Custom flags for stack.yaml and stack command line tool

[mchaver]

I may be mistaken but it seems like this doesn't exist. Sometimes I make multiple stack.yaml files for differing package dependencies, different compilers, etc., but it involves a lot of repetition and shared similarities must be maintained. It would be better if I could make one stack.yaml file and have some set of flags for specific behavior depending on values I pass to stack at the command line.

A simple example is ghc vs ghcjs. Sometimes I want extra packages specifically for ghcjs so it would be nice if setup a single stack.yaml that says if I use a ghc flag it will compile the package with ghc and install one set of pacakges, if I use a flag for ghcjs, it will compile with ghcjs, a set of packages for both compilers and a set of packages for just ghcjs.

Another use case would be testing one package against different versions of a package.

[harendra-kumar]

#2559 may be the issue you are looking for.

[mgsloan]

Yes, this has been discussed quite a bit, but there is not yet a clear implementation path. Along with #2559, see also:

• Allow --pvp-bounds to use multiple snapshots #1568
• Method to combine multiple project stack.yaml files #732
• Feature request : multiple build configurations #392