Package listing is duplicated when using `-Wunused-packages`
Summary
As per title.
Originally spotted here: https://github.com/tweag/rules_haskell/issues/1309
Steps to reproduce
CAT=cat
$CAT << EOF > test-package-env
package-id base-4.14.0.0
package-id containers-0.6.2.1
EOF
$CAT << EOF > Main.hs
module Main where
main = putStrLn "hello world"
EOF
ghc \
-Wunused-packages \
-package-env test-package-env \
Main.hs \
-main-is Main.main
Expected behavior
GHC fails with:
Loaded package environment from test-package-env
[1 of 1] Compiling Main ( Main.hs, Main.o )
Linking Main ...
<no location info>: warning: [-Wunused-packages]
The following packages were specified via -package or -package-id flags,
but were not needed for compilation:
- containers-0.6.2.1
Actual behavior
GHC fails with:
Loaded package environment from test-package-env
Loaded package environment from test-package-env
[1 of 1] Compiling Main ( Main.hs, Main.o )
Linking Main ...
<no location info>: warning: [-Wunused-packages]
The following packages were specified via -package or -package-id flags,
but were not needed for compilation:
- containers-0.6.2.1
- containers-0.6.2.1
Environment
- GHC version used: GHC 8.10.1
- GHC installed from Nixpkgs
- Full nix.shell environment from: https://github.com/tweag/rules_haskell/commit/82ace43c74f098f67def7cbbb485f2bd737c5c26
Optional:
-
Operating System:
-
System Architecture:
Linux nixos 4.19.94 #1 (closed)-NixOS SMP Thu Jan 9 09:19:10 UTC 2020 x86_64 GNU/Linux