Relink-only seems to mess up dependency tracking

[edsko]

If we have a project with multiple libraries, with Y depending on X, if I make a change to X, and then call new-build in Y, it will not notice it needs to relink it with X. However, once I get in this situation, it seems something breaks and it will not notice it needs to recompile even when this involves more than relinking.

[dcoutts]

Need to know if this is still a problem, and if so specific instructions to reproduce.

[ezyang]

Related: https://ghc.haskell.org/trac/ghc/ticket/10161

[acarrico]

I've created a minimal test case for this annoying bug.

I don't think it is necessarily related to (https://ghc.haskell.org/trac/ghc/ticket/10161) since there is a new timestamp on the library. The executable is just stale. See the test case's readme, which shows the timestamps.

[acarrico]

BTW, I tested with this version:

[nix-shell:~/cabal-link-test]$ cabal --version
cabal-install version 2.0.0.1
compiled using version 2.0.1.0 of the Cabal library