Add a way to make builds with one job deterministic #5009
Description
Currently cargo build -j 1 builds crates, that can be built in parallel, in random order:
This is very painful when trying write a cargotest for a complex situation involving multiple crates:
#[cargo_test]
fn deterministic_builds() {
let p = project()
.file(
"a/Cargo.toml",
r#"
[package]
name = "a"
version = "0.0.1"
authors = []
"#,
)
.file(
"a/src/lib.rs",
r#"
pub fn a() {}
"#,
)
.file(
"b/Cargo.toml",
r#"
[package]
name = "b"
version = "0.0.1"
authors = []
"#,
)
.file(
"b/src/lib.rs",
r#"
pub fn b() {}
"#,
)
.file(
"c/Cargo.toml",
r#"
[package]
name = "c"
version = "0.0.1"
authors = []
"#,
)
.file(
"c/src/lib.rs",
r#"
pub fn c() {}
"#,
)
.file(
"d/Cargo.toml",
r#"
[package]
name = "d"
version = "0.0.1"
authors = []
"#,
)
.file(
"d/src/lib.rs",
r#"
pub fn d() {}
"#,
)
.file(
"Cargo.toml",
r#"
[package]
name = "foo"
version = "0.0.1"
authors = []
[dependencies]
a = { path = "a" }
b = { path = "b" }
c = { path = "c" }
d = { path = "d" }
"#,
)
.file(
"src/lib.rs",
r#"
extern crate a;
extern crate b;
extern crate c;
extern crate d;
pub use a::a;
pub use b::b;
pub use c::c;
pub use d::d;
"#,
)
.build();
p.cargo("build")
.arg("--verbose")
.arg("-j")
.arg("1")
.with_stderr(
"\
[COMPILING] a v0.0.1 ([CWD]/a)
[RUNNING] `rustc --crate-name a [..]
[COMPILING] b v0.0.1 ([CWD]/b)
[RUNNING] `rustc --crate-name b [..]
[COMPILING] c v0.0.1 ([CWD]/c)
[RUNNING] `rustc --crate-name c [..]
[COMPILING] d v0.0.1 ([CWD]/d)
[RUNNING] `rustc --crate-name d [..]
[COMPILING] foo v0.0.1 ([CWD])
[RUNNING] `rustc --crate-name foo [..]
[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
",
)
.run();
}(this test will pass, 1 every 24 times!).
Maybe... we should even make -j 1 being deterministic be the default... Issues about this have been filled in the past #2607 .