[GHC] #4900: DEPENDS pragma

[GHC]

#4900: DEPENDS pragma
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    Reporter:  cdsmith           |        Owner:              
        Type:  feature request   |       Status:  new         
    Priority:  normal            |    Milestone:  7.4.1       
   Component:  Build System      |      Version:              
    Keywords:                    |     Testcase:              
   Blockedby:                    |   Difficulty:              
          Os:  Unknown/Multiple  |     Blocking:              
Architecture:  Unknown/Multiple  |      Failure:  None/Unknown
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Comment(by simonmar):

 Note that the `DEPENDS` pragma idea in this ticket is better than an
 `addDependentFile` function in TH, for two reasons:

  - `ghc -M` could emit these dependencies, because we only need to read
 the pragma, not compile the module
  - Cabal and other external tools will never be able to track these
 dependencies.  There are plans to do this in Cabal in the future, and
 `addDependentFile` would just not work there.

 `DEPENDS` is not nearly as nice as `addDependentFile`, but if we want to
 be able to do dependency analysis without compiling code, I think we have
 to stick with `DEPENDS`.  We could still have a `checkDependentFile` that
 would emit a warning if you had forgotten the `DEPENDS` pragma.

 Another design question is whether the filename is relative or absolute -
 do we resolve it to an absolute name at compile time?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4900#comment:10>
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