Cabal build-tool-depends doesn't work

[domenkozar]

See the following diff: https://github.com/sol/markdown-unlit/pull/13/files

Which results into:

$ cd example && cabal install --only-dependencies --enable-tests && cabal configure --enable-tests && cabal build && cabal test
Resolving dependencies...
All the requested packages are already installed:
Use --reinstall if you want to reinstall anyway.
Resolving dependencies...
Configuring nifty-library-0.0.0...
Preprocessing test suite 'readme' for nifty-library-0.0.0..
Building test suite 'readme' for nifty-library-0.0.0..
ghc: could not execute: markdown-unlit

I thought maybe there was a bug in Cabal 2.0, but it also fails with 2.2: https://travis-ci.org/nikita-volkov/hasql/jobs/423628586

[hvr]

Due to technical limitations of old-build, build-tool-depends only fully works w/ the nix-style new-* commands; see also documentation (https://cabal.readthedocs.io/en/latest/developing-packages.html#pkg-field-build-tool-depends) which points out this gotcha:

Cabal can make sure that specified programs are built and on the PATH before building the component in question. It will always do so for internal dependencies, and also do so for external dependencies when using Nix-style local builds.

Do we need to make the documentation clearer?

[domenkozar]

Thanks @hvr :)

It is fine for the package to be the current one, in which case this is termed an internal, rather than external executable dependency.

I don't understand this sentence, what does it mean to be "current one"?

[domenkozar]

Ah, does it mean any target defined in current cabal file?

[domenkozar]

#5561