Improve Markdown writer escaping.

This fixes escaping for '#' in particular.
Closes #7726.

7 files changed, 46 insertions, 23 deletions

diff --git a/src/Text/Pandoc/Writers/Markdown/Inline.hs b/src/Text/Pandoc/Writers/Markdown/Inline.hs
index be22f8d9f..e774b5cc4 100644
--- a/src/Text/Pandoc/Writers/Markdown/Inline.hs
+++ b/src/Text/Pandoc/Writers/Markdown/Inline.hs
@@ -44,32 +44,35 @@ import Text.Pandoc.Writers.Markdown.Types (MarkdownVariant(..),
 
 -- | Escape special characters for Markdown.
 escapeText :: WriterOptions -> Text -> Text
-escapeText opts = T.pack . go . T.unpack
+escapeText opts = T.pack . go' . T.unpack
  where
   startsWithSpace (' ':_) = True
   startsWithSpace ('\t':_) = True
   startsWithSpace [] = True
   startsWithSpace _ = False
+  go' ('#':cs)
+    | isEnabled Ext_space_in_atx_header opts
+    = if startsWithSpace (dropWhile (=='#') cs)
+         then '\\':'#':go cs
+         else '#':go cs
+    | otherwise = '\\':'#':go cs
+  go' ('@':cs)
+    | isEnabled Ext_citations opts =
+        case cs of
+             (d:_)
+               | isAlphaNum d || d == '_' || d == '{'
+                  -> '\\':'@':go cs
+             _ -> '@':go cs
+  go' cs = go cs
   go [] = []
   go (c:cs) =
     case c of
-       '<' | isEnabled Ext_all_symbols_escapable opts ->
-              '\\' : '<' : go cs
-           | otherwise -> "&lt;" ++ go cs
-       '>' | isEnabled Ext_all_symbols_escapable opts ->
-              '\\' : '>' : go cs
-           | otherwise -> "&gt;" ++ go cs
-       '@' | isEnabled Ext_citations opts ->
-               case cs of
-                    (d:_)
-                      | isAlphaNum d || d == '_' || d == '{'
-                         -> '\\':'@':go cs
-                    _ -> '@':go cs
-       '#' | isEnabled Ext_space_in_atx_header opts
-           , startsWithSpace cs
-           -> '\\':'#':go cs
        _ | c `elem` ['\\','`','*','_','[',']'] ->
               '\\':c:go cs
+       '>' | isEnabled Ext_all_symbols_escapable opts -> '\\':'>':go cs
+           | otherwise -> "&gt;" ++ go cs
+       '<' | isEnabled Ext_all_symbols_escapable opts -> '\\':'<':go cs
+           | otherwise -> "&lt;" ++ go cs
        '|' | isEnabled Ext_pipe_tables opts -> '\\':'|':go cs
        '^' | isEnabled Ext_superscript opts -> '\\':'^':go cs
        '~' | isEnabled Ext_subscript opts ||
@@ -90,8 +93,6 @@ escapeText opts = T.pack . go . T.unpack
                   | isEnabled Ext_intraword_underscores opts
                   , isAlphaNum c
                   , isAlphaNum x -> c : '_' : x : go xs
-                '#':xs           -> c : '#' : go xs
-                '>':xs           -> c : '>' : go xs
                 _                -> c : go cs
 
 attrsToMarkdown :: Attr -> Doc Text
diff --git a/test/command/3792.md b/test/command/3792.md
index eff26d517..eb109b9cc 100644
--- a/test/command/3792.md
+++ b/test/command/3792.md
@@ -6,7 +6,7 @@ and properly escaped.
 ok
 ^D
 ---
-title: \<this> \*that\*
+title: \<this\> \*that\*
 ---
 
 ok
diff --git a/test/command/4164.md b/test/command/4164.md
index 68cbd0584..4e7b7e285 100644
--- a/test/command/4164.md
+++ b/test/command/4164.md
@@ -26,6 +26,6 @@ Here is inline html:
 
 Here is inline html:
 
-\<div> \<balise> bla bla \</div>
+\<div\> \<balise\> bla bla \</div\>
 
 ```
diff --git a/test/command/7208.md b/test/command/7208.md
index fe02ec32e..e65943ade 100644
--- a/test/command/7208.md
+++ b/test/command/7208.md
@@ -2,5 +2,5 @@
 % pandoc -t gfm
 \<hi\>
 ^D
-\<hi>
+\<hi\>
 ```
diff --git a/test/command/7726.md b/test/command/7726.md
new file mode 100644
index 000000000..bab11ca04
--- /dev/null
+++ b/test/command/7726.md
@@ -0,0 +1,22 @@
+```
+% pandoc -t markdown
+\# Hi
+
+\## Hi
+
+\### Hi
+
+\#### hi
+
+and #hi
+^D
+\# Hi
+
+\## Hi
+
+\### Hi
+
+\#### hi
+
+and #hi
+```
diff --git a/test/command/biblatex-sigfridsson.md b/test/command/biblatex-sigfridsson.md
index e042a8762..f83c35622 100644
--- a/test/command/biblatex-sigfridsson.md
+++ b/test/command/biblatex-sigfridsson.md
@@ -90,7 +90,7 @@ references:
   - family: Ryde
     given: Ulf
   container-title: Journal of Computational Chemistry
-  doi: "10.1002/(SICI)1096-987X(199803)19:4\\<377::AID-JCC1>3.0.CO;2-P"
+  doi: "10.1002/(SICI)1096-987X(199803)19:4\\<377::AID-JCC1\\>3.0.CO;2-P"
   id: sigfridsson
   issue: 4
   issued: 1998
diff --git a/test/writer.opml b/test/writer.opml
index bfe1e5de6..6bdcb882e 100644
--- a/test/writer.opml
+++ b/test/writer.opml
@@ -52,7 +52,7 @@
 </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>
-<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 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>
 <outline text="Links">
   <outline text="Explicit" _note="Just a [URL](/url/).&#10;&#10;[URL and title](/url/ &quot;title&quot;).&#10;&#10;[URL and title](/url/ &quot;title preceded by two spaces&quot;).&#10;&#10;[URL and title](/url/ &quot;title preceded by a tab&quot;).&#10;&#10;[URL and title](/url/ &quot;title with &quot;quotes&quot; in it&quot;)&#10;&#10;[URL and title](/url/ &quot;title with single quotes&quot;)&#10;&#10;[with\_underscore](/url/with_underscore)&#10;&#10;[Email link](mailto:nobody@nowhere.net)&#10;&#10;[Empty]().">