Relies on internals of Cargo and will break with existing / upcoming features

[epage]

executable_path assumes the location of the production binary based on the test binary

• This isn't the case when a user sets build.build-dir (added as of Cargo 1.91)
• This isn't the case if we approve the new build-dir layout (Re-organize build-dir by package + hash, rather than artifact type rust-lang/cargo#15010)
• This isn't the case if we change the build.build-dir default (Move build-dir out of the workspace to cargo-cache-home by default rust-lang/cargo#16147)

This problem was identified by the following crater run: rust-lang/rust#149852

Ways to resolve this

• Switch to getting the bin path from a macro that is run in the caller's code, e.g. see assert_cmd::cargo::cargo_bin!
• Add a fallback using the approved-but-not-stable runtime environment variable (feat(test): Make CARGO_BIN_EXE_ available at runtime  rust-lang/cargo#16421), e.g. assert_cmd::cargo::cargo_bin

[casey]

Thank's for opening this issue! What does "approved-but-not-stable" mean in practice?

[epage]

It depends on your level of risk tolerance. In this case, there is little risk. There are almost no other interpretations we can make for this env variable such that we would change the semantics in a way that breaks it. It already exists at compile time, so little reason to rename. The most likely scenario is we remove it but we're unlikely to find a reason to do so in the next 7 weeks.

[epage]

It depends on your level of risk tolerance. In this case, there is little risk. There are almost no other interpretations we can make for this env variable such that we would change the semantics in a way that breaks it. It already exists at compile time, so little reason to rename. The most likely scenario is we remove it but we're unlikely to find a reason to do so in the next 7 weeks.

[casey]

Gotcha, thank you!

I just merged #4, which prefers using $CARGO_BIN_EXE_{name} if it exists. Could you let me know if it looks reasonable? I tested it on nightly and it worked, and I also confirmed that it was using the environment variable.

[epage]

Looks good, thanks!

[casey]

Awesome, thank you!