Markdown writer: update escaping rules for \.

We now escape `\` only if `raw_tex` is enabled or
it is followed by a non-alphanumeric.

src/Text/Pandoc/Writers/Markdown/Inline.hs

@@ -68,8 +68,16 @@ escapeText opts = T.pack . go' . T.unpack
   go [] = []
   go (c:cs) =
     case c of
-       _ | c `elem` ['\\','`','*','_','[',']'] ->
-              '\\':c:go cs
+       '[' -> '\\':c:go cs
+       ']' -> '\\':c:go cs
+       '`' -> '\\':c:go cs
+       '*' -> '\\':c:go cs
+       '_' -> '\\':c:go cs
+       '\\' | isEnabled Ext_raw_tex opts -> '\\':c:go cs
+            | otherwise ->
+              case cs of -- don't escape \ if we don't have to:
+                d:_ | isAlphaNum d -> c:go cs
+                _ -> '\\':c:go cs
        '>' | isEnabled Ext_all_symbols_escapable opts -> '\\':'>':go cs
            | otherwise -> ">" ++ go cs
        '<' | isEnabled Ext_all_symbols_escapable opts -> '\\':'<':go cs

test/command/4527.md

@@ -1,24 +1,11 @@
-# Raw TeX blocks in CommonMark with and without raw_tex
-
+This command comes through as regular text:
 ```
-% pandoc -f latex+raw_tex -t commonmark-raw_tex
-\someunknowncommand
-
-Hello.
+% pandoc -f latex+raw_tex -t native
+\maketitle
 ^D
-Hello.
+[ RawBlock (Format "latex") "\\maketitle" ]
 ```
 
-```
-% pandoc -f latex+raw_tex -t commonmark+raw_tex
-\someunknowncommand
-
-Hello.
-^D
-\someunknowncommand
-
-Hello.
-```
 
 ```
 % pandoc -f latex -t native

test/writer.opml

@@ -50,7 +50,7 @@
 </outline>
 <outline text="Smart quotes, ellipses, dashes" _note="“Hello,” said the spider. “‘Shelob’ is my name.”&#10;&#10;‘A’, ‘B’, and ‘C’ are letters.&#10;&#10;‘Oak,’ ‘elm,’ and ‘beech’ are names of trees. So is ‘pine.’&#10;&#10;‘He said, “I want to go.”’ Were you alive in the 70’s?&#10;&#10;Here is some quoted ‘`code`’ and a “[quoted&#10;link](http://example.com/?foo=1&amp;bar=2)”.&#10;&#10;Some dashes: one—two — three—four — five.&#10;&#10;Dashes between numbers: 5–7, 255–66, 1987–1999.&#10;&#10;Ellipses…and…and….&#10;&#10;------------------------------------------------------------------------">
 </outline>
-<outline text="LaTeX" _note="-   &#10;-   2 + 2 = 4&#10;-   *x* ∈ *y*&#10;-   *α* ∧ *ω*&#10;-   223&#10;-   *p*-Tree&#10;-   Here’s some display math:&#10;    $$\\frac{d}{dx}f(x)=\\lim\_{h\\to 0}\\frac{f(x+h)-f(x)}{h}$$&#10;-   Here’s one that has a line break in it: *α* + *ω* × *x*².&#10;&#10;These shouldn’t be math:&#10;&#10;-   To get the famous equation, write `$e = mc^2$`.&#10;-   $22,000 is a *lot* of money. So is $34,000. (It worked if “lot” is&#10;    emphasized.)&#10;-   Shoes ($20) and socks ($5).&#10;-   Escaped `$`: $73 *this should be emphasized* 23$.&#10;&#10;Here’s a LaTeX table:&#10;&#10;------------------------------------------------------------------------">
+<outline text="LaTeX" _note="-   &#10;-   2 + 2 = 4&#10;-   *x* ∈ *y*&#10;-   *α* ∧ *ω*&#10;-   223&#10;-   *p*-Tree&#10;-   Here’s some display math:&#10;    $$\frac{d}{dx}f(x)=\lim\_{h\to 0}\frac{f(x+h)-f(x)}{h}$$&#10;-   Here’s one that has a line break in it: *α* + *ω* × *x*².&#10;&#10;These shouldn’t be math:&#10;&#10;-   To get the famous equation, write `$e = mc^2$`.&#10;-   $22,000 is a *lot* of money. So is $34,000. (It worked if “lot” is&#10;    emphasized.)&#10;-   Shoes ($20) and socks ($5).&#10;-   Escaped `$`: $73 *this should be emphasized* 23$.&#10;&#10;Here’s a LaTeX table:&#10;&#10;------------------------------------------------------------------------">
 </outline>
 <outline text="Special Characters" _note="Here is some unicode:&#10;&#10;-   I hat: Î&#10;-   o umlaut: ö&#10;-   section: §&#10;-   set membership: ∈&#10;-   copyright: ©&#10;&#10;AT&amp;T has an ampersand in their name.&#10;&#10;AT&amp;T is another way to write it.&#10;&#10;This &amp; that.&#10;&#10;4 &amp;lt; 5.&#10;&#10;6 &amp;gt; 5.&#10;&#10;Backslash: \\&#10;&#10;Backtick: \`&#10;&#10;Asterisk: \*&#10;&#10;Underscore: \_&#10;&#10;Left brace: {&#10;&#10;Right brace: }&#10;&#10;Left bracket: \[&#10;&#10;Right bracket: \]&#10;&#10;Left paren: (&#10;&#10;Right paren: )&#10;&#10;Greater-than: &amp;gt;&#10;&#10;Hash: \#&#10;&#10;Period: .&#10;&#10;Bang: !&#10;&#10;Plus: +&#10;&#10;Minus: -&#10;&#10;------------------------------------------------------------------------">
 </outline>