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| author | Matthew Pickering <matthewtpickering@gmail.com> | 2022-03-01 16:13:44 +0000 |
|---|---|---|
| committer | Matthew Pickering <matthewtpickering@gmail.com> | 2022-03-04 10:41:29 +0000 |
| commit | 7692da45af5f6e8f8b6bb0d55e2fe9d43779dc11 (patch) | |
| tree | 59de5c255e8b65e42e07fed17ec17360fb289e40 /docs | |
| parent | c534b3dd30de8d5a59ff64628a6a0b3eb938a102 (diff) | |
| download | haskell-wip/unused-package.tar.gz | |
Fix behaviour of -Wunused-packages in ghciwip/unused-package
Ticket #21110 points out that -Wunused-packages behaves a bit unusually
in GHCi. Now we define the semantics for -Wunused-packages in
interactive mode as follows:
* If you use -Wunused-packages on an initial load then the warning is reported.
* If you explicitly set -Wunused-packages on the command line then the
warning is displayed (until it is disabled)
* If you then subsequently modify the set of available targets by using
:load or :cd (:cd unloads everything) then the warning is (silently)
turned off.
This means that every :r the warning is printed if it's turned on (but you did ask for it).
Fixes #21110
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 5b0093b650..cad98bb4da 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -2083,7 +2083,7 @@ of ``-W(no-)*``. data Foo = Foo { f :: Int } | Bar .. ghc-flag:: -Wunused-packages - :shortdesc: warn when package is requested on command line, but was never loaded. + :shortdesc: warn when package is requested on command line, but not needed. :type: dynamic :reverse: -Wno-unused-packages :category: @@ -2092,11 +2092,15 @@ of ``-W(no-)*``. The option :ghc-flag:`-Wunused-packages` warns about packages, specified on command line via :ghc-flag:`-package ⟨pkg⟩` or - :ghc-flag:`-package-id ⟨unit-id⟩`, but were not loaded during compilation. - Usually it means that you have an unused dependency. + :ghc-flag:`-package-id ⟨unit-id⟩`, but were not needed during compilation. + If the warning fires it means the specified package wasn't needed for + compilation. + + This warning interacts poorly with GHCi because most invocations will pass + a large number of ``-package`` arguments on the initial load. Therefore if + you modify the targets using ``:load`` or ``:cd`` then the warning will be + silently disabled if it's enabled (see :ghc-ticket:`21110`). - You may want to enable this warning on a clean build or enable :ghc-flag:`-fforce-recomp` - in order to get reliable results. .. ghc-flag:: -Winvalid-haddock :shortdesc: warn when a Haddock comment occurs in an invalid position |