get method type to boolean is resolved to unknown

[C0ZEN]

Hello,

Since the migration from Angular 8 to 9,
I have a type problem here with storageMap.get().

When using a generic type as boolean, the overload should be:

get<T = boolean>(key: string, schema: JSONSchemaBoolean): Observable<boolean | undefined>;

But in reality, the result is:

get<T = unknown>(key: string, schema?: JSONSchema): Observable<unknown>;

You can checkout the problem on StackBlitz on the app.component.ts.

[cyrilletuzi]

Hello, thanks for the precise issue and the stackblitz reproduction.

This is working as intended.

You're getting a value from client-side storage. So assuming you'll get what you previously stored is not safe: it could have been forged. So it's why the lib is returning unknown if you don't provide a JSON schema for runtime validation (validation can't be done at compilation time via a cast). You can see in the overload you provided that the second param is required.

So what you need to do is this:

this.storage.get('hello', { type: 'boolean' });

But this is not a change in v9 of this lib. It was a change in v7. So maybe something during Angular v8 to v9 migration made you aware of this, but this is not new.

More information about:

• background of the change from any to unknown in v7
• why validation is done via JSON schema and not via a cast, and how to validate properly since v8+

[C0ZEN]

Thank you for the information.

And yes, Angular 9 uses now a more recent version of TypeScript.
I guess than the type system checker is less permissive.