[Hackage] #198: outline for revamp of "cabal install" and upgrade behavior

[Hackage]

#198: outline for revamp of "cabal install" and upgrade behavior
---------------------------------+------------------------------------------
  Reporter:  guest               |        Owner:         
      Type:  defect              |       Status:  new    
  Priority:  normal              |    Milestone:         
 Component:  cabal-install tool  |      Version:  1.2.3.0
  Severity:  normal              |   Resolution:         
  Keywords:                      |   Difficulty:  normal 
Ghcversion:  6.8.2               |     Platform:  Linux  
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Changes (by ijones):

  * summary:  cabal install foo should upgrade foo if there's a newer
              version => outline for revamp of "cabal
              install" and upgrade behavior

Old description:

> As in #168
>
> if I have foo-1.0 installed, and foo-2.0 is available, "cabal install
> foo" should upgrade foo to version 2.0
>
>  1. If the user specifies a package without a version, and a newer
> version is available on Hackage, that newer version should be installed.
>  2. If the system is installing dependencies on "foo", if the dependency
> can be satisfied locally, do not install the "hackage" version, even if
> it's newer.
>  1. If a user specifies a specific version
>    1. if that version is available locally, use that
>  1. if a user specifies a version range
>    1. if that version can be satisfied locally, but not from hackage, use
> the local version
>    1. if a newer version on Hackage satisfies the dependency too, install
> that.

New description:

 I'm consolidating #168 and #197 here.

 = Use cases =
  * "cabal install world --deep" (upgrades all packages, whether required
 or not)
    * do we delete obsolete packages too?
  * "cabal install world" (upgrades only "interesting" packages and any
 required upgrades)
  * "cabal install foo" (upgrades foo and any required upgrades from foo)
  * "cabal install foo --deep" (upgrades foo and all its dependencies
 whether required or not)

 = Definitions =
  * '''Interesting packages''' are packages that a user specifically
 requests, rather than a package that's installed because of a dependency.
  * '''Obsolete packages''' are packages which were installed as a
 dependency on an interesting package, but are no longer depended on by any
 interesting package.
  * '''required upgrades''' - if the new version of foo requires a new
 version of Bar, then we are required to upgrade bar.

 = behavior of "install foo" =

 if I have foo-1.0 installed, and foo-2.0 is available, "cabal install foo"
 should upgrade foo to version 2.0

  1. If the user specifies a package without a version, and a newer version
 is available on Hackage, that newer version should be installed.
  2. If the system is installing dependencies on "foo", if the dependency
 can be satisfied locally, do not install the "hackage" version, even if
 it's newer.
  1. If a user specifies a specific version
    1. if that version is available locally, use that
  1. if a user specifies a version range
    1. if that version can be satisfied locally, but not from hackage, use
 the local version
    1. if a newer version on Hackage satisfies the dependency too, install
 that.

 = background from duncan re gentoo =
 I'm glad this is in, I just want to think about the user interface for a
 moment; for these variations on installing/upgrading stuff, what mix of
 top level commands or modifying flags they should use.

 So at the moment the behaviour is:

 {{{
 cabal install foo
 }}}

 means install the package foo only if it is not already installed. If a
 newer version is available it is ignored. Though if someone specifies
 cabal install foo-1.1 then that really will be installed, even if foo-1.0
 is installed already. This is probably not what most people want (see #168
 & #198).

 {{{
 cabal upgrade
 }}}

 means upgrade all upgradable packages. Presumably we upgrade them in
 dependency order.

 There are more variations that people would probably like so the question
 is, what variations, and how should the user interface allow those things
 to be expressed.

 One data point that I am familiar with is gentoo's package manager. It has
 a number of variations:

 {{{
 emerge foo
 }}}

 means install or re-install package foo. So if a newer one is available,
 that newer one will be installed. This is the behaviur that bugs #168 &
 #198 are asking for. If foo is already installed and no later version is
 available then it is re-installed. The default behavior is not to upgrade
 dependencies of foo even if updates are available, that is we
 install/upgrade the minimum number of packages necessary to install the
 package requested.

 {{{
 emerge foo --update
 }}}

 changes the behavior so that foo is not re-installed if it is already
 installed. Remember the default behavior was to reinstall foo if it was
 the latest version.

 This is probably the most controversial behasvour. It'd make a lot of
 sense to reverse the default of this mode and make --update the default
 and have something like --force-reinstall to re-install the same version
 that is already installed.

 {{{
 emerge foo --deep
 }}}

 This modifies the behaviour to also update dependencies. So this updates
 the maximal number of packages that are used directly or indirectly by
 package foo.

 There are also a couple meta-packages. One emerge world which is all
 packages that have ever been explicitly requested (ie not including
 packages that were merely dependencies of requested packages). That detail
 is probably not necessary, but we could do with an everything target.

 So in this gentoo semantics, we'd express the new upgrade command by
 {{{
 emerge world --update --deep
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/198#comment:3>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects