Fix escaping of `-` in ms writer.

In 5132f1ef330d3eb2a0bf87037035beaeaf19d3f3 we added `-` to
the list of characters needing backslash escaping, to accommodate
a change in groff man's behavior, described here:
https://lwn.net/Articles/947941/

This change also led `-` to be escaped in ms output, but that
is wrong; `\-` in ms is a unicode minus sign.

To fix this, we add a Boolean parameter to `escapeString` in
Text.Pandoc.Writers.Roff that determines whether `-` is to
be escaped.  (NB: This is not an exported function in the API.)

The list `standardEscapes` in Text.Pandoc.RoffChar no longer
contains `-`.

Closes #10536.

4 files changed, 12 insertions, 8 deletions

diff --git a/src/Text/Pandoc/RoffChar.hs b/src/Text/Pandoc/RoffChar.hs
index feeca2ca3..f5a4134a1 100644
--- a/src/Text/Pandoc/RoffChar.hs
+++ b/src/Text/Pandoc/RoffChar.hs
@@ -34,7 +34,6 @@ standardEscapes =
   , ('`', "\\[ga]")
   , ('^', "\\[ha]")
   , ('~', "\\[ti]")
-  , ('-', "\\-")
   , ('\\', "\\[rs]")
   , ('@', "\\[at]") -- because we use @ as a table and math delimiter
   , ('\x2026', "\\&...")  -- because u2026 doesn't render on tty
diff --git a/src/Text/Pandoc/Writers/Man.hs b/src/Text/Pandoc/Writers/Man.hs
index 3adf15043..e43caa6e4 100644
--- a/src/Text/Pandoc/Writers/Man.hs
+++ b/src/Text/Pandoc/Writers/Man.hs
@@ -86,9 +86,9 @@ pandocToMan opts (Pandoc meta blocks) = do
        Just tpl -> renderTemplate tpl context
 
 escString :: WriterOptions -> Text -> Text
-escString opts = escapeString (if writerPreferAscii opts
-                                  then AsciiOnly
-                                  else AllowUTF8)
+escString opts = escapeString True (if writerPreferAscii opts
+                                       then AsciiOnly
+                                       else AllowUTF8)
 
 -- | Return man representation of notes.
 notesToMan :: PandocMonad m => WriterOptions -> [[Block]] -> StateT WriterState m (Doc Text)
diff --git a/src/Text/Pandoc/Writers/Ms.hs b/src/Text/Pandoc/Writers/Ms.hs
index dc7fb91fe..e2c97044f 100644
--- a/src/Text/Pandoc/Writers/Ms.hs
+++ b/src/Text/Pandoc/Writers/Ms.hs
@@ -92,7 +92,7 @@ pandocToMs opts (Pandoc meta blocks) = do
 
 escapeStr :: WriterOptions -> Text -> Text
 escapeStr opts =
-  escapeString (if writerPreferAscii opts then AsciiOnly else AllowUTF8)
+  escapeString False (if writerPreferAscii opts then AsciiOnly else AllowUTF8)
 
 -- In PDFs we need to escape parentheses and backslash.
 -- In PDF we need to encode as UTF-16 BE.
diff --git a/src/Text/Pandoc/Writers/Roff.hs b/src/Text/Pandoc/Writers/Roff.hs
index 989c02826..9a891b7a1 100644
--- a/src/Text/Pandoc/Writers/Roff.hs
+++ b/src/Text/Pandoc/Writers/Roff.hs
@@ -74,13 +74,18 @@ combiningAccentsMap = Map.fromList combiningAccents
 essentialEscapes :: Map.Map Char Text
 essentialEscapes = Map.fromList standardEscapes
 
--- | Escape special characters for roff.
-escapeString :: EscapeMode -> Text -> Text
-escapeString e = Text.concat . escapeString' e . Text.unpack
+-- | Escape special characters for roff. If the first parameter is
+-- True, escape @-@ as @\-@, as required by current versions of groff man;
+-- otherwise leave it unescaped, as neededfor ms.
+escapeString :: Bool -> EscapeMode -> Text -> Text
+escapeString escapeHyphen e = Text.concat . escapeString' e . Text.unpack
   where
     escapeString' _ [] = []
     escapeString' escapeMode ('\n':'.':xs) =
       "\n\\&." : escapeString' escapeMode xs
+    -- see #10533; we need to escape hyphens as \- in man but not in ms:
+    escapeString' escapeMode ('-':xs) | escapeHyphen =
+      "\\-" : escapeString' escapeMode xs
     escapeString' escapeMode (x:xs) =
       case Map.lookup x essentialEscapes of
         Just s  -> s : escapeString' escapeMode xs