Provide an ability to perform tree-shaking but retain symbol names

[AndrewKushnir]

🚀 Feature request

Command (mark with an x)

• build

Description

Currently it's not possible to use ng build to perform dead code elimination via Terser, but retain symbol names in generated JS bundle. It'd be useful to have this capability to simplify bundle size-related investigations (which often times involves looking for retained symbols).

// cc @alan-agius4

[alan-agius4]

What myself and @AndrewKushnir observed was that using NG_BUILD_MANGLE=0 caused a lot of dead code such as DebugNode to be retained.

ng config cli.cache.enabled false
NG_BUILD_MANGLE=0 ng build

[johncrim]

I use this to test non-mangled production output:

cross-env NG_BUILD_DEBUG_OPTIMIZE=minify,beautify ng build --configuration production --output-hashing none

As I recall I arrived at that by reviewing the code that handles the different flags.

Does that suffer from the same problem?

[alan-agius4]

@johncrim, yeah since in that case mangled is disabled. At least in v13, you can verify this by looking for DebugNode, if it’s found DCE didn’t fully work.