cross-compilation doctests warning should not be behind verbose flag

[timfish]

^{Main tracking issue: #7040}

Problem

I just spent a lot longer than I'm willing to admit trying to work out why my doctests were not running. After working out I'd done everything correctly I finally tried --verbose and found the warning about cross-compilation not being supported.

cargo test completes successfully and I've not even known that the doctests have been skipped for months! Why is this warning hidden behind the verbose flag?

Steps

Create a src file with failing doc tests:
lib.rs

/// ```
/// panic("something')
/// ```
pub fn my_function() { }

Ensure you're building for another target. For me, this was on an M1 mac with the following .cargo/config to make this a cross platform build:

[build]
target = "x86_64-apple-darwin"

Run cargo test --doc

Results in no output after the build output.

Version

cargo 1.69.0

[weihanglo]

It was an intentional choice in #10132. Warning for every doctest target may be noisy. Could be improved by warning just once in normal mode if there is a cross-compile doctest, hinting people to use --verbose to see the full list of skipped doctest targets.

Relevant code is here:

cargo/src/cargo/ops/cargo_test.rs

Lines 190 to 205 in 0e93732

	CompileKind::Target(target) => {
	if target.short_name() != compilation.host {
	// Skip doctests, -Zdoctest-xcompile not enabled.
	config.shell().verbose(|shell| {
	shell.note(format!(
	"skipping doctests for {} ({}), \
	cross-compilation doctests are not yet supported\n\
	See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#doctest-xcompile \
	for more information.",
	unit.pkg,
	unit.target.description_named()
	))
	})?;
	continue;
	}
	}

[weihanglo]

Just a friendly reminder. It would be great for collaboration if people always strive to provide reproducible steps and version information for their issues. That may increase the chance for anyone wanting to fix gets started sooner.

[timfish]

provide reproducible steps and version information for their issues

Apologies. Just added these.

[weihanglo]

Labeled as P-low Priority: Low as we are considering to stabilize -Zdoctest-xcompile, so this warning may be unnecessary. There is no ETA though.

[1garo]

Would be okay if I work on this one? @weihanglo

[1garo]

I'm just having trouble building, I been having the message below in some crates:

error[E0658]: use of unstable library feature 'once_cell'

Any ideia?

[Rustin170506]

Try to use the latest stable version or nightly version rustc.