[GHC] #15234: WARNING in hptSomeThingsBelowUs when using a source plugin

[GHC]

#15234: WARNING in hptSomeThingsBelowUs when using a source plugin
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        Reporter:  mpickering        |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:  fixed             |             Keywords:
                                     |  SourcePlugins, plugins
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4937
       Wiki Page:                    |
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Comment (by sheaf):

 I'm sure this isn't news to anyone, but after testing I can confirm that
 plugins work on GHC 8.6.1 on Windows if one bypasses the test for whether
 a plugin has changed (`mkPluginUsage` in `DsUsage.hs`).

 So it seems the solution should be to make the functions that look up
 plugin locations, within `mkPluginUsage`, work correctly on Windows.

 The only relevant files that I can see on my machine are static `.a`
 files. For instance, instead of the non-existent `libHSghc-
 typelits-_-0.6.2-faf29727b3dbdfa09cfb6f0c881a2a227b5d2bb0-ghc8.6.1.dll`, I
 have `libHSghc-
 typelits-_-0.6.2-faf29727b3dbdfa09cfb6f0c881a2a227b5d2bb0.a`, which I have
 to assume is what is being used by GHC for plugin usage. \\
 Does this mean mkPluginUsage should be hashing these files instead? On
 Windows only?

 The attached `DsUsage.hs` file is working on my end, inelegant as it may
 be. It tries looking for .a files if looking for dynamic files (.dll, .so,
 .dylib) fails.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15234#comment:12>
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