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Angular 19 forRoot() gets called twice in developer build (v18 only once) #60905
Closed as not planned
Description
Which @angular/* package(s) are the source of the bug?
core
Is this a regression?
Yes
Description
I provide two ng new --standalone=false projects, one in Angular 19 and the other Angular 18.
In the develop build in Angular 19 forRoot will be called twice while in Angular 18 it will be called only once (see console.log output).
For production build both only call forRoot() once.
There is a console.log() in the forRoot() of the TestModule.
Is it a known consequence of the migration from angular 18 to 19 ?
See example code in the attachment.
in v19 forRoot Called will be console logged twice while in v18 it will be once in development build
class TestModule {
static forRoot(): ModuleWithProviders<TestModule> {
console.log('forRoot Called');
return {
ngModule: TestModule,
};
}
}
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
TestModule.forRoot()
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
Please provide a link to a minimal reproduction of the bug
See attachment
Activity
[-]Angular 19 forRoot() gets called twice[/-][+]Angular 19 forRoot() gets called twice in developer build (v18 only once)[/+]JeanMeche commentedon Apr 17, 2025
Interesting, something changed in 19.2.7.
19.2.6 and previous version do not exhibit this.
Edit: This is due to #30021.
JoostK commentedon Apr 18, 2025
This behavior itself is tracked in #38376. It started to become relevant for AOT apps again due to angular/angular-cli#30021.
teoeter commentedon Apr 18, 2025
This change might not be suited for a patch.
It could cause some headaches and debugging for library authors who use it for initialization.
We have a warning in the demo app for the library that appears if forRoot is accidentally initialized twice (a potential regression due to misconfiguration); that's how we detected it.
The reason is that there might be some logic in a library that should only be done once.
This can easily be controlled using an already initialized state if Angular doesn't guarantee that it's only done once, and we want the same behavior in development and production.
If Angular decides to proceed with this, that's fine, but maybe it shouldn't be in a patch release and should be announced in the migration notes.
JoostK commentedon Apr 18, 2025
It wasn't a known side-effect of angular/angular-cli#30021 and that issue is fixing a limitation that used to be present for AOT compiled apps in tests, hence it was included in a patch release. Angular's
ModuleWithProvidersfunctions are expected to be side-effect free.How is this done, exactly? I assume this is achieved using some global state that is used as side-channel to detect multiple calls?
alxhub commentedon Apr 18, 2025
Closing as a duplicate of #38376, which is now closed as well. In general, this is working as intended. In general,
ModuleWithProvidersfunctions shouldn't have side effects. Angular hasprovideAppInitializerandprovideEnvironmentInitializerfor adding initialization logic, which is where such validation should take place. A common pattern I've seen is to provide a multiprovider token inforRoot, and use an initializer to check the number of values received for that token. If there's more than one, thenforRootwas included too many times.angular-automatic-lock-bot commentedon May 19, 2025
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