Help text wrongly states that the default --builddir is dist

[andreasabel]

Help text for cabal install still claims that the default --builddir is dist (rather than dist-newstyle).

$ cabal install --help | grep -B1 dist
 --builddir=DIR                 The directory where Cabal puts generated build
                                files (default dist)

[phadej]

This is indeed embarrassing. If you grep the code, you will notice that the help message comes from Cabal, not cabal-install:

cabal/Cabal/src/Distribution/Simple/Setup.hs

Lines 2159 to 2171 in b6d0516

	optionDistPref :: (flags -> Flag FilePath)
	-> (Flag FilePath -> flags -> flags)
	-> ShowOrParseArgs
	-> OptionField flags
	optionDistPref get set = \showOrParseArgs ->
	option "" (distPrefFlagName showOrParseArgs)
	( "The directory where Cabal puts generated build files "
	++ "(default " ++ defaultDistPref ++ ")")
	get set
	(reqArgFlag "DIR")
	where
	distPrefFlagName ShowArgs = ["builddir"]
	distPrefFlagName ParseArgs = ["builddir", "distdir", "distpref"]

(defaultDistPref is defined in the same file).

I think that the underlying reason is the same as why there is

% cabal build --help|grep libdir 
 --libdir=DIR                   installation directory for libraries
 --libsubdir=DIR                subdirectory of libdir in which libs are
 --dynlibdir=DIR                installation directory for dynamic libraries

etc parameters in cabal v2-build which shouldn't be there, as they don't have any effect. However Cabal's builddir is repurposed to do reasonable thing for cabal-install. It's somewhat hard to trace where from exactly builddir configuration param is

TL;DR, this is IMO a symptom of v2 commands not having sane, independent cli-argument implementation. There are plenty of such small annoyances. I guess the symptoms could be fixed one-by-one: in this case parameterize optionDistPref by default location and use dist-newstyle in cabal-install); however fixing the underlying cause needs a very determined person.

[phadej]

This is not oneline change, multiple files, in separate packages have to be changed. (This shouldn't be that hard, but that is a consequence of a hard underlying problem I mention: there is a sizable technical debt).

[mpickering]

@phadej is correct about how to fix this issue, the change in #8833 seems the wrong way to go.