Debug: make a function helper with stack trace

[qfox]

Something like: new Error().stack for usual JS but for bem-xjst templates.

Stack should contains only user templates and external calls and skip internal bem-xjst code.
Helper should be possible to call from any user template.

Something like:

bemhtml.compile(function(){
  block('b').def()(function(){ console.log(this.trace()); });
});
bemhtml.apply({block: 'b'});
// Trace
//     at b.def:1:13 (b.bemhtml.js:1:42)
//     at repl:4:1

cc @a-x-

[miripiruni]

@zxqfox BTW you can not use this.trace() with () => console.log(this.trace()) as template body. You need use regular function, not arrow function.

;)

[qfox]

@miripiruni fixed, ty.

[miripiruni]

The question is: «show me trace route how templates work».