[GHC] #14648: ghc-pkg does handle unitids

[GHC]

#14648: ghc-pkg does handle unitids
-------------------------------------+-------------------------------------
           Reporter:  lspitzner      |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  ghc-pkg        |           Version:  8.2.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 I base the summary and the description on a single observation, see below.
 Sorry should this turn out to be a deduction too aggressive.

 == Assumed problem description

 New-style package-dbs can contain the same (package, version) entry
 multiple times, as entries are identified using an additional hash. I'll
 call the full identifier "unitId". The ghc-pkg interface seems to not
 support specifying full unitIds, i.e. "my-package-0.1.0.0-somehash" seems
 to be interpreted like "my-package-0.1.0.0-*". This is both a missing
 functionality and a bug:

 1. many operations make sense per-unitId, not just per (package, version)
 2. The fact that my-package-0.1.0.0-otherhash is unregistered by "ghc-pkg
 unregister my-package-0.1.0.0-somehash" is quite surprising.

 == Observation

 1. Take a package-db containing the same (package, version) entry with two
 different hashes, e.g.
   -
 semigroupoids-5.2.1-2f552e489ce3109c2672606e2dc6e33c4f38174da930d5db0bb0dafbb4dccae8
   -
 semigroupoids-5.2.1-e50d44ead36c6b8428c9417007cee15bd9cbe3a2906c19553366d94b15c2471e

   I suggest making a copy of some existing (cabal store) db.

 2. call `ghc-pkg --package-db my-copy unregister
 semigroupoids-5.2.1-2f552e489ce3109c2672606e2dc6e33c4f38174da930d5db0bb0dafbb4dccae8`

 3. test `ghc-pkg --package-db my-copy list semigroupoids-5.2.1`

 Expected result: `semigroupoids-5.2.1-e50d44ea..` is still registered

 Observed result: empty list

 == Impact

 This blocks the use-case of a garbage-collection for the global new-style
 package db "store".

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14648>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler