Maintenance: test repo & packages with TypeScript 5.x

[dreamorosi]

Summary

On March 16th TypeScript 5.0 was released. Among other things, the release has some changes related to decorators support.

We should invest some time to test the project with the new version, understand if there's any implication, and if any change is required.

Why is this needed?

We can expect customers will want to start using the new TS version and so we need to test compatibility.

Which area does this relate to?

Other

Solution

No response

Acknowledgment

• This request meets Lambda Powertools Tenets
• Should this be considered in other Lambda Powertools languages? i.e. Python, Java, and .NET

Future readers

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[dreamorosi]

After some initial research, it appears that the signature/type of how decorators are defined in TS has changed with the new version. This is unfortunate but also not surprising since decorators as a feature in TypeScript/JavaScript are still experimental.

Prior to TS5.0, the signature was this:

type MethodDecorator = <T>(
  target: Object,
  propertyKey: string | symbol,
  descriptor: TypedPropertyDescriptor<T>
) => TypedPropertyDescriptor<T> | void;

Now, with TS5.0, the signature looks like this:

type ClassMethodDecorator = (
  value: Function,
  context: {
    kind: "method";
    name: string | symbol;
    access: { get(): unknown };
    static: boolean;
    private: boolean;
    addInitializer(initializer: () => void): void;
  }
) => Function | void;

Source

The main differences that I can see will affect us are:

• The decorated method is now value (first argument) instead of descriptor.value (3rd argument, which we use now)
• Number of arguments goes from 3 to 2
• The name of the decorated method/function is now context.name and not propertyKey (which has now been removed)

The next step should be to create a small PoC to validate the findings above.