conditional support for haskeline, readline and editline

GF.cabal

@@ -543,10 +543,18 @@ data-files:
     lib/resource/thai/VerbTha.gf
     lib/LICENSE
 
+flag haskeline
+  Description: Enable Haskeline in the shell
+  Default:     True
+
 flag readline
   Description: Enable Readline in the shell
   Default:     True
 
+flag editline
+  Description: Enable Editline in the shell
+  Default:     True
+
 flag interrupt
   Description: Enable Ctrl+Break in the shell
   Default:     True
@@ -701,10 +709,20 @@ executable gf
     GFC
     GFI
 
+  if flag(haskeline)
+    build-depends: haskeline
+    cpp-options: -DUSE_HASKELINE
+    other-modules: GF.System.UseHaskeline
+  else
     if flag(readline)
       build-depends: readline
-    ghc-options: -DUSE_READLINE
+      cpp-options: -DUSE_READLINE
       other-modules: GF.System.UseReadline
+    else
+      if flag(editline)
+        build-depends: editline
+        cpp-options: -DUSE_EDITLINE
+        other-modules: GF.System.UseEditline
       else
         other-modules: GF.System.NoReadline
 

src/GF/System/Readline.hs

@@ -16,10 +16,18 @@
 
 module GF.System.Readline (fetchCommand, setCompletionFunction, filenameCompletionFunction) where
 
-#ifdef USE_READLINE
+#ifdef USE_HASKELINE
+
+import GF.System.UseHaskeline
+
+#elif USE_READLINE
 
 import GF.System.UseReadline
 
+#elif USE_EDITLINE
+
+import GF.System.UseEditline
+
 #else
 
 import GF.System.NoReadline