[GHC] #16318: Explicitly passing -package-env causes "Loaded package environment from .ghc.environment" message to be printed twice

[GHC]

#16318: Explicitly passing -package-env causes "Loaded package environment from
.ghc.environment" message to be printed twice
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I'm reasonably confident that commit
 e67bebbf735db498c2cbf191d1878644ca5ed5cc (`Load plugins in interactive
 session`) is the culprit:

 {{{#!diff
 -ghciUI :: [(FilePath, Maybe Phase)] -> Maybe [String] -> Ghc ()
 +ghciUI :: HscEnv -> DynFlags -> [(FilePath, Maybe Phase)] -> Maybe
 [String]
 +       -> Ghc ()
  #if !defined(GHCI)
 -ghciUI _ _ = throwGhcException (CmdLineError "not built for interactive
 use")
 +ghciUI _ _ _ _ =
 +  throwGhcException (CmdLineError "not built for interactive use")
  #else
 -ghciUI     = interactiveUI defaultGhciSettings
 +ghciUI hsc_env dflags0 srcs maybe_expr = do
 +  dflags1 <- liftIO (initializePlugins hsc_env dflags0)
 +  _ <- GHC.setSessionDynFlags dflags1
 +  interactiveUI defaultGhciSettings srcs maybe_expr
  #endif
 }}}

 This inserts a call to `setSessionDynFlags`, which transitively invokes
 `initPackages`, which is the function that logs the "`Loaded package
 environment from ...`" message. But if you look at the source code for
 `interactiveUI`, you'll see that it invokes `setProgramDynFlags`, which
 //itself// transitively invokes `initPackages`!

 It seems like we might want to decouple the action of logging package
 environments from `initPackages`. Thoughts, hvr?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16318#comment:2>
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