#925: More flexible constraints, specified via local preferences file
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Reporter: snoyberg | Owner:
Type: enhancement | Status: new
Priority: normal | Milestone: cabal-install-0.14
Component: cabal-install tool | Version: 1.10.2.0
Severity: normal | Keywords:
Difficulty: unknown | Ghcversion:
Platform: |
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Changes (by kosmikus):
* type: defect => enhancement
* milestone: => cabal-install-0.14
Comment:
I've changed your bug into an enhancement request. What you're describing
is intended behaviour. A constraint passed on the command line acts the
same as a constraint put in the build-depends of a package, i.e., it not
only restricts the range of versions, but also causes the package to
actually be installed.
The closest to what you want that currently exists is --preference, and it
should actually be sufficient in most cases. A --preference constraint
does not prevent excluded versions from selected at all, but it will first
try all preferred versions.
I appreciate the attempt you make with cabal-nirvana, but I don't like
that it works by actually changing the downloaded files. Cabal already
supports a global preferences file that's downloaded from Hackage. It
should probably support local files with preferences, too. That would be
relatively easy to change.
So there are two possible enhancements in this issue:
* introduce a way to easily specify a large number of local
preferences,
* next to constraints introduced by --preference and --constraint
The mail
http://www.mail-archive.com/haskell-cafe@haskell.org/msg96962.html
as well as the surrounding thread are also somewhat related.
--
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/925#comment:2>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects
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