Binaries aren't compiled and problem with `assert_cmd`

[cschwan]

Describe the bug Tarpaulin doesn't work together with [assert_cmd](), because tarpaulin doesn't build binaries (or deletes them). After working around the problem no line coverage is generated.

To Reproduce

cargo new mwe
cd mwe
echo 'assert_cmd = "2.0.2"' >> Cargo.toml
cat <<EOF >> src/main.rs

#[cfg(test)]
mod tests {
    use assert_cmd::Command;

    #[test]
    fn run_main() {
        Command::cargo_bin("mwe")
            .unwrap()
            .assert()
            .success();
    }
}
EOF
cargo build # needed to create the binary
cargo test # this works as expected
cargo tarpaulin --ignore-tests # this fails, see error below

The error:

Dec 17 16:30:02.461  INFO cargo_tarpaulin::config: Creating config
Dec 17 16:30:02.496  INFO cargo_tarpaulin: Running Tarpaulin
Dec 17 16:30:02.496  INFO cargo_tarpaulin: Building project
Dec 17 16:30:02.496  INFO cargo_tarpaulin::cargo: Cleaning project
   Compiling memchr v2.4.1
   Compiling libc v0.2.112
   Compiling either v1.6.1
   Compiling doc-comment v0.3.3
   Compiling predicates-core v1.0.2
   Compiling termtree v0.2.3
   Compiling lazy_static v1.4.0
   Compiling difflib v0.4.0
   Compiling regex-automata v0.1.10
   Compiling itertools v0.10.3
   Compiling predicates-tree v1.0.4
   Compiling bstr v0.2.17
   Compiling wait-timeout v0.2.0
   Compiling predicates v2.1.0
   Compiling assert_cmd v2.0.2
   Compiling mwe v0.1.0 (/tmp/mwe)
    Finished test [unoptimized + debuginfo] target(s) in 3.70s
Dec 17 16:30:06.277  INFO cargo_tarpaulin::process_handling::linux: Launching test
Dec 17 16:30:06.277  INFO cargo_tarpaulin::process_handling: running /tmp/mwe/target/debug/deps/mwe-517cb110a12ca1f1

running 1 test
test tests::run_main ... FAILED

failures:

---- tests::run_main stdout ----
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: CargoError { cause: Some(NotFoundError { path: "/tmp/mwe/target/debug/mwe" }) }', src/main.rs:12:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

failures:
    tests::run_main

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Error: "Test failed during run"

The problem is surely triggered because tarpaulin cleans the project. Using --skip-clean I can avoid this, but in that case I don't get line coverage. Is this expected? How do I get coverage for the main function?

[xd009642]

So to get coverage binaries actually have to be built with a specific set of linker flags. Also because -Clink-dead-code has frequently caused incremental compilation errors with rustc (and last I checked still does on certain platforms). Tarpaulin does clean by default. You also need --follow-exec to follow application spawns.

So what you want is probably something like cargo tarpaulin --run-types Bins Tests Lib --follow-exec. If that doesn't work maybe cargo tarpaulin --command Build --no-run && cargo tarpaulin --follow-exec --skip-clean

[cschwan]

@xd009642 thanks a lot! Your second options works for me. You can close this Issue as far as it concerns me.

[xd009642]

Cool, also I came across this in a discussion the other day and found just a simple cargo tarpaulin --follow-exec worked for a project using assert_cmd that I made. So may be worth trying that as well! (Link to discussion: https://github.com/xd009642/tarpaulin/discussions/908)

[cschwan]

@xd009642 Only adding --follow-exec didn't work in my case, although the binary was built (somewhere) ... but it works for me

[danieleades]

is this the same issue impacting cargo-msrv?

[cschwan]

As far as I can tell no, it seems that your test simply runs longer than the timeout that you specified (line 510), I'd simply increase it.