Add fix-stylish-haskell script (#444)

slightly adapted from plutus repo.

---------

Co-authored-by: Moritz Angermann <moritz.angermann@gmail.com>
Co-authored-by: Rodney Lorrimar <rodney.lorrimar@iohk.io>

default.nix

@@ -80,6 +80,7 @@ let
     inherit (import sources.cardano-repo-tool {inherit system;}) cardano-repo-tool;
     stack-cabal-sync-shell = pkgsDefault.callPackage ./pkgs/stack-cabal-sync-shell.nix { inherit cardano-repo-tool; };
     supervisord = pkgsDefault.callPackage ./supervisord {};
+    fixStylishHaskell = pkgsDefault.callPackage ./tests/fix-stylish-haskell.nix {};
 
     # Check scripts
     check-hydra = __trace "check-hydra is deprecated. Please use hydraEvalErrors" pkgsDefault.callPackage ./ci/check-hydra.nix {};
@@ -189,7 +190,8 @@ let
       checkCabalProject
       hydraEvalErrors
       checkRepoTagsOnMasterBranches
-      checkStackProject;
+      checkStackProject
+      fixStylishHaskell;
     release-lib = ./lib/release-lib.nix;
   };
 in self

tests/fix-stylish-haskell.nix

@@ -0,0 +1,17 @@
+{ writeScriptBin, git, fd, stylish-haskell }:
+
+writeScriptBin "fix-stylish-haskell" ''
+    ${git}/bin/git diff > pre-stylish.diff
+    ${fd}/bin/fd --extension hs "$@" \
+      --exec ${stylish-haskell}/bin/stylish-haskell -i {}
+    ${git}/bin/git diff > post-stylish.diff
+    diff pre-stylish.diff post-stylish.diff > /dev/null
+    if [ $? != 0 ]
+    then
+      echo "Changes by stylish have been made. Please commit them."
+    else
+      echo "No stylish changes were made."
+    fi
+    rm pre-stylish.diff post-stylish.diff
+    exit
+''

tests/stylish-haskell.nix

@@ -31,7 +31,7 @@ runCommand "stylish-check" {
     diff -ur orig stylish > $out/stylish.diff
     echo "file none $out/stylish.diff" > $out/nix-support/hydra-build-products
     echo "*** Stylish-haskell found changes that need addressed first"
-    echo "*** Please run \`nix-shell -A fixStylishHaskell\` and commit changes"
+    echo "*** Please run `$(nix-build ./nix -A iohkNix.fixStylishHaskell)/bin/fix-stylish-haskell --exclude '*/dist/*' --exclude '*/docs/*'` and commit changes"
     echo "*** or apply the diff generated by hydra if you don't have nix."
     exit $EXIT_CODE
   else