Replace Boilerplate Monoid/Semigroup instances with generics

[hvr]

addresses #3169

[hvr]

@dcoutts @23Skidoo There's a few instances that we can't rewrite yet without more refactoring. Specifically those which have Bool flags without Data.Monoid.All or Data.Monoid.Any newtype-wrappers to guide the Monoid derivation.

[hvr]

Oh, and the Semigroup instances for TestSuite/Executable/Benchmark are partial via error!

instance Semigroup Executable where
  a <> b = Executable{
    exeName    = combine' exeName,
    modulePath = combine modulePath,
    buildInfo  = combine buildInfo
  }
    where combine field = field a `mappend` field b
          combine' field = case (field a, field b) of
                      ("","") -> ""
                      ("", x) -> x
                      (x, "") -> x
                      (x, y) -> error $ "Ambiguous values for executable field: '"
                                  ++ x ++ "' and '" ++ y ++ "'"

[hvr]

Interesting... the cabal-install changes seem to cause integration-test failures

[23Skidoo]

Nice! Boolean flags should use Any, I think.

[hvr]

Nice! Boolean flags should use Any, I think.

there are a few cases which have it inverted:

instance Semigroup Library where
 -- ...
       libExposed     = libExposed a && libExposed b, -- so False propagates

instance Semigroup BuildInfo where
  a <> b = BuildInfo {
    buildable           = buildable a && buildable b,
   -- ...
 }

[23Skidoo]

Merged, thanks!

[hvr]

@23Skidoo what are your plans re 1.24 branch? I mostly want to know to decide what to do about the nix-local branch

[23Skidoo]

@hvr Well, I didn't want to backport this into 1.24 initially, but it's probably not a very big deal after all. And merges will be easier. I just need to find a way to download all custom setup scripts from Hackage to check that #3195 didn't break anything.

[hvr]

That shouldn't be too hard:

cabal list --simple | awk '{ print $1 }' | uniq

gives you a list of all package names,

and

curl -s --fail http://hackage.haskell.org/package/$PKGNAME/src/Setup.lhs || curl -s --fail http://hackage.haskell.org/package/$PKGNAME/src/Setup.hs

tries to retrieve you the latest version of $PKGNAME's Setup.lhs or Setup.hs

you could also try to be more clever and look at the .cabal files first (e.g. from your 00-index.tar ball) and check for the build-type before downloading the Setup.(l)hs files...

[23Skidoo]

you could also try to be more clever and look at the .cabal files first (e.g. from your 00-index.tar ball) and check for the build-type before downloading the Setup.(l)hs files...

Yep, that's what I want to do.

[hvr]

In that case:

cd $TMP
tar xf ~/.cabal/packages/hackage.haskell.org/00-index.tar.gz 
find -name '*.cabal' | xargs grep -li '^build-type:.*custom' | cut -f2 -d/ | uniq

[23Skidoo]

@hvr Thanks! That was easier than I expected. Uploaded the results to https://github.com/23Skidoo/all-custom-setups. And it turns out llvm-general actually uses configPrograms in its setup script.

[hvr]

@23Skidoo I think that specific case in llvm-general can be made more compatible by providing a function configPrograms with the old type-sig (as it's only used as a function, rather than a field-record-label). and name the actual field differently, e.g. configPrograms_

PS: c.f.

cabal/Cabal/Distribution/Simple/Configure.hs

Lines 690 to 693 in 5a77348

	-- | More convenient version of 'configPrograms'. Results in an
	-- 'error' if internal invariant is violated.
	configPrograms' :: ConfigFlags -> ProgramConfiguration
	configPrograms' = maybe (error "FIXME: remove configPrograms") id . getLast' . configPrograms

[23Skidoo]

Yes, it should work given that the script doesn't use explicit import lists.

[hvr]

@23Skidoo btw, @dcoutts tells me he "used to have a script to try compiling all custom Setup.hs scripts with old and new Cabal lib version to look for breakages"

did you try to compile those Setup.hs files or did you just grep for configPrograms?

[23Skidoo]

@hvr Just grepped.

[hvr]

@23Skidoo fwiw, if you're still worried about merging to 1.24, you could try merging only the cabal-install parts, or we could simply back out the ConfigFlags instance from the part merged to 1.24 (I'll happily prepare a PR if you want the latter variant)

[23Skidoo]

@hvr Cherry-picked all your patches into 1.24.