From aca843ed3ff90409d216d9da2a3be961533bc513 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Fri, 19 May 2017 16:07:30 -0400
Subject: [PATCH] Add some combinators for working with SGR codes.

---
 src/Data/Syntax/Assignment.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Data/Syntax/Assignment.hs b/src/Data/Syntax/Assignment.hs
index af5a4fcfc..de43a7a82 100644
--- a/src/Data/Syntax/Assignment.hs
+++ b/src/Data/Syntax/Assignment.hs
@@ -167,7 +167,7 @@ data ErrorCause symbol
 -- | Pretty-print an Error with reference to the source where it occurred.
 showError :: Show symbol => Source.Source -> Error symbol -> ShowS
 showError source Error{..}
-  = showSourcePos errorPos . showString ": " . showString (setSGRCode [SetColor Foreground Vivid Red]) . showString "error" . showString (setSGRCode []) . showString ": " . showExpectation . showChar '\n'
+  = showSourcePos errorPos . showString ": " . withSGRCode [SetColor Foreground Vivid Red] "error" . showString ": " . showExpectation . showChar '\n'
   . showString context -- actualLines results include line endings, so no newline here
   . showString (replicate (succ (Info.column errorPos + lineNumberDigits)) ' ') . showChar '^' . showChar '\n'
   . showString (prettyCallStack callStack) . showChar '\n'
@@ -179,6 +179,8 @@ showError source Error{..}
         context = maybe "\n" (toS . Source.sourceText . sconcat) (nonEmpty [ Source.Source (toS (showLineNumber i)) <> Source.Source ": " <> l | (i, l) <- zip [1..] (Source.actualLines source), inRange (Info.line errorPos - 2, Info.line errorPos) i ])
         showLineNumber n = let s = show n in replicate (lineNumberDigits - length s) ' ' <> s
         lineNumberDigits = succ (floor (logBase 10 (fromIntegral (Info.line errorPos) :: Double)))
+        showSGRCode = showString . setSGRCode
+        withSGRCode code string = showSGRCode code . showString string . showSGRCode []
 
 showSymbols :: Show symbol => [symbol] -> ShowS
 showSymbols [] = showString "end of input nodes"