[GHC] #4900: DEPENDS pragma

[GHC]

#4900: DEPENDS pragma
---------------------------------+------------------------------------------
    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
---------------------------------+------------------------------------------

Comment(by simonpj):

 Talking to Simon we understand the following language extensions:
  * A `{-# DEPENDS "foo" #-}` pragma
  * A TH function `addDependentFile`

 These would support two somewhat separate features:
  1. `ghc -M` would generate dependencies based on
     * `import` declarations (as now)
     * `{-# DEPENDS "foo" #-}` pragmas
     * `#line` pragamas generated by CPP

  2.  The `ghc` recompilation check (which skips compilation when nothing
 has changed) would take account of
     * `import` declarations
     * `{-# DEPENDS "foo" #-}` pragmas
     * `#line` pragamas generated by CPP
     * `addDependentFile` calls produced in the previous compilation

 Note that (1) and (2) are not identical... `ghc -M` can't run TH to see
 what `addDependentFile` calls it makes.

 So this is not entirely satisfactory, but perhaps useful enough to be
 worth doing.  If anyone wants to volunteer -- it's not too hard.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4900#comment:15>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler