Re: [PATCH 1/7] build-system: Add cargo build system.

[David Craven]

> Is this correct?  What happens when test-target is not specified?  I see
> below that the target is hard-coded to “test”.  Maybe set it to “test”
> here and use it on the build side?

> Shouldn’t this respect “test-target”?

There is no other build target than test. Functions that are tests
have an attribute #[cfg(test)] above them. Running cargo test tells
cargo to run all functions that are annotated like that.

> I’m not familiar with Rust so I don’t know what crates are.  Are they
> actually source files?  Are they archives?

A crate is a tar.gz file which contains the source.

> You write that we are replacing references in Cargo.toml with store
> paths but I see no evidence of this.  Could you please clarify?

These patches only build packages without dependencies. I have
packages importing/building with a simple dependency structure.

I'm refactoring the importer to allow recursive imports, and then I'll
try to package cargo with it.

> Why only use “cargo install” in case there are executables?  Can we
> detect this by looking at some description file of the package?  It
> doesn’t seem right to unconditionally end on #t.

So we installed the source. At this point the build system can use it. The
only time we install binaries is when the crate contains an executable or
a script. In those cases `cargo install` should work. If there isn't an
executable we don't care if it fails.

> I don’t understand this.  Does this mean that currently dependencies are
> always bundled?

No. This is to prevent cargo from fetching the missing dependencies from
crates.io and to use our crates. Rust/LLVM performs aggressive optimization,
executables include all their rust symbols. You can write a C
compatible library,
but most crates are meant for Rust development. They have their own binary
format called *.rlib that is like an *.a file. The main focus for now
is building
cargo. The situation should improve, but this is how other distros are packaging
crates currently.