cabal-install rebooted?

[Bardur Arantsson]

Hi all,

So, I was feeling a bit frustrated about the complexity of the Cabal
sandbox code, and when I get frustrated I start deleting things...

Just for funzies I tried deleting all the obvious non-sandbox code
in cabal-install, and here's the result:


https://github.com/BardurArantsson/cabal/commit/27aa116cc0ab3c824bd80c175ecbe51955dd9271

As you can see it means the removal of 218 lines, but most importantly
IMO it drastically simplifies the code in some places, notably
loadConfigOrSandboxConfig (funnily enough) becomes trivial and
classifyPackageEnvironment disappears (conincidence? I think not.). I'm
sure there are quite a few other things that could also be removed. I've
left a few notes sprinkled in the code marked by XXX.

Obviously, this isn't mergeable as-is[1] and I mostly did it for a lark,
but what do you guys think? Is this something that could/should be
pursued further? I seem to recall hearing some rumblings that some
people really wanted cabal-install to be sandbox-only. I think this
little Proof of Concept shows that it would be beneficial at least from
a code complexity/maintenance perspective.

(I certainly know that I've been getting really frustrated trying to
implement #2810 because the code is incredibly *gnarly* because it has
to account for a lot of combinations of things, and this might be a good
way to try to reverse the tide of option-itis.)

Regards,

/b

[1] For one thing, there's need to be some sort of deprecation period of
non-sandbox mode at the very least. :)