r? @matklad

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r? @alexcrichton based on #4400

cc @behnam

Thanks for the PR! I do think though that cargo check --all-targets, for example, checks all benchmarks/tests/etc today. It still does with this patch, right?

I also think that we'd probably want to fix the behavior with cargo {bench,test} rather than tweak the defaults, as it's intended to "run all tests" and "run all benchmarks" I believe?

☔ The latest upstream changes (presumably #5152) made this pull request unmergeable. Please resolve the merge conflicts.

Yes, there is a test that cargo check --all-targets checks all lib/bin/example/test/bench targets.

After resolving conflicts and fixing a minor bug from #5152, I've additionally added a commit that makes cargo {bench,test} applies to all targets (and then the --all-targets flag is redundant), as requested.

The tests are failing but I'm pretty sure it's not a problem with my code. If you manually create the example from build::explicit_examples you can see that --all-targets is already a bit screwed even in older cargo releases:

$ cargo --version
cargo 0.24.0
$ cargo clean && cargo test >/dev/null 2>/dev/null; target/debug/examples/hello
Hello, World!
$ cargo clean && cargo test --all-targets >/dev/null 2>/dev/null; target/debug/examples/hello

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

I'll dig further, hints welcome.

It looks like cargo build --examples vs cargo test --examples will each respectively overwrite target/debug/examples/goodbye with the example binary vs a test binary that tests the example file.

Currently many of cargo's own tests implicitly depend on the fact that invocations like cargo test -v do not build the test-for-the-example but instead builds the example binary, for example build::explicit_examples. If my latest commit 1d31d9f is reverted/removed from this PR then the tests will start passing again.

Alternatively, it may be possible to switch cargo {bench,test} to "all-targets by default" without changing these other tests, by changing the target path of the test-for-the-example to be something other than target/debug/examples/goodbye. However this is also fairly invasive, was not the original intention of my PR, and I'd rather not get dragged into a rabbit hole being forced to fix existing deficiencies of cargo that are unrelated to the issue I was trying to fix. I could file an issue for this however.

TL;DR I'd suggest dropping 1d31d9f from this PR and abandoning the current suggestion to have cargo {bench,test} applied to all-targets by default, but file an issue about it detailing what the problem is and how to fix it (i.e. either rewrite several-dozen tests, or rewrite the target-paths for test binaries).

☔ The latest upstream changes (presumably #5176) made this pull request unmergeable. Please resolve the merge conflicts.

There was a simpler way of achieving what I wanted and I misunderstood how the existing code handles --all-targets. I'll open another more minimal PR.