Packaging a GNOME rust application

Introduction

GNOME increasingly uses Rust as language for libraries (e.g. rsvg) and a growing number of GUI programs (e.g. Shortwave). Most of the GUI programs use meson as build system. This page tries to give an introduction how you should package such a program. Note: this explicitly is targeted for programs either endorsed by GNOME or using the GTK-rs bindings. It also works for other programs and libraries (see python-cryptography) though you might need to make adjustments. This is explicitly not intended for crates or binary crates, for those see Teams/RustPackaging.

Packaging

First you should check if the program you're trying to introduce compiles with the current gtk-rs stack in debian. For instance if the program uses gtk-rs 0.7.x but the current debian one is 0.6.x you can get the source and "downgrade" all affected crates in Cargo.toml , then run cargo build to see if it compiles. Updating the gtk-rs stack involves >44 crates to build and upload one by one so maybe you're in luck if it works with an older version. Additionally, install and run cargo-debstatus on the cloned repo to check if all other dependencies are in debian. If both prerequisites are satisfied you need to "translate" the dependencies from Cargo.toml to build-dependencies in debian/control .

Then you can get the source and prepare the DEP-14 repo as usual.

Mapping rust dependencies to build-dependencies

For instance adw = {package = "libadwaita", version = "0.4", features = ["v1_3"]} translates to librust-libadwaita+v1_3-dev (>= 0.4). To automate this procedure you can build debcargo from this MR and run debcargo deb-dependecies Cargo.toml in the project root. This does not work yet for alpha, beta and rc version as dependencies and workspaces are not yet supported, too. If you have a dependency in Cargo.toml referencing a git url (e.g. rustdoc-stripper = { git = "https://github.com/GuillaumeGomez/rustdoc-stripper" } replace it with the librust-* debian equivalent in debian/control and patch Cargo.toml with quilt to use a versioned dependency (and hope it compiles). If not, open an issue upstream. librsvg also might get included that way, in that case just add librsvg2-dev as build-dependency in debian/control and you should be good to go.

Add cargo to call the cargo wrapper (and meson if the program uses that).

Patching Cargo.toml

You might need to patch Cargo.toml anyway if the version in debian is newer/older than the one specified. The buildprocess reads Cargo.toml so you need to down- or upgrade the version if it's not matching.

debian/rules

Change the entire file to this:

 #!/usr/bin/make -f

include /usr/share/dpkg/pkg-info.mk
include /usr/share/dpkg/architecture.mk
include /usr/share/dpkg/buildflags.mk
include /usr/share/rustc/architecture.mk
export CFLAGS CXXFLAGS CPPFLAGS LDFLAGS
export DEB_HOST_RUST_TYPE DEB_HOST_GNU_TYPE
export PATH := /usr/share/cargo/bin:$(PATH)
export CARGO=/usr/share/cargo/bin/cargo
export CARGO_HOME=$(CURDIR)/debian/cargo_home
export DEB_CARGO_CRATE=$(DEB_SOURCE)_$(DEB_VERSION_UPSTREAM)
export DEB_BUILD_MAINT_OPTIONS=hardening=+bindnow

%:
        dh $@ 

override_dh_auto_clean:
        dh_auto_clean
        rm -rf debian/cargo_registry


override_dh_auto_configure:
        $(CARGO) prepare-debian debian/cargo_registry --link-from-system
        rm -f Cargo.lock
        dh_auto_configure

lines 3 to 13 just set the relevant buildflags and tell dh to use the cargo wrapper script ( /usr/share/cargo/bin/cargo ). The sources (i.e. the packaged crates) get linked into the debian/cargo_registry directory. prepare-debian additionally takes care of telling cargo to use those crates and build offline. Cargo.lock needs to be removed before building because otherwise you'll get a checksum error.

Note: this is assuming that the buildsystem is automatically detected by dh. If that's not the case you'll need to specify it.

Building

If the source is prepared following above steps you should be able to build fully offline. In case you still spot a "Downloading crates" line in the buildlog check the source code if CARGO_HOME gets set at some point. This overrides the one we set so you'll need to patch that (and contact upstream about it, see here).

Notes

If you get stuck at some point ask on the #debian-rust IRC channel. Do not attempt update any standalone crate part of the gtk-rs stack because a) most likely, it won't work and b) it will break other programs/crates . Instead either wait until the new version lands in unstable or upgrade everything at once. The whole tree can be found here

GnomeRust_Packaging