Attribute in parentheses such as div[(test)] doesn't expand properly

[rzhao271]

Test case

equal(expand('div[(hello)]'), '<div (hello)=""></div>');

Output

1) Expand Abbreviation
npm ERR!        Markup
npm ERR!          attributes:
npm ERR!
npm ERR!       AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:
npm ERR! + actual - expected
npm ERR!
npm ERR! + '<div (hello}=""></div>'
npm ERR! - '<div (hello)=""></div>'
npm ERR!               ^
npm ERR!       + expected - actual
npm ERR! 
npm ERR!       -<div (hello}=""></div>
npm ERR!       +<div (hello)=""></div>
npm ERR!

Expected behaviour

Tests pass and the (hello) part stays the same in the expanded abbreviation.

Actual behaviour

The closing parenthesis ) becomes a closing brace }. Trying to expand div[(hello\)] results in the same issue.