mt3o/typedi-caveat

Typedi dependency injection caveat

It fails to Container.get() when class is imported, despite having in tsconfig.js:

    "compilerOptions":{
        "experimentalDecorators": true,
        "emitDecoratorMetadata": true,
        }

Enabling "importsNotUsedAsValues": "preserve" enables one of the test, it probably should be mentioned by typedi.

Experiment

Change importsNotUsedAsValues in tsconfig.json and redo tests. This toggles test (1) Change @Service({id:'baz'}) to @Service() and redo tests. This toggles test (2) and (3)

Final conclusions:

Contrary to Java, where DI works across whole project, with TS, all files must be explicitly imported somewhere in the project, and executed, before DI container notices them. So ts classes are like notice me sempai in nodejs world.

This behavior limits the capability of type-based injections, where many smaller objects interact on shared data like in the chain of responsibility pattern, as we can't dynamically inject all interface-matching objects and rely on autodetection. Classes are not autodetected, what's more, simply importing them doesn't work. Out of the box TS removes unused import calls, so at least "importsNotUsedAsValues": "preserve" is needed.