79 lines
3.0 KiB
Markdown
79 lines
3.0 KiB
Markdown
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# `ModuleWithProviders` Migration
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## What does this schematic do?
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Some Angular libraries, such as `@angular/router` and `@ngrx/store`, implement APIs that return a type called `ModuleWithProviders` (typically via a method named `forRoot()`).
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This type represents an `NgModule` along with additional providers.
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Angular version 9 deprecates use of `ModuleWithProviders` without an explicitly generic type, where the generic type refers to the type of the `NgModule`.
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This schematic will add a generic type to any `ModuleWithProviders` usages that are missing the generic.
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In the example below, the type of the `NgModule` is `SomeModule`, so the schematic changes the type to be `ModuleWithProviders<SomeModule>`.
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**Before**
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```ts
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@NgModule({...})
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export class MyModule {
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static forRoot(config: SomeConfig): ModuleWithProviders {
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return {
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ngModule: SomeModule,
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providers: [
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{provide: SomeConfig, useValue: config}
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]
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};
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}
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}
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```
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**After**
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```ts
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@NgModule({...})
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export class MyModule {
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static forRoot(config: SomeConfig): ModuleWithProviders<SomeModule> {
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return {
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ngModule: SomeModule,
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providers: [
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{provide: SomeConfig, useValue: config }
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]
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};
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}
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}
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```
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In the rare case that the schematic can't determine the type of `ModuleWithProviders`, you may see the schematic print a TODO comment to update the code manually.
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## Why is this migration necessary?
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`ModuleWithProviders` has had the generic type since Angular version 7, but it has been optional.
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This has compiled because the `metadata.json` files contained all the metadata.
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With Ivy, `metadata.json` files are no longer required, so the framework cannot assume that one with the necessary types has been provided.
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Instead, Ivy relies on the generic type for `ModuleWithProviders` to get the correct type information.
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For this reason, Angular version 9 deprecates `ModuleWithProviders` without a generic type.
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A future version of Angular will remove the default generic type, making an explicit type required.
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## Should I add the generic type when I add new `ModuleWithProviders` types to my application?
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Yes, any time your code references the `ModuleWithProviders` type, it should have a generic type that matches the actual `NgModule` that is returned (for example, `ModuleWithProviders<MyModule>`).
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## What should I do if the schematic prints a TODO comment?
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The schematic will print a TODO comment in the event that it cannot detect the correct generic for the `ModuleWithProviders` type.
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In this case, you'll want to manually add the correct generic to `ModuleWithProviders`. It should match the type of whichever `NgModule` is returned in the `ModuleWithProviders` object.
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## What does this mean for libraries?
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Libraries should add the generic type to any usages of the `ModuleWithProviders` type.
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## What about applications using non-migrated libraries?
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`ngcc` should transform any non-migrated libraries to generate the proper code.
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For more information on `ngcc` see the [ngcc guide](guide/ngcc).
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