[GHC] #14381: Consider making ghc-pkg fill in abi-depends based on depends

[GHC]

#14381: Consider making ghc-pkg fill in abi-depends based on depends
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        Reporter:  ezyang            |                Owner:  tdammers
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.4.2
       Component:  ghc-pkg           |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4159
       Wiki Page:                    |
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Comment (by tdammers):

 As discussed in person: this can produce a lot of warnings that may not be
 very useful in practice.

 `ghc-pkg` is essentially always doing the "right thing" here, overriding
 declared dependencies with inferred ones, and we are more confident on the
 inferred ones than the declared ones (the latter essentially being subject
 to human error).

 The way it works now, we will also see a lot of unnecessary warnings: when
 the declared and inferred dependencies agree, `ghc-pkg` will still do the
 overriding and issue a warning, but that warning will be pointless,
 because we aren't making any effective changes.

 Because of this, we will only raise this warning in debug mode, which
 should also take care of the now-failing tests.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14381#comment:11>
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