Add json5 support, closes #256

syntax/json5.vim

@@ -0,0 +1,56 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'json5') == -1
+  
+" Syntax setup {{{1
+if exists('b:current_syntax') && b:current_syntax == 'json5'
+  finish
+endif
+
+" Syntax: Strings {{{1
+syn region  json5String    start=+"+  skip=+\\\\\|\\"+  end=+"+  contains=json5Escape
+syn region  json5String    start=+'+  skip=+\\\\\|\\'+  end=+'+  contains=json5Escape
+
+" Syntax: Escape sequences
+syn match   json5Escape    "\\["\\/bfnrt]" contained
+syn match   json5Escape    "\\u\x\{4}" contained
+
+" Syntax: Numbers {{{1
+syn match   json5Number    "-\=\<\%(0\|[1-9]\d*\)\%(\.\d\+\)\=\%([eE][-+]\=\d\+\)\=\>"
+syn keyword json5Number    Infinity -Infinity
+
+" Syntax: An integer part of 0 followed by other digits is not allowed.
+syn match   json5NumError  "-\=\<0\d\.\d*\>"
+
+" Syntax: Boolean {{{1
+syn keyword json5Boolean   true false
+
+" Syntax: Null {{{1
+syn keyword json5Null      null
+
+" Syntax: Braces {{{1
+syn match   json5Braces	   "[{}\[\]]"
+syn match   json5ObjAssign /@\?\%(\I\|\$\)\%(\i\|\$\)*\s*\ze::\@!/
+
+" Syntax: Comment {{{1
+syn region  json5LineComment    start=+\/\/+ end=+$+ keepend
+syn region  json5LineComment    start=+^\s*\/\/+ skip=+\n\s*\/\/+ end=+$+ keepend fold
+syn region  json5Comment        start="/\*"  end="\*/" fold
+
+" Define the default highlighting. {{{1
+hi def link json5String             String
+hi def link json5ObjAssign          Identifier
+hi def link json5Escape             Special
+hi def link json5Number             Number
+hi def link json5Braces             Operator
+hi def link json5Null               Function
+hi def link json5Boolean            Boolean
+hi def link json5LineComment        Comment
+hi def link json5Comment            Comment
+hi def link json5NumError           Error
+
+if !exists('b:current_syntax')
+  let b:current_syntax = 'json5'
+endif
+
+" vim: fdm=marker
+
+endif