`spago add-from-bower` command

[dariooddenino]

Right now adding a package to the set is a somewhat tedious manual process.

Getting inspiration from here: https://github.com/justinwoo/spacchetti/blob/master/scripts/from-bower.pl

It would be cool to be able to do spacchetti from-bower simple-json and having it appear as an addition in the packages.dhall file.

[f-f]

Maybe actually having the packages key in the spacchetti.dhall makes sense, as it would cover both this (by specifying a bower kind of dependency) and pulling in stuff from git (as detailed in #25, by specifying a git kind of dependency)

[f-f]

From the two issues linked above I got the impression that we should have some UX like:
spago package-set-add https://github.com/justinwoo/simple-json.git

This command would:

• fetch the repo (question: I guess in a temp folder? Because the verification might fail, so we don't want it in the .spago folder)
• check for the existence of a bower.json, read the dependencies, try to to find them into our local package-set. If we don't find a dependency, we find their repo address (question: how?) and repeat the process until we collect a list of packages we can add to the packages.dhall
• bonus point: we could check for a psc-package.json, crawl the package set it links to, and check if the versions of the dependencies match with our package set. If they don't match, we should output the list of not-matching deps. (question: should we anyways add this to the packages.dhall or should we fail?)

[LucianU]

Are the three features listed above still the desired ones?

Regarding point 3, what happens if we add the package but its dependencies don't match our package set? If the install will fail, I propose that we don't add the package.

[f-f]

@LucianU great questions. I think I now have a slightly different take on this:

• I changed my mind on the name of this command and I'm now again for the original suggestion, so you'd use it like spago add-from-bower spork.
  The reason is that right now 100% of the published packages have a bower.json that we can read. Even if in the future you might be able to publish packages without a bowerfile but only with a spago.dhall, in that case they'd already be in the package set.
  This also means that "point 3" from above is no longer valid.
• The way this should work is that:
  • We search for the package on the bower registry (eventually with the purescript- prefix if the user didn't specify it) with bower info some-package#some-version, to get their bower.json
  • from there we read the dependencies and try to to find them into our local package-set. If we don't find a dependency, we find their repo address (by searching again in the bower registry) and recur
  • This will give us a set of packages we can add to the packages.dhall