[GHC] #11069: :cd in GHCi unloads modules

[GHC]

#11069: :cd in GHCi unloads modules
-------------------------------------+-------------------------------------
           Reporter:  mgsloan        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:
          Component:  GHCi           |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Other
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 If I run `stack ghci` in the [https://github.com/commercialhaskell/stack
 stack] repo, and then use `:cd`, I get the following:

 > Warning: changing directory causes all loaded modules to be unloaded,
 > because the search path has changed.

 And, indeed, all modules are unloaded.  What's particularly strange about
 this is that in my case all of the paths provided on the commandline are
 absolute.  Here's the output of ":show paths":

 > current working directory:
 >
 >  /home/mgsloan/fpco/stack
 >
 > module import search paths:
 >
 >  /home/mgsloan/fpco/stack/src
 >
 >  /home/mgsloan/fpco/stack/.stack-
 work/dist/x86_64-linux/Cabal-1.22.4.0/build/autogen
 >
 >  /home/mgsloan/fpco/stack/.stack-
 work/dist/x86_64-linux/Cabal-1.22.4.0/build
 >
 >  /home/mgsloan/fpco/stack/src/main

 How about removing any dependency in GHC on the current working directory,
 and instead store it when the session is initialized?

 This is also necessary if we want to support per-package working
 directories,
 [https://ghc.haskell.org/trac/ghc/timeline?from=2015-11-08T06%3A17%3A58Z&precision=second
 details here].

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11069>
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