Allow Fourmolu 0.12 (#3565)

* Allow Fourmolu 0.12

* Bump index-state

This allows us to pick up Fourmolu 0.12.

* Enable Fourmolu plugin on GHC 9.6

Author: georgefst

cabal.project

@@ -55,7 +55,7 @@ package *
 
 write-ghc-environment-files: never
 
-index-state: 2023-03-30T00:00:00Z
+index-state: 2023-04-19T12:00:00Z
 
 constraints:
   -- For GHC 9.4, older versions of entropy fail to build on Windows

haskell-language-server.cabal

@@ -334,7 +334,7 @@ common floskell
     cpp-options: -Dhls_floskell
 
 common fourmolu
-  if flag(fourmolu) && impl(ghc < 9.5)
+  if flag(fourmolu)
     build-depends: hls-fourmolu-plugin ^>= 1.1
     cpp-options: -Dhls_fourmolu
 

plugins/hls-fourmolu-plugin/hls-fourmolu-plugin.cabal

@@ -23,8 +23,7 @@ source-repository head
   location: git://github.com/haskell/haskell-language-server.git
 
 library
-  if impl(ghc >= 9.5)
-    buildable: False
+  buildable: True
   exposed-modules:
       Ide.Plugin.Fourmolu
     , Ide.Plugin.Fourmolu.Shim
@@ -33,7 +32,7 @@ library
   build-depends:
     , base            >=4.12 && <5
     , filepath
-    , fourmolu        ^>=0.3 || ^>=0.4 || ^>= 0.6 || ^>= 0.7 || ^>= 0.8 || ^>= 0.9 || ^>= 0.10 || ^>= 0.11
+    , fourmolu        ^>=0.3 || ^>=0.4 || ^>= 0.6 || ^>= 0.7 || ^>= 0.8 || ^>= 0.9 || ^>= 0.10 || ^>= 0.11 || ^>= 0.12
     , ghc
     , ghc-boot-th
     , ghcide          ^>= 1.9 || ^>= 1.10
@@ -49,8 +48,7 @@ library
   default-language: Haskell2010
 
 test-suite tests
-  if impl(ghc >= 9.5)
-    buildable: False
+  buildable: True
   type:             exitcode-stdio-1.0
   default-language: Haskell2010
   hs-source-dirs:   test