Some unsupported code with es2015 target set

[SetoKaiba]

Which @angular/* package(s) are the source of the bug?

common

Is this a regression?

No

Description

This is not supported for es2015. But it's still there after compile. I'm trying to write a webpage for OBS studio. The ?. is not supported I think. And I think it's not in es2015 as well.

Here is the tsconfig. Set target to es2015 doesn't help. But the unsupported is gone if I set target to es5.
https://github.com/angular/angular/blob/b5ab7aff433a67cddaa55e621d17b1a1b07b57c2/packages/common/src/location/location_strategy.ts#L176-L178
Why this ?. is kept even I set target to es2015?

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

No response

Please provide the environment you discovered this bug in (run ng version)

No response

Anything else?

No response

[JoostK]

The occurrence of ?. exists in library code, which has already been compiled to JS. Therefore, the target option of your TypeScript compilation is irrelevant.

I'm afraid that without more insight into your building process, we'd be unable to help you. Please share a reproduction.

[SetoKaiba]

@JoostK Just create an empty project with angular cli 13.0.3. Change the tsconfig.json target to es2015. ng serve. You will see the problematic code in vendor.js:8571.

[JoostK]

What version of Chrome are you using?

[SetoKaiba]

@JoostK If I change the target to es5, the problem gone. If it's a compiled library code, why?

I'm using the OBS studio with browser source. So I don't know what's the version of chrome it used.

And this is the remote debug for OBS studio browser. That's why I can find out the ?. is not supported.

I supposed ?. is a feature introduced in es10(2019).

[SetoKaiba]

If I change the target to es5, the problem gone.

[JoostK]

The optional chaining support landed in Chrome 80, quite a while ago. Angular only supports the latest major of Chrome; if OBS is using an outdated version then Angular apps may break in unexpected ways.

The CLI has some heuristics to determine the output format to generate. It looks like it treats es5 targets differently than es2015. @alan-agius4 probably knows more about this, the output format of libraries might also depend on the browserslist configuration.

[alan-agius4]

In case the target is ES2019 or lower we should favour the FESM2015 entry-point.