Question

.NET balanced group regexes make my head explode. I’ve got this string i’m trying to match:

other stuff blah blah....                     {                         stuff stuff                         {key:                             stuff                             stuff                         }                     } more stuff..... 

Here’s my regex:

[^{}]*                      # anything that isn't { } \{                          # starting with { (?>                         # atomic group: throw away backtracks on exit     [^{}]+   |     \{(?:\w+:)?(?<DEPTH>)   # on matching { plus optional 'word:' push stack     |     \}(?<-DEPTH>)           # on matching } pop stack )* (?(DEPTH)(?!))              # if depth unbalanced, fail match \}                          # ending with } [^{}]*                      # anything that isn't { } 

So, I’m trying to match balancing curly braces, where some of the opening curly braces have an optional word followed by a colon. The above regex matches my example string, but if i remove a curly brace, (i.e. ‘unbalancing it):

    other stuff blah blah....                     {                         stuff stuff                         {key:                             stuff                             stuff                      } more stuff..... 

…it still matches!

Can anyone tell me how to fix my regex?

Answer 1

Have you checked what it is matching in the second case? Since you don’t have any anchors, I think the engine starts the match just after the first ‘{‘. From there, until the end, the string matches.

Try surrounding the pattern with \A and \z.