Add a --no-examples switch to cargo test

[faulesocke]

cargo test has an --examples switch which checks "that all examples compile". However, this seems to be the default when running cargo test, which makes the switch effectively a no-op.

But sometimes when I do refactoring, I first wan't to check whether all library tests run and then I want to fix the examples. Therefore, having a --no-examples switch would be really helpful.

[joshtriplett]

This seems reasonable. If you'd be interested in writing a PR, we'd likely accept it.

[ehuss]

--examples is not a no-op. It tests only examples, nothing else.

One approach to skip examples is to do cargo test --lib which will just do unit tests.

Starting in Rust 1.27 (beta), you can also do unit tests and integration tests (without examples) with cargo test --tests --lib.

[joshtriplett]

@ehuss Thanks for the clarification! In that case, perhaps what we need here is just an added sentence in the documentation, pointing people to the relevant options.

[ehuss]

@joshtriplett I've been thinking for a while now about writing more detailed documentation about the default target and profile selection, and how target options like --tests work. I'm not sure how extensive it would be, or where it would live. I'd be reluctant to put it in --help since most commands already have a long stream of unorganized paragraphs. I was thinking maybe a new chapter in the Cargo Book. But if it is buried away somewhere where nobody will see it, it might not be useful. I haven't gotten very far in organizing my thoughts, though. I was thinking about hitting up the cargo team and/or docs team to see what people thought, but I haven't gotten around to it.

[faulesocke]

@ehuss Thank you very much! Shall I leave the issue open for tracking possible documentation changes or shall I close it?