bug: prevent "' from being a valid region (which is not)

syntax/vue.vim

@@ -76,11 +76,19 @@ syn match   htmlArg "[@#v:a-z][-:.0-9_a-z]*\>" contained
 " Prevent 0 lenght vue dynamic attributes from (:id="") from overflowing from
 " the area described by two quotes ("" or '') this works because syntax
 " defined earlier in the file have priority.
-syn match htmlString /\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<=["']\{2\}/ containedin=ALLBUT,htmlComment
+syn match htmlString /\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<=""/ containedin=ALLBUT,htmlComment
+syn match htmlString /\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<=''/ containedin=ALLBUT,htmlComment
 
 " Actually provide the JavaScript syntax highlighting.
-syn region vueJavascriptInTemplate start=/\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<=["']/ms=e+1 keepend end=/["']/me=s-1 contains=@jsAll containedin=ALL
+
+" for mustaches quotes (`{{` and `}}`)
 syn region vueJavascriptInTemplate matchgroup=htmlSpecialChar start=/{{/ keepend end=/}}/ contains=@jsAll containedin=ALLBUT,htmlComment
+" for double quotes (") and for single quotes (')
+syn region vueJavascriptInTemplate start=/\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<="/ms=e+1 keepend end=/"/me=s-1 contains=@jsAll containedin=ALL
+syn region vueJavascriptInTemplate start=/\(\([@#:]\|v-\)[-:.0-9_a-z]*=\)\@<='/ms=e+1 keepend end=/'/me=s-1 contains=@jsAll containedin=ALL
+" It's necessary to have both because we can't start a region with double
+" quotes and it with a single quote, and removing `keepend` would result in
+" side effects.
 
 syntax sync fromstart