Avoid using unnecessary generic types while updating a TypeScript interface on DefinitelyTyped, especially when using DTSLint

Question

Avoid using unnecessary generic types while updating a TypeScript interface on DefinitelyTyped, especially when using DTSLint

After attempting to utilize a specific library (query-string), I realized that the 'parse' function was returning an any type. To address this, I decided to update the type definitions to include a generic.

As a result, I forked the DefinitelyTyped repository and made changes to the definition:

export function parse(str: string, options?: ParseOptions): any;

which I modified to:

export function parse<T>(str: string, options?: ParseOptions): T;

However, upon attempting to compile, I received the following error message:

https://github.com/Microsoft/dtslint/blob/master/docs/no-unnecessary-generics.md

I am struggling to understand why this would pose a problem. Do I need to cast it in my personal project?

typescript tslint

Answer 1

Answer №1

In this scenario, the generic parameter serves no purpose as it does not contribute to the function's inner logic. The same type coercion can be achieved using an external option. A generic parameter should only be used if it is essential to the function or class signature.

// Not recommended. The generic can be eliminated
function parse<T>(): T;
const x = parse<number>();

// Better approach. No unnecessary generics
function parse(): {};
const x = parse() as number;

// Best practice. The generic must remain
function identity<T>(arg: T): T {
    return arg;
}

Answer 2

In this scenario, the generic parameter serves no purpose as it does not contribute to the function's inner logic. The same type coercion can be achieved using an external option. A generic parameter should only be used if it is essential to the function or class signature.

// Not recommended. The generic can be eliminated
function parse<T>(): T;
const x = parse<number>();

// Better approach. No unnecessary generics
function parse(): {};
const x = parse() as number;

// Best practice. The generic must remain
function identity<T>(arg: T): T {
    return arg;
}

Avoid using unnecessary generic types while updating a TypeScript interface on DefinitelyTyped, especially when using DTSLint

Answer №1

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