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Warn when installing with a non-default toolchain #16131

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ff31445
Set `RUSTUP_TOOLCHAIN_SOURCE` in rustup tests
smoelius Oct 17, 2025
4c7f9d0
Move `pkg` to testsuite/utils
smoelius Oct 17, 2025
9353e04
Implement test for 11036 cargo changes
smoelius Oct 19, 2025
c64e01a
Implement 11036 cargo changes
smoelius Oct 19, 2025
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11 changes: 11 additions & 0 deletions tests/testsuite/rustup.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,13 @@ fn real_rustc_wrapper(bin_dir: &Path, message: &str) -> PathBuf {
// The toolchain rustc needs to call the real rustc. In order to do that,
// it needs to restore or clear the RUSTUP environment variables so that
// if rustup is installed, it will call the correct rustc.
let rustup_toolchain_source_setup = match std::env::var_os("RUSTUP_TOOLCHAIN_SOURCE") {
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I don't think we should be doing anything based on the rustup we are running in

See also #16131 (comment)

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At the risk of sounding like an excuse, I was following the example of the code just below this:

cargo/tests/testsuite/rustup.rs

Lines 65 to 71 in ff31445

let rustup_toolchain_setup = match std::env::var_os("RUSTUP_TOOLCHAIN") {
Some(t) => format!(
".env(\"RUSTUP_TOOLCHAIN\", \"{}\")",
t.into_string().unwrap()
),
None => format!(".env_remove(\"RUSTUP_TOOLCHAIN\")"),
};

Should that following code be modified?

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This seems suspicious and I'd like to better understand why we do this

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Just FYI, I'm willing to make changes not directly related #11036.

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@smoelius smoelius Oct 22, 2025 •
edited
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How would you feel about rustc's path being determined in Cargo's build script rather than via environment variables in this function?

That is, I'm proposing that real_rustc_wrapper look something like this:

/// Creates an executable which prints a message and then runs the *real* rustc.
fn real_rustc_wrapper(bin_dir: &Path, message: &str) -> PathBuf {
    let real_rustc = PathBuf::from(env!("RUSTC"));
    let env = vec![("CARGO_RUSTUP_TEST_real_rustc", real_rustc)];
    make_exe(
        bin_dir,
        "rustc",
        &format!(
            r#"
                eprintln!("{message}");
                let r = std::process::Command::new(env!("CARGO_RUSTUP_TEST_real_rustc"))
                    .args(std::env::args_os().skip(1))
                    .status();
                std::process::exit(r.unwrap().code().unwrap_or(2));
            "#
        ),
        &env,
    )
}

EDIT: Also, please tell me whether you think a separate PR would be appropriate.

Some(t) => format!(
".env(\"RUSTUP_TOOLCHAIN_SOURCE\", \"{}\")",
t.into_string().unwrap()
),
None => format!(".env_remove(\"RUSTUP_TOOLCHAIN_SOURCE\")"),
};
let rustup_toolchain_setup = match std::env::var_os("RUSTUP_TOOLCHAIN") {
Some(t) => format!(
".env(\"RUSTUP_TOOLCHAIN\", \"{}\")",
Expand All @@ -78,6 +85,7 @@ fn real_rustc_wrapper(bin_dir: &Path, message: &str) -> PathBuf {
eprintln!("{message}");
let r = std::process::Command::new(env!("CARGO_RUSTUP_TEST_real_rustc"))
.args(std::env::args_os().skip(1))
{rustup_toolchain_source_setup}
{rustup_toolchain_setup}
{rustup_home_setup}
.status();
Expand Down Expand Up @@ -162,6 +170,7 @@ fn typical_rustup() {
// `~/.cargo/bin/rustc to use our custom rustup proxies.
let path = prepend_path(&cargo_bin);
p.cargo("check")
.env("RUSTUP_TOOLCHAIN_SOURCE", "default")
.env("RUSTUP_TOOLCHAIN", "test-toolchain")
.env("RUSTUP_HOME", &rustup_home)
.env("PATH", &path)
Expand All @@ -179,6 +188,7 @@ real rustc running
p.build_dir().rm_rf();

p.cargo("check")
.env("RUSTUP_TOOLCHAIN_SOURCE", "default")
.env("RUSTUP_TOOLCHAIN", "test-toolchain")
.env("RUSTUP_HOME", &rustup_home)
.env("PATH", &path)
Expand Down Expand Up @@ -249,6 +259,7 @@ fn custom_calls_other_cargo() {
// Set these to simulate what would happen when running under rustup.
// We want to make sure that cargo-custom does not try to use the
// rustup proxies.
.env("RUSTUP_TOOLCHAIN_SOURCE", "default")
.env("RUSTUP_TOOLCHAIN", "test-toolchain")
.env("RUSTUP_HOME", &rustup_home)
.with_stderr_data(str![[r#"
Expand Down