[Pkg-rust-maintainers] [Debian Wiki] Update of "Teams/RustPackaging/Policy" by Infinity0

Tue Feb 6 20:57:11 UTC 2018

On Tue, Feb 06, 2018 at 08:12:00PM +0000, Ximin Luo wrote:
> Right, it does not do that currently. For git2 we have:
> 
> [features]
> curl = ["libgit2-sys/curl"]
> 
> which cargo treats as "git2-with-feature-curl must depend on libgit2-sys-with-feature-curl"

AFAIK, debcargo should handle that correctly, by making
librust-git2-version+curl-dev depend on
librust-git2-sys-version+curl-dev. Does it not?

> For num-bigint we have
> 
> [dependencies.rand]
> optional = true
> 
> which cargo treats as "num-bigint-with-feature-rand must depend on the rand crate".
> 
> and something similar for serde.

Does debcargo not handle that correctly already? It should.

> OTOH, we also have various crates that have dependencies with "{ default-features = false }", e.g. chrono-0.4 on num-0.1-with-default-features-false.
> 
> So for all of these reasons I think it would be cleaner in the end not to special-case the "default" feature by combining it with the bare crate (as debcargo currently seems to be doing). Rather, we should:
> 
> 1. have the bare crate Provides: the X feature, only if all deps of X are satisfied by it (for any X, including X = "default"). From the output of the winapi-0.3 crate, it seems we're already doing this. if not, then X needs to go in a real separate Package stanza.

Debatable. We could perhaps have an option in debcargo (perhaps via the
config file) to split out +default-dev into a separate package. But
given that all library crate packages just consist of source code, why
does it matter? I'd rather intentionally bundled +default-dev into -dev
for developer convenience; we don't need *maximum* feature granularity.

> 2. translate crate-dependencies to +default debian dependencies, unless it is annotated with default-features = false in which case we translate it to the bare debian package.

debcargo already does (2) exactly like that; it uses +default-dev if
default-features, or -dev if default-features=false.

> This seems acceptable with current policy. For context, in practise this affects about 4 crates out of the 135 that I've tried so far.
> 
> X
> 
> Josh Triplett:
> > debcargo is supposed to add all the corresponding Depends for the
> > "default" feature to the base crate, to go along with that Provides. If
> > it doesn't, that seems like a bug.
> > 
> > On Tue, Feb 06, 2018 at 05:38:00PM +0000, Ximin Luo wrote:
> >> Hey Josh,
> >>
> >> All versions of debcargo [1] have generated a Provides: +default for all library crates. This breaks for packages where the default feature pulls in extra dependencies on top of the bare create - examples are git2, num-bigint, semver.
> >>
> >> I had thought the packaging policy needs updating but it is actually fine, so I've just tweaked the wording to be a bit clearer about it. It is debcargo itself that needs to generate explicit Package: stanzas for +default when they pull in more dependencies than the bare crate does, e.g. [2]. Vasudev says he's currently working on a fix.
> >>
> >> This was detected by running `cargo build` as part of dh_auto_test, so I think it is good to continue doing this for all crates in the future.
> >>
> >> X
> >>
> >> [1] I checked as far back as 1.3.0 + 3 commits (b5b880b), before that it requires older openssl which I didn't bother installing.
> >> [2] https://anonscm.debian.org/git/pkg-rust/debcargo.git/tree/tests/sh/configs/git2-0.6/debian/control?id=pu/cargo-build-everything
> >>
> >> Josh Triplett:
> >>> Can you elaborate a bit on the goal here?
> >>>
> >>> On Tue, Feb 06, 2018 at 12:42:09PM -0000, Debian Wiki wrote:
> >>>> Dear Wiki user,
> >>>>
> >>>> You have subscribed to a wiki page or wiki category on "Debian Wiki" for change notification.
> >>>>
> >>>> The "Teams/RustPackaging/Policy" page has been changed by Infinity0:
> >>>> https://wiki.debian.org/Teams/RustPackaging/Policy?action=diff&rev1=20&rev2=21
> >>>>
> >>>> Comment:
> >>>> make it clear that it is not always appropriate to Provides: the `default` feature
> >>>>
> >>>>   
> >>>>   A library crate must also generate binary packages for every Cargo "feature" it declares, named `librust-cratename-version+featurename-dev`.  Cargo crate names do not allow a plus sign (`+`) in them, so this package name will not conflict with the package name for any other Rust library crate or feature package.  If the feature name contains underscores (`_`), the corresponding binary package name must replace them with dashes (`-`).
> >>>>   
> >>>> - Each feature package must pull in all the dependencies needed to build a package that depends on that feature of the crate, including any dependencies on other features of the same crate.  If a feature package pulls in no additional dependencies, the main `librust-cratename-version-dev` package can use a versioned Provides to supply that feature package.  The `librust-cratename-version-dev` should normally incorporate any dependencies required to build the `default` feature of the crate, and use a versioned Provides to supply the `librust-cratename-version+default-dev` package as well as any feature packages for features that require no additional dependencies beyond `default`.
> >>>> + Each feature package must pull in all the dependencies needed to build a package that depends on that feature of the crate, including any dependencies on other features of the same crate.  If a feature package pulls in no additional dependencies, the main `librust-cratename-version-dev` package can use a versioned Provides to supply that feature package.  (For example, the `librust-cratename-version-dev` would normally incorporate any dependencies required to build the `default` feature of the crate, and use a versioned Provides to supply the `librust-cratename-version+default-dev` package as well as any feature packages for features that require no additional dependencies beyond `default`.)
> >>>>   
> >>>>   Each feature package must have a versioned dependency on the same version of the main `librust-cratename-version-dev` package.  If a feature of the crate depends on another feature of the same crate, the corresponding feature package for the first feature must have a dependency on the same version of the feature package for the second feature.
> >>>>   
> >>
> >>
> >> -- 
> >> GPG: ed25519/56034877E1F87C35
> >> GPG: rsa4096/1318EFAC5FBBDBCE
> >> https://github.com/infinity0/pubkeys.git
> > 
> > _______________________________________________
> > Pkg-rust-maintainers mailing list
> > Pkg-rust-maintainers at lists.alioth.debian.org
> > https://lists.alioth.debian.org/mailman/listinfo/pkg-rust-maintainers
> > 
> 
> 
> -- 
> GPG: ed25519/56034877E1F87C35
> GPG: rsa4096/1318EFAC5FBBDBCE
> https://github.com/infinity0/pubkeys.git