Stop showing ANSI codes on unix-based OSes

cc @jvoigtlaender

I thought that displayIO was for ANSI and displayS was for not-ANSI. It
turns out that displayS will add the ANSI codes into the string if you
are on not-Windows. This meant that garbage characters were ending up
in the output of JSON errors or reactor errors

@rtfeldman, I’ll try to get a new set of binaries ready for linux
32-bit and mac

src/Reporting/Report.hs

@@ -13,7 +13,8 @@ import Data.Aeson ((.=))
 import qualified Data.Aeson.Types as Json
 import System.IO (Handle)
 import Text.PrettyPrint.ANSI.Leijen
-    ( Doc, (<>), displayS, displayIO, dullcyan, fillSep, hardline, renderPretty, text
+    ( Doc, SimpleDoc(..), (<>), displayS, displayIO, dullcyan, fillSep
+    , hardline, renderPretty, text
     )
 
 import qualified Reporting.Region as R
@@ -83,15 +84,38 @@ messageBar tag location =
 -- RENDER DOCS
 
 
+toHandle :: Handle -> String -> R.Region -> Report -> String -> IO ()
+toHandle handle location region rprt source =
+  displayIO
+    handle
+    (renderPretty 1 80 (toDoc location region rprt source))
+
+
 toString :: String -> R.Region -> Report -> String -> String
 toString location region rprt source =
   displayS
-    (renderPretty 1 80 (toDoc location region rprt source))
+    (stripAnsi (renderPretty 1 80 (toDoc location region rprt source)))
     ""
 
 
-toHandle :: Handle -> String -> R.Region -> Report -> String -> IO ()
-toHandle handle location region rprt source =
-  displayIO
-    handle
-    (renderPretty 1 80 (toDoc location region rprt source))
+stripAnsi :: SimpleDoc -> SimpleDoc
+stripAnsi simpleDoc =
+  case simpleDoc of
+    SFail ->
+      SFail
+
+    SEmpty ->
+      SEmpty
+
+    SChar chr subDoc ->
+      SChar chr (stripAnsi subDoc)
+
+    SText n str subDoc ->
+      SText n str (stripAnsi subDoc)
+
+    SLine n subDoc ->
+      SLine n (stripAnsi subDoc)
+
+    SSGR _ subDoc ->
+      stripAnsi subDoc
+