[GHC] #10643: GHC cannot import submodules when run from subfolder

[GHC]

#10643: GHC cannot import submodules when run from subfolder
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        Reporter:  FPtje             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:  subfolder
Operating System:  Unknown/Multiple  |  import submodule cd
 Type of failure:  GHC rejects       |            Architecture:
  valid program                      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by svenpanne):

 I think the point where we disagree is what you call the ''"-i problem"'':
 For me it's not a problem at all, it's as easy as it gets without being
 too clever and confusing, and it's standard behavior (compare with e.g.
 C/C++'s include path handling). And ''"ghc is arbitrarily restricted to
 run from the root of the source directory"'' is not correct, either: It is
 just the case (again standard behavior) that the default search path just
 contains "."
 (https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/separate-
 compilation.html#search-path).

 Regarding finding wrong modules: Extend your example

    Yes/A.hs     (containing module Yes.A)
    Yes/B.hs     (containing module Yes.b)

 with

    Yes/Yes/B.hs (containing module Yes.Yes.B)

 With your proposal when your cwd is the top-level "Yes", "ghc A.hs" would
 pick up the file containing Yes.Yes.B, which is not what you want,
 although it's in the perfectly right location. Another problem is: No
 build system of any kind should blindly go upwards in the directory
 hierarchy because of symbolic links, only downwards.

 And finally: In any non-toy program, having a single -i option is your
 least problem, so you will have a .cabal file, anyway.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10643#comment:5>
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