Add mdx support, closes #342

after/syntax/mdx.vim

@@ -0,0 +1,45 @@
+if exists('g:polyglot_disabled') && index(g:polyglot_disabled, 'mdx') != -1
+  finish
+endif
+
+
+" based on mxw/vim-jsx
+
+if exists('b:current_syntax')
+  let s:current_syntax=b:current_syntax
+  unlet b:current_syntax
+endif
+syn include @XMLSyntax syntax/xml.vim
+if exists('s:current_syntax')
+  let b:current_syntax=s:current_syntax
+endif
+
+" JSX attributes should color as JS.  Note the trivial end pattern; we let
+" jsBlock take care of ending the region.
+syn region xmlString contained start=+{+ end=++ contains=jsBlock,javascriptBlock
+
+" JSX child blocks behave just like JSX attributes, except that (a) they are
+" syntactically distinct, and (b) they need the syn-extend argument, or else
+" nested XML end-tag patterns may end the outer jsxRegion.
+syn region jsxChild contained start=+{+ end=++ contains=jsBlock,javascriptBlock
+  \ extend
+
+" Highlight JSX regions as XML; recursively match.
+"
+" Note that we prohibit JSX tags from having a < or word character immediately
+" preceding it, to avoid conflicts with, respectively, the left shift operator
+" and generic Flow type annotations (http://flowtype.org/).
+syn region jsxRegion
+  \ contains=@Spell,@XMLSyntax,jsxRegion,jsxChild,jsBlock,javascriptBlock
+  \ start=+\%(<\|\w\)\@<!<\z([a-zA-Z][a-zA-Z0-9:\-.]*\)+
+  \ skip=+<!--\_.\{-}-->+
+  \ end=+</\z1\_\s\{-}>+
+  \ end=+/>+
+  \ keepend
+  \ extend
+
+" Add jsxRegion to the lowest-level JS syntax cluster.
+syn cluster jsExpression add=jsxRegion
+
+" Allow jsxRegion to contain reserved words.
+syn cluster javascriptNoReserved add=jsxRegion