Add option to use Parens Decorators

Parens decorators are symbols that can be used inside parens and create
a custom compound open-close sequence.
It is useful for some templating languages such as [Jinja](http://jinja.pocoo.org/)/[Twig](twig.sensiolabs.org)/[Liquid](https://github.com/Shopify/liquid)
and must be opted in with a config option.

Closes jiangmiao#144

README.md

@@ -40,6 +40,14 @@ Features
         input: '|' (press <SPACE> at |)
         output: ' |'
 
+*   Insert Parens decorators for [], (), {}. Useful for templating languages such as [Jinja](http://jinja.pocoo.org/)/[Twig](twig.sensiolabs.org)/[Liquid](https://github.com/Shopify/liquid)
+
+        input: {|} (press % at |)
+        output {%|%}
+
+        input: {|} (press #<SPACE>foo at |)
+        output {# foo| #}
+
 *   Skip ' when inside a word
 
         input: foo| (press ' at |)
@@ -183,6 +191,30 @@ Options
 
         Buffer level pairs set.
 
+*   g:AutoPairsEnableParensDecorators
+
+        Default: 0
+
+        Enables parens decorators, such as %, #, =.
+
+*   g:AutoPairsParens
+
+        Default: {'(':')', '[':']', '{':'}'}
+
+        Which pairs should be considered paren.
+
+*   g:AutoPairsParensDecorators
+
+        Default: {'%':'%', '#':'#', '=':'='}
+
+        Parens decorator value pairs.
+
+*   b:AutoPairsParensDecorators
+
+        Default: g:AutoPairsParensDecorators
+
+        Buffer level parens decorator set.
+
 *   g:AutoPairsShortcutToggle
 
         Default: '<M-p>'

plugin/auto-pairs.vim

@@ -20,6 +20,14 @@ if !exists('g:AutoPairsParens')
   let g:AutoPairsParens = {'(':')', '[':']', '{':'}'}
 end
 
+if !exists('g:AutoPairsEnableParensDecorators')
+  let g:AutoPairsEnableParensDecorators = 0
+end
+
+if !exists('g:AutoPairsParensDecorators')
+  let g:AutoPairsParensDecorators = {'%':'%', '#':'#', '=':'='}
+end
+
 if !exists('g:AutoPairsMapBS')
   let g:AutoPairsMapBS = 1
 end
@@ -245,15 +253,19 @@ function! AutoPairsDelete()
   endif
 
   " Delete Repeated Pair eg: '''|''' [[|]] {{|}}
-  if has_key(b:AutoPairs, prev_char)
+  if (has_key(b:AutoPairs, prev_char) || has_key(b:AutoPairsParensDecorators, prev_char))
     let times = 0
     let p = -1
     while get(prev_chars, p, '') == prev_char
       let p = p - 1
       let times = times + 1
     endwhile
 
-    let close = b:AutoPairs[prev_char]
+    if has_key(b:AutoPairs, prev_char)
+      let close = b:AutoPairs[prev_char]
+    else
+      let close = b:AutoPairsParensDecorators[prev_char]
+    endif
     let left = repeat(prev_char, times)
     let right = repeat(close, times)
 
@@ -413,15 +425,20 @@ function! AutoPairsReturn()
   return ''
 endfunction
 
-function! AutoPairsSpace()
+function! AutoPairsDecorator(decorator, closing)
   let line = getline('.')
   let prev_char = line[col('.')-2]
   let cmd = ''
-  let cur_char =line[col('.')-1]
-  if has_key(g:AutoPairsParens, prev_char) && g:AutoPairsParens[prev_char] == cur_char
-    let cmd = "\<SPACE>".s:Left
+  let cur_char = line[col('.')-1]
+  if ((has_key(g:AutoPairsParens, prev_char) && g:AutoPairsParens[prev_char] == cur_char)
+        \|| (has_key(b:AutoPairsParensDecorators, prev_char) && b:AutoPairsParensDecorators[prev_char] == cur_char))
+    let cmd = a:closing.s:Left
   endif
-  return "\<SPACE>".cmd
+  return a:decorator.cmd
+endfunction
+
+function! AutoPairsSpace()
+  return AutoPairsDecorator("\<SPACE>", "\<SPACE>")
 endfunction
 
 function! AutoPairsBackInsert()
@@ -445,6 +462,10 @@ function! AutoPairsInit()
     let b:AutoPairs = g:AutoPairs
   end
 
+  if !exists('b:AutoPairsParensDecorators')
+    let b:AutoPairsParensDecorators = g:AutoPairsParensDecorators
+  end
+
   if !exists('b:AutoPairsMoveCharacter')
     let b:AutoPairsMoveCharacter = g:AutoPairsMoveCharacter
   end
@@ -482,6 +503,13 @@ function! AutoPairsInit()
     execute 'inoremap <buffer> <silent> <SPACE> '.do_abbrev.'<C-R>=AutoPairsSpace()<CR>'
   end
 
+  if g:AutoPairsEnableParensDecorators
+    let decorators = items(b:AutoPairsParensDecorators)
+    for decorator in decorators
+      execute 'inoremap <buffer> <silent> '.decorator[0]." <C-R>=AutoPairsDecorator('".decorator[0]."', '".decorator[1]."')<CR>"
+    endfor
+  end
+
   if g:AutoPairsShortcutFastWrap != ''
     execute 'inoremap <buffer> <silent> '.g:AutoPairsShortcutFastWrap.' <C-R>=AutoPairsFastWrap()<CR>'
   end