Unable to use trybuild with macros that read files

[msrd0]

First of all, thanks for this amazing tool!

I'm trying to test a macro which reads files from the source directory of the crate. It reads the CARGO_MANIFEST_DIR environment variable (please let me know if there's a better way to do this) and resolves files relative to that directory. Unfortunately, with trybuild it points to $DIR/target/tests/<crate-name>, which doesn't contain the files I need.

Is it possible to have CARGO_MANIFEST_DIR point to the manifest that defines the test, or to the directory where the test file is located in?

[dtolnay]

You should use:

std::env::set_var(
    "CARGO_MANIFEST_DIR_OVERRIDE",
    std::env::var_os("CARGO_MANIFEST_DIR").unwrap(),
);

at the top of your #[test] that runs trybuild and then this in the macro:

let cargo_manifest_dir = std::env::var_os("CARGO_MANIFEST_DIR_OVERRIDE")
    .or(std::env::var_os("CARGO_MANIFEST_DIR"))
    .unwrap();

[msrd0]

This works, thanks. Just one problem that I noticed: My macro outputs "Help: Searching in directory $CARGO_MANIFEST_DIR" when the file it was looking for doesn't exist, which by its nature, will not always be the same path. However, trybuild for some reason doesn't replace that directory with $DIR but leaves the path untouched. Previously, it would output $DIR/target/tests/<crate-name> so maybe there's a problem where $DIR isn't used when there's no additional path segments behind it?

[msrd0]

I think the replacement isn't happening because of this: https://github.com/dtolnay/trybuild/blob/master/src/directory.rs#L18

Is there a particular reason why you only replace the source directory with trailing slashes?

[dtolnay]

Filed separately as #204.