In my Angular app, I'm trying to use a factory provider in my module:
export function getMyFactory(): () => Window { return () => window; } @NgModule({ providers: [ { provide: WindowRef, useFactory: getMyFactory() }, ], }) export class MyModule {} but this is failing with:
Error encountered in metadata generated for exported symbol 'MyModule':
Metadata collected contains an error that will be reported at runtime: Lambda not supported
I've found an easy solution reported on a thread from GitHub: Arrow lambda not supported in static function posted by haochi
The solution is basically:
assigning the result to a variable, then return the variable
So in my case, I've resolved by replacing:
export function getMyFactory(): () => Window { return () => window; } with:
export function getMyFactory(): () => Window { const res = () => window; return res; } 
Just add the // @dynamic comment like this:
// @dynamic export function getMyFactory(): () => Window {return () => window;} More info in the angular docs
This same error happened to me in an Angular library.
I ignored it by setting "strictMetadataEmit": false, in tsconfig.lib.json under angularCompilerOptions.
I had the same issue trying to return a promise as a function, and replaced this:
export function myFunc(): Function { const result = () => ... return result; } With:
export function myFunc(){ const result = () => ... return result; } 