Amend list of wired-in packages

[TeofilC]

Stack currently has special behaviour for a list of wired-in packages:

stack/src/Stack/Constants.hs

Lines 254 to 284 in 9375334

	wiredInPackages :: Set PackageName
	wiredInPackages = case mparsed of
	Just parsed -> Set.fromList parsed
	Nothing -> impureThrow WiredInPackagesNotParsedBug
	where
	mparsed = mapM parsePackageName
	[ "rts"
	-- Said to be not a \'real\' package
	, "ghc-prim"
	-- A magic package
	, "ghc-bignum"
	-- A magic package
	, "integer-gmp"
	-- No longer magic > 1.0.3.0 (GHC >= 9.0) and deprecated in favour of
	-- ghc-bignum. With GHC 9.8.4 at least, there seems to be no problem in
	-- using it.
	, "integer-simple"
	-- A magic package
	, "base"
	-- A magic package
	, "template-haskell"
	-- A magic package
	, "ghc"
	-- A magic package
	, "interactive"
	-- Type and class declarations at the GHCi command prompt are treated as
	-- if they were defined in modules all sharing a common package
	-- interactive. See 'Note [The interactive package]' at
	-- https://gitlab.haskell.org/ghc/ghc/-/blob/master/compiler/GHC/Runtime/Context.hs
	-- With GHC 9.8.4 at least, there seems to be no problem in using it.
	]

Many of these packages are no longer wired-in (and many never were). While ghc-internal is not on this list but it is a wired-in package.

We should re-examine this list and its uses. Ideally we would have as little special casing as possible.

See also a similar issue for Cabal: haskell/cabal#10087

See also this GHC MR to add the unit-id of ghc-internal to the output of ghc --info: https://gitlab.haskell.org/ghc/ghc/-/merge_requests/13297
and the cabal-install PR to make use of it: haskell/cabal#10982

[mpilgrem]

@TeofilC, thanks! I do look at that list from time to time (but infrequently: last time was April 2024). For consistency, I'll add ghc-internal (new to GHC 9.10).

As for its use by Stack, my understanding is reflected in the info box on GHC wired-in packages at: https://docs.haskellstack.org/en/stable/configure/yaml/project/#extra-deps (which I see is out of date).

I treat the list with some caution. It pre-dates my involvement with Stack and I've worried that fiddling with it might break something. So, on dropping items from the list, that happens slowly given that Stack still supports GHC 8.4.1 which ships with Cabal-2.2.0.0.

[TeofilC]

Thanks @mpilgrem . That is a very helpful link. I didn't realise the behaviour was documented (nice!).

So, on dropping items from the list, that happens slowly given that Stack still supports GHC 8.4.1 which ships with Cabal-2.2.0.0.

My plan on the cabal-install side is to make these things conditional on the version of GHC. Namely, GHC-9.14 will ship with a new field in the output of ghc --info and we will use that to determine whether we want the full list or just a reduced one.

I need to understand stack better but a similar strategy is probably the right thing to do here as well.

Then old versions won't break but new versions of GHC can benefit from the greater flexibility. And in particular will be able to benefit from reinstallable base and template-haskell