De-duplicating buildInplaceUnpackedPackage and buildAndInstallUnpackedPackage

[alt-romes]

It seems that there are a lot of things in common between buildInplaceUnpackedPackage and buildAndInstallUnpackedPackage, however, there is also a lot of duplication between the two.

In my opinion, it would be better to factor the common bits (not changing any behaviour... best effort) and have a single function for both (similar) use cases. The subtle bugs due to the duplication and not doing things uniformly for the two situations seems much worse than possibly incurring a regression in the behaviour change, especially going forward.

[andreabedini]

Yes, absolutely, but let's make sure we factor out common functionality (as you say) rather than jumble them toghether. I see many cases where "different things" are forced through a same code path leaving up with a bunch of case-splitting at the bottom. I.e.

f :: A -> IO ()
f = ... (a lot of duplication)

g :: B -> IO ()
g = ... (a lot of duplication)

ends up being "simplified" as

fg :: Either A B -> IO ()
fg ab = do
  ...
  case ab of
   A -> ...
   B -> ...
  ...
  case ab of
   A -> ...
   B -> ...
  ...

rather than e.g.

f :: A -> IO ()
f = do
  common1
  specific
  common2
  specific

g :: B -> IO ()
g = do
  common1
  specific
  common2
  specific

I am sure this is what you have in mind. I just needed to get this out of my chest 😂