELL=/bin/bash --setenv=HOME=/builddir --setenv=HOSTNAME=mock --setenv=PATH=/usr/bin:/bin:/usr/sbin:/sbin --setenv=PROMPT_COMMAND=printf "\033]0;<mock-chroot>\007" --setenv=PS1=<mock-chroot> \s-\v\$  --setenv=LANG=C.UTF-8 --resolv-conf=off bash --login -c /usr/bin/rpmbuild -bb --target x86_64 --nodeps /builddir/build/SPECS/fuse3.spec

This is the error I'm getting from flatpak build. It seems to be ignoring the udevrulesdir ?

Full log: https://gist.githubusercontent.com/JayDoubleu/db2613037aedc3306f7a80325234f0b4/raw/f9d84111f38b9ec866e436c9ad4e89eeb1f6d58d/fuse3-build.log

I think it is not matching the condition so it's building with just %meson instead of the one with specific udevrulesdir directly ?

https://github.com/libfuse/libfuse/blob/bdd2d4110fbc6d2059eb699efad2cca4a7eacccb/util/meson.build#L26

When I just change your commit to :

%build
export LC_ALL=en_US.UTF-8
%if ! 0%{?_vpath_srcdir:1}
%global _vpath_srcdir .
%endif
%if ! 0%{?_vpath_builddir:1}
%global _vpath_builddir build
%endif
%if 0%{?el6}
%if ! 0%{?__global_ldflags:1}
%global __global_ldflags ""
%endif
%meson -D udevrulesdir=%{_udevrulesdir}
%else
%if 0%{?flatpak}
%meson -D udevrulesdir=%{_udevrulesdir}
%else
%meson
%endif
%endif

It builds fine.

Closing this out. Reopen if still needed.