JavaScript Minifier does not shorten variable/parameter names

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Issue

If you configure your Liferay instance like this:
```
minifier.enabled=true
javascript.fast.load=true
theme.images.fast.load=true
layout.template.cache.enabled=true
```
JavaScript Minifier removes blanks, line breaks, comments, etc. successfully, but it does not shorten variables or function parameter names.

For instance, if you have:

function foo(bar){
   alert(bar);
}

you get this output:

function foo(bar){alert(bar);}

instead of something like:

function foo(a){alert(a);}

It happens to both Liferay and custom development files.

Environment

DXP 7.1 or higher

Resolution

The minification is done by closure-compiler library at runtime.
Since the upgrade from version v20131014 to v20180204, the minifier has not worked as expected: it does not shorten variable/parameter names as described before.
- This has not been backported to 7.0.x yet, that's why DXP 7.0 is not affected.
- It is a known bug in closure-compiler library.
- Note that you may find fully minified files (usually YUI files) if they are served this way.
Solving the issue means performing a more aggressive minification. Trying to solve it now, after several years, has shown that unexpected errors appear at runtime.
- Note that the fast-load of the resources (serving multiple files in one resource) makes the platform more prone to these errors.
Furthermore, the presence of custom developed code could raise new errors there when trying more aggressive minification.
In Liferay DXP 7.4, this minification method (at runtime) has been deprecated in favor of a build-time minification (see LPS-122883).
Therefore, having all of the above into account, it has been decided that this issue will not be fixed.

Additional Information

See PTR-2671: closure-compiler library not minifying as expected for further details.