[Pkg-rust-maintainers] Bug#1077846: rust-gdk4: autopkgtest regression: cannot find function `gdk_display_get_dmabuf_formats` in crate `ffi`

[Simon McVittie]

Source: rust-gdk4
Version: 0.8.2-6
Severity: serious
Justification: https://release.debian.org/testing/rc_policy.txt 6a
User: debian-ci at lists.debian.org
Usertags: needs-update

rust-gdk4 is failing tests on ci.debian.net, with lots of errors like:

343s error[E0425]: cannot find function `gdk_display_get_dmabuf_formats` in crate `ffi`
343s     --> src/auto/display.rs:129:33
343s      |
343s 129  |             from_glib_none(ffi::gdk_display_get_dmabuf_formats(self.as_ref().to_glib_none().0))
343s      |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: a function with a similar name exists: `gdk_display_get_default_seat`
343s      |
343s     ::: /usr/share/cargo/registry/gdk4-sys-0.8.2/src/lib.rs:4105:5

This is building against librust-gdk4-sys-dev 0.8.2-4 in the
autopkgtest environment. Does it perhaps need a versioned dependency on
librust-gdk4-sys-dev (>= 0.8.2-7) to get access to GTK 4.14.x features?

When testing a proposed migration, ci.debian.net takes all dependencies
from testing, unless a versioned dependency explicitly requires the
version from unstable. In this case the versioned dependency on GTK 4
means we get that from unstable:

 17s Get:167 http://deb.debian.org/debian unstable/main amd64 libgtk-4-common all 4.14.4+ds-8 [2,490 kB]
 17s Get:168 http://deb.debian.org/debian unstable/main amd64 libgtk-4-1 amd64 4.14.4+ds-8 [3,109 kB]
 18s Get:169 http://deb.debian.org/debian unstable/main amd64 gir1.2-gtk-4.0 amd64 4.14.4+ds-8 [212 kB]
 ...
 19s Get:298 http://deb.debian.org/debian unstable/main amd64 libgtk-4-dev amd64 4.14.4+ds-8 [981 kB]

and obviously we get the package under test from unstable, too:

 21s Get:425 http://deb.debian.org/debian unstable/main amd64 librust-gdk4-dev amd64 0.8.2-6 [72.5 kB]

but everything else comes from testing.

If a new gtk4 upload is needed for some other reason before this all
migrates, we might also want to give it a Breaks on
librust-gdk4-dev (<< 0.8.2-6~), librust-gdk4-sys-dev (<< 0.8.2-7~)
to stop the testing migration infrastructure from wasting its time
testing the new GTK against the old Rust bindings (which we already know
doesn't work).

    smcv