正则表达式匹配未转义的大括号

Question

I'm currently trying to make a regex to match the closest pair of an opening and closing bracket without matching escaped braces. (And without matching double escape characters infront of a non escaped bracket).

{"asd"} - {"asd"}
\{"test"} - No match
\\{"Apple juice}"} - {"Apple juice}"}
{{"Test"}} - {"Test"}

I'd already be glad to find a regex which just maches unescaped characters without using \\K I have tried multiple things but I can't figure out why this regex doesn't work: ((?<!\\\\)(?=(?:\\\\{2})*)){

Answer 1

You can use

(?<!\\)\\[{}]|(\{(?:"[^"\\]*(?:\\.[^"\\]*)*"|[^{}]*)(?:\\.(?:"[^"\\]*(?:\\.[^"\\]*)*"|[^{}]*))*})

See regex demo

The regex matches 2 alternatives:

• (?<!\\\\)\\\\[{}] - an escaped opening or closing brace with no \\ in front

OR (this one is captured, so you can grab it by accessing the first capturing group)

• (\\{(?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"|[^{}]*)(?:\\\\.(?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*‌​"|[^{}]*))*}) - matches and captures into Group 1 a substring starting with
  • \\{ - opening brace
  • (?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"|[^{}]*) - a quoted string containing any escaped sequences ( "[^"\\\\]*(?:\\\\.[^"\\\\]*)*") or 0 or more characters other than { and } ( [^{}]* )
  • (?:\\\\.(?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*‌​"|[^{}]*))* - matches 0 or more sequences of...
    • \\\\. - escaped sequence
    • (?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*‌​"|[^{}]*) - see description above
• } - closing brace