"Could not execute process (never executed)" with [lib] harness = false

[SimonSapin]

http://doc.crates.io/manifest.html#configuring-a-target suggests that harness = false can be used in the [lib] section of Cargo.toml. Let’s try it:

/tmp% cargo new foo
/tmp% cd foo 
/tmp/foo% echo -e '[lib]\nharness=false' >> Cargo.toml
/tmp/foo% cargo test -v
   Compiling foo v0.1.0 (file:///tmp/foo)
     Running `rustc src/lib.rs --crate-name foo --crate-type lib -g -C metadata=9476bb3dbe366490 -C extra-filename=-9476bb3dbe366490 --out-dir /tmp/foo/target/debug --emit=dep-info,link -L dependency=/tmp/foo/target/debug -L dependency=/tmp/foo/target/debug/deps`
     Running `rustc src/lib.rs --crate-name foo --crate-type lib -g --out-dir /tmp/foo/target/debug --emit=dep-info,link -L dependency=/tmp/foo/target/debug -L dependency=/tmp/foo/target/debug/deps`
     Running `/tmp/foo/target/debug/foo-9476bb3dbe366490`
Could not execute process `/tmp/foo/target/debug/foo-9476bb3dbe366490` (never executed)

Caused by:
  Could not execute process `/tmp/foo/target/debug/foo-9476bb3dbe366490` (never executed)

Caused by:
  No such file or directory (os error 2)

--test is indeed not passed, but --crate-type lib still is so no executable is created.

Grepping Cargo’s source shows an example in tests/test_cargo_test.rs where harness = false is used in [[test]], which makes more sense.

So:

• The docs should show harness = false in a [[test]] section, not [lib].
• harness = false in [lib] should probably emit a warning and be otherwise ignored, since it doesn’t work. Or make Cargo emit in error and abort.
• With harness = false in [[bin]], there is no way that I can find to tell whether an executable is being built for testing or not. Maybe pass --cfg test?

[alexcrichton]

Hm yeah I think harness = false in a library should be ignored unless Cargo passes --cfg test which I actually wanted to do in the past.

Continuing to pass --crate-type lib is indeed a bug, however, in any case.

[alexcrichton]

I'm gonna tag this as E-easy as this is likely a pretty easy-to-approach project for anyone looking to dive into Cargo!

[SimonSapin]

Also worth documenting, as I don’t see it http://doc.crates.io/manifest.html and found out the hard way (ok, it was easily fixed and not that dramatic): when Cargo.toml doesn’t contain any [[test]] section, cargo test will enumerate tests/*.rs files and build/run an integration test crate for each of them. But as soon as you add one [[test]] section (say, to add harness = false to it), Cargo stops doing that enumeration and ignores the rest of the files. One has to list an explicit [[test]] section for each of them, even if with just a name.

[TheNeikos]

Going to try and tackle this

[TheNeikos]

@alexcrichton Regarding your comment about passing --cfg test if harness is set to false.

If I understood it correctly the behaviour should be:

• harness = true Default, nothing changes here
• harness = false Ignore it, but still pass --cfg test

Is that correct?

[alexcrichton]

Sounds good to me!

[TheNeikos]

@alexcrichton Thanks

[alexcrichton]

Unfortunately this is blocked on rust-lang/rust#33670

[sanxiyn]

This is unblocked.

[MightyPork]

I just got the same puzzling error in intellij-rust, and I think it may be related to shutting down an ongoing build. Running cargo run manually works, but CLion is unable to run it after a build finishes.

In fixed it by deleting target/ and rebuilding from scratch