[commit: ghc] master: Fix recompilation checking of pure plugins (efb6a30)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/efb6a30f0b70948ba51497bf2831e009ec6e1378/ghc

>---------------------------------------------------------------

commit efb6a30f0b70948ba51497bf2831e009ec6e1378
Author: Daniel Gröber <dxld at darkboxed.org>
Date:   Tue Dec 11 18:36:00 2018 -0500

    Fix recompilation checking of pure plugins
    
    Previously when switching from using a Plugin with
    `RecompMaybe`/`ForceRecompile` in `pluginRecompile` to a Plugin with
    `NoForceRecompile` GHC would never even consider recompiling.
    
    However the previously active plugin could have modified the
    compilation output so we should recompile.
    
    Test Plan: validate
    
    Reviewers: bgamari, mpickering
    
    Subscribers: mpickering, rwbarton, carter
    
    GHC Trac Issues: #15858
    
    Differential Revision: https://phabricator.haskell.org/D5299


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efb6a30f0b70948ba51497bf2831e009ec6e1378
 compiler/iface/MkIface.hs             | 59 ++++++++++++++++++++++++++++-------
 compiler/main/DynFlags.hs             |  7 +++++
 docs/users_guide/extending_ghc.rst    | 19 ++++++++---
 testsuite/tests/plugins/T15858.script | 33 ++++++++++++++++++++
 testsuite/tests/plugins/T15858.stderr | 21 +++++++++++++
 testsuite/tests/plugins/all.T         |  8 +++++
 6 files changed, 132 insertions(+), 15 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc efb6a30f0b70948ba51497bf2831e009ec6e1378