[Suggestion] Allow to set terser mangle options

[jantimon]

Current Behaviour

Right now TSDX provides good defaults for terser / uglify-es.
Unfortunately fine tuning prop mangling is not supported right now.

Desired Behaviour

As a library author file size is important for me.
Using prop mangling on a project saved ~10% in size (after gzip).

For example given the following code:

const state = { count: 0 };
state.count ++;

Minifying it with terser/uglify-es reduces the following outputs

1. without mangling
2. with mangling

var s={count:0};s.count++;

var s={c:0}s.c++;

This would allows me adding more features for the same file size.

As you can probably guess this will only work for internal library code as mangling public option names would not be a good idea:
E.g. Mangling if(options.verbose){..} to if(o.verbose){..} will still work however if(o.x){..} won't.

Therefore terser/uglify-es allows to limit propMangling using a regular expression.
So as a library author I can tell terser to mangle only props starting with a _:

const state = { _count: 0 };
if (options.verbose) { console.log(state._count) }

with a regular expression /^_/ would produce the following:

var s={c:0};if(o.verbose){console.log(s.c)}

Try it out yourself: runkit live demo

Suggested Solution

Allow to set a regex for props mangling - if none is given don't mangle props at all.

Who does this impact? Who is this for?

This helps library authors to provide smaller libraries.

Describe alternatives you've considered

For example codekit uses a prop whitelist instead of a regular expression: https://codekitapp.com/help/terser/

Additional context

runkit live demo
terser docs

[swyxio]

great writeup. we'll probably enable this through a general "extend your own rollup config" option #110

[agilgur5]

This should be possible now by extending the Rollup config in tsdx.config.js that was added in #183 .

If that is too difficult or if this is a more common request we can think about more easily configuring it. I believe microbundle has a flag for this, but we want to avoid flag sprawl if possible through other means (and IMO config is better than flags generally)