Mismatched pragmas cause unpredictable output

[Jacques Favreau]

Issue

Currently, groundskeeper just matches on /^[<]([/]([^\s])[>]$/ for any pragma and then does an every-other pass to decide what to strip out without looking at the content of the directives. This means that a malformed directive can cause very unpredictable output. This initially came up when somebody removed the opening tag of a pragma, but forgot to remove the closing one.

Example

Source:

console.log('keep me!');
//<pragma>
console.log('remove me!');
// <oops>
console.log('remove me, too!');
// </pragma>
console.log('keep me!'); 

Output:

console.log('keep me!');
console.log('remove me, too!');

Proposal

Keep track of current open pragmas, and ignore mismatched directives.

[Jacques Favreau]

Having now worked with it, my proposal has shifted to throwing an error. It's much better to know you have broken code before you get it up on your server ;)

[Luís Couto]

Don't get me wrong but this project has been deprecated since UglifyJS (and now terser) support their own flavor of pragmas: https://github.com/mishoo/UglifyJS2#conditional-compilation