[GHC] #15858: Enabling a pure Plugin with existing build output never triggers recompilation

[GHC]

#15858: Enabling a pure Plugin with existing build output never triggers
recompilation
-------------------------------------+-------------------------------------
        Reporter:  DanielG           |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.7
      Resolution:                    |             Keywords:  Plugins
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5299
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"efb6a30f0b70948ba51497bf2831e009ec6e1378/ghc"
 efb6a30f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="efb6a30f0b70948ba51497bf2831e009ec6e1378"
 Fix recompilation checking of pure plugins

 Previously when switching from using a Plugin with
 `RecompMaybe`/`ForceRecompile` in `pluginRecompile` to a Plugin with
 `NoForceRecompile` GHC would never even consider recompiling.

 However the previously active plugin could have modified the
 compilation output so we should recompile.

 Test Plan: validate

 Reviewers: bgamari, mpickering

 Subscribers: mpickering, rwbarton, carter

 GHC Trac Issues: #15858

 Differential Revision: https://phabricator.haskell.org/D5299
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15858#comment:4>
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