Decide: `@Injectable` imported under an alias — ngtsc emits no `ɵfac`, OXC does

[Brooooooklyn]

With #504, OXC finds Angular class decorators by their @angular/core import, so an aliased @Injectable is now compiled. ngtsc 22.1.7 compiles it differently. It looks like an ngtsc bug. This issue records the difference and asks whether we keep OXC's output.

Repro

import {Injectable as X} from '@angular/core';
@X({providedIn: 'root'})
export class S {}

ngtsc 22.1.7

export class S {
    static ɵprov = /*@__PURE__*/ i0.ɵɵdefineInjectable({ token: S, factory: S.ɵfac, providedIn: 'root' });
}

static ɵprov: i0.ɵɵInjectableDeclaration<any>;

No ɵfac and no setClassMetadata. ɵprov.factory points at S.ɵfac, which doesn't exist, so injecting S fails at runtime.

Cause, in packages/compiler-cli/src/ngtsc/annotations/src/injectable.ts:

needsFactory:
  meta.decorators === null ||
  decorators.every((current) => !isAngularCore(current) || current.name === 'Injectable'),

current.name is the name as written (X), so an aliased import gives needsFactory = false. setClassMetadata is only emitted inside if (analysis.needsFactory), so it is dropped too.

OXC (#504 tip)

export class S {
static ɵfac = /*@__PURE__*/ (() =>{
  let ɵS_BaseFactory;
  return function S_Factory(__ngFactoryType__) {
    return (ɵS_BaseFactory || (ɵS_BaseFactory = i0.ɵɵgetInheritedFactory(S)))((__ngFactoryType__ || S));
  };
})();
static ɵprov = /*@__PURE__*/ i0.ɵɵdefineInjectable({token:S,factory:S.ɵfac,providedIn:"root"});
}
// + ɵsetClassMetadata(S,[{type:X,args:[{providedIn:"root"}]}],null,null)

static ɵfac: i0.ɵɵFactoryDeclaration<S, never>;
static ɵprov: i0.ɵɵInjectableDeclaration<S>;

On main the aliased decorator is not recognized at all, so the class is left as written (@X({providedIn: 'root'}) export class S {}).

Decision needed

• Keep OXC's output (a working factory). This is a known difference from ngtsc. Add it to napi/angular-compiler/e2e/compare/fixtures/known-differences.ts.
• Or copy ngtsc's output exactly. That gives a broken ɵprov.

Recommendation: keep it, record the difference, and maybe report it upstream.

Note: the ɵgetInheritedFactory form and InjectableDeclaration<S> vs <any> also show up for a plain @Injectable() class with no constructor, on main too. Not specific to the alias.