From 3305a018bc38a435a7bd006f9447d97ee3ea6868 Mon Sep 17 00:00:00 2001
From: John MacFarlane <jgm@berkeley.edu>
Date: Tue, 30 Oct 2018 15:54:29 -0700
Subject: Roff reader: properly handle unknown backslash escapes.

They are treated as regular characters, according to groff 7.

Cloess #5034.
---
 src/Text/Pandoc/Readers/Roff.hs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/Text/Pandoc/Readers/Roff.hs b/src/Text/Pandoc/Readers/Roff.hs
index a540cc39d..9e3315cb3 100644
--- a/src/Text/Pandoc/Readers/Roff.hs
+++ b/src/Text/Pandoc/Readers/Roff.hs
@@ -284,7 +284,10 @@ escapeNormal = do
         CopyMode   -> char '\\'
         NormalMode -> return '\\'
       return [RoffStr "\\"]
-    _   -> fail $ "Unknown escape character \\" ++ [c]
+    _   -> return [RoffStr [c]]
+    -- man 7 groff: "If  a  backslash  is followed by a character that
+    -- does not constitute a defined escape sequence, the backslash
+    -- is  silently  ignored  and  the character maps to itself."
 
 escIgnore :: PandocMonad m
           => Char
-- 
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