Markdown reader: added bracket syntax for native spans.

See #168.

Text.Pandoc.Options.Extension has a new constructor `Ext_brackted_spans`,
which is enabled by default in pandoc's Markdown.

MANUAL.txt

@@ -3063,6 +3063,16 @@ For example:
   is to look at the image resolution and the dpi metadata embedded in
   the image file.
 
+Spans
+-----
+
+#### Extension: `bracketed_spans` ####
+
+A bracketed sequence of inlines, as one would use to begin
+a link, will be treated as a span with attributes if it is
+followed immediately by attributes:
+
+    [This is *some text*]{.class key="val"}
 
 Footnotes
 ---------

src/Text/Pandoc/Options.hs

@@ -84,6 +84,7 @@ data Extension =
     | Ext_markdown_in_html_blocks -- ^ Interpret as markdown inside HTML blocks
     | Ext_native_divs             -- ^ Use Div blocks for contents of <div> tags
     | Ext_native_spans            -- ^ Use Span inlines for contents of <span>
+    | Ext_bracketed_spans         -- ^ Bracketed spans with attributes
     | Ext_markdown_attribute      -- ^ Interpret text inside HTML as markdown
                                   --   iff container has attribute 'markdown'
     | Ext_escaped_line_breaks     -- ^ Treat a backslash at EOL as linebreak
@@ -145,6 +146,7 @@ pandocExtensions = Set.fromList
   , Ext_markdown_in_html_blocks
   , Ext_native_divs
   , Ext_native_spans
+  , Ext_bracketed_spans
   , Ext_escaped_line_breaks
   , Ext_fancy_lists
   , Ext_startnum

src/Text/Pandoc/Readers/Markdown.hs

@@ -1482,6 +1482,7 @@ inline = choice [ whitespace
                 , strongOrEmph
                 , note
                 , cite
+                , bracketedSpan
                 , link
                 , image
                 , math
@@ -1750,6 +1751,13 @@ link = try $ do
   setState $ st{ stateAllowLinks = True }
   regLink B.linkWith lab <|> referenceLink B.linkWith (lab,raw)
 
+bracketedSpan :: MarkdownParser (F Inlines)
+bracketedSpan = try $ do
+  guardEnabled Ext_bracketed_spans
+  (lab,_) <- reference
+  attr <- attributes
+  return $ B.spanWith attr <$> lab
+
 regLink :: (Attr -> String -> String -> Inlines -> Inlines)
         -> F Inlines -> MarkdownParser (F Inlines)
 regLink constructor lab = try $ do

tests/markdown-reader-more.native

@@ -163,4 +163,6 @@ Pandoc (Meta {unMeta = fromList [("author",MetaList [MetaInlines [Str "Author",S
 ,Para [Link ("",[],[]) [Str "foo2"] ("","")]
 ,Header 2 ("wrapping-shouldnt-introduce-new-list-items",[],[]) [Str "Wrapping",Space,Str "shouldn\8217t",Space,Str "introduce",Space,Str "new",Space,Str "list",Space,Str "items"]
 ,BulletList
- [[Plain [Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "2015."]]]]
+ [[Plain [Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "blah",Space,Str "2015."]]]
+,Header 2 ("bracketed-spans",[],[]) [Str "Bracketed",Space,Str "spans"]
+,Para [Span ("id",["class"],[("key","val")]) [Emph [Str "foo"],Space,Str "bar",Space,Str "baz",Space,Link ("",[],[]) [Str "link"] ("url","")]]]

tests/markdown-reader-more.txt

@@ -287,3 +287,6 @@ bar
 
 - blah blah blah blah blah blah blah blah blah blah blah blah blah blah 2015.
 
+## Bracketed spans
+
+[*foo* bar baz [link](url)]{.class #id key=val}