Preprocessing acts strange when used in combination with UglifyJsPlugin

[xaralis]

When used together with UglifyJsPlugin in production builds, this loader is very unreliable and unpredictable in HTML files.

Some things work (like echo, if), some things do not (like ifdef).

For example, this gets preprocessed OK:

<meta name="git-rev" content="<!-- @echo GIT_REV -->">

However, this fails:

<!-- @ifdef LAST_UPDATED -->
<d-updated-indicator when="<!-- @echo LAST_UPDATED -->"></d-updated-indicator>
<!-- @endif -->

Instead of producing nothing when LAST_UPDATED is undefined, it results in following code:

<d-updated-indicator when="undefined"></d-updated-indicator>

Can you please investigate and/or point me where to look for solution?

[dearrrfish]

Do you put preprocess before UglifyJS in build sequence?