I can not undo the snippet expansion

[yfzhao20]

Related to issue 27. I can not undo that!

snippet ( "()" iA
($1)$0
endsnippet

snippet `(?<=[a-zA-z])([0-9])` "d" iA
_``rv=m[1]``
endsnippet

[draivin]

Thanks for the report, the issue on both those examples is that the undo action is inserting exactly 1 character, and there is no way that I know of to tell the difference between an undo action and a user keypress. For instance, in your first example, if you selected the text () and typed (, the edit event we receive would be exactly the same as the event we receive from the undo action.

I'll try to think of a solution for this, but nothing is coming to mind right now.

[draivin]

As a sidenote, in the second example you can fix this by actually matching the letters and numbers, instead of using a lookbehind, so it would look something like:

snippet `([a-zA-z])([0-9])` "d" iA
``rv=m[1]``_``rv=m[2]``
endsnippet