How to do multiline comment with conditional statements in ember.js script handlebars?

Question

I'm learning ember.js and would like to sometimes deactivate some chunks of code. I know {{! }} works for single-line commenting inside <script type="text/x-handlebars">, but I can't make it work for multi-line commenting. Maybe because I have conditional statements inside.

<script type="text/x-handlebars" id="stuff">     {{!       {{#if length}}         foobar       {{/if}}     }} </script> 

but then I got this error:

Uncaught Error: Parse error on line xx: ...ngth}}    foobar  {{/if}}}}    {{ o ---------------------^ Expecting 'EOF', got 'OPEN_ENDBLOCK'  

I also tried using <!-- ... -->, while the section is not shown, but I also get this error:

Uncaught Error: Cannot perform operations on a Metamorph that is not in the DOM

this error doesn't show up if I just delete that chunk of code.

Answer 1

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{{!--   This is a   multiline   comment --}} 

for multiline comments