External subcommands are already able to inherit the jobserver from
env since #10511. However, users reported that they've expected
`cargo run` to behave the same as external subcommands.
A popular example "cargo-xtask" pattern is used as scripting to run
arbitrary tasks. Users may want to invoke `cargo run` from Make and
expect some parallelism. This PR provides such an ability to the
general `target.<...>.runner`, which affects `cargo test`,
`cargo bench`, and `cargo run`.
Note that this PR doesn't create any jobserver client if there is no
existing jobserver from the environment. Nor `-j`/`--jobs` would create
a new client. Reasons for this decision:
* There might be crates don't want the jobserver to pollute their
file descriptors, although they might be rare
* Creating a jobsever driver with the new FIFO named pipe style is not
yet supported as of `jobserver@0.1.26`. Once we can create a named
pipe-based jobserver, it will be less risky and inheritance by
default can be implemented.
* Collapse the nested cargotest::support module into the cargotest
module (merge the mod.rs's)
* Rename the cargotest module to support
* Nest the top-level hamcrest module into support
By rewriting the tests, with rerast (https://github.com/google/rerast),
to use the newly introduced "at" method.
First I added the following temporary function to cargotest::support:
pub fn project_foo() -> ProjectBuilder {
project("foo")
}
Then I defined the following rewrite.rs:
use cargotest::support::{ project, project_foo };
fn rule1(a: &'static str) {
replace!(project("foo") => project_foo());
replace!(project(a) => project_foo().at(a));
}
Then I ran rerast:
cargo +nightly rerast --rules_file=rewrite.rs --force --targets tests --file tests/testsuite/main.rs
Finally I searched and replaced the references to project_foo with
argument-less project (a little awkardly on macOS with a git clean).
find tests -type f -exec sed -i -e 's/project_foo/project/g' {} +
git clean -d tests
