Introduce different levels for the `optimization` build option

[filipesilva]

🚀 Feature request

Command (mark with an x)

- [ ] new
- [x] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Description

Introduce different levels for the optimization build option.

Describe the solution you'd like

We should have a way to disable unsafe optimizations, such as pure_getters.

Describe alternatives you've considered

Either having several levels (e.g. true > 'safe-only' > false) or having a per-option switch on a object.

Related issues:
#14187
#14287
#14316
#15607
#15751
#17255
#17494

[cloakedninjas]

Also related: #11439

[dgp1130]

Terser discussion of working around pure_getters: terser/terser#464

[laurentgoudet]

Originally posted by @alan-agius4 in #17517 (comment)

This was one of the changes in version 9 where server production code is minified, one of the main reasons behind this is to speed up server cold starts and reduce deployment times.
What I suggest is to generate sourcemaps and attach them, which will provide a better debug experience.

This is what I'm doing for Sentry, which works reasonably well (shipping the source maps to Sentry in CI), but I'm also shipping server-side logs to an ELK stack - with minified code those would show meaningless stack traces.

One way around could be to embed the source maps into the prod container & apply those on the error stack traces, but I'd rather not have that kind of logic running on errors, in order to ensure those are properly reported (and not swallowed), plus that'd defeat a bit the goal of reducing deployment times.

Not sure how others have solve these problems as the cold starts time & memory usage are indeed quite large (especially when running a 30+ locales app), but for the moment I'd still be interested by a proper way to turn off server-side code minification (a rollup pass or anything that does not make the code unreadable is fine though).