CODEWITHSUNDEEP
typescriptgenericsjsdoc
thijsfranck
thijsfranck

Reputation: 808

Inherit JSDoc from generic parameter in TypeScript

I have written a wrapper function memoize that caches the results of a function by its arguments. I would like the type hint for the wrapped function to show the original docs.

Here is what the type hint currently shows:

Current type hint

And here is how I have declared my Memoized type:

/**
 * Functions that match this type can be memoized.
 */
type Memoizable = (...args: any[]) => any;

/**
 * The memoized function.
 */
interface Memoized<T extends Memoizable> {
    /**
     * Memoized function that caches its results by a key built from its arguments.
     */
    (...args: Parameters<T>): ReturnType<T>;
    /**
     * The cache from which memoized items are retrieved.
     */
    readonly cache: Map<string, ReturnType<T>>;
}

So instead if the documentation for Memoized, I want to show the documentation for my function test. My guess is that I need to declare Memoized differently. What am I missing?

View the full example on TS Playground

Upvotes: 0

Views: 827

Answers (1)

thijsfranck
thijsfranck

Reputation: 808

Turns out the solution was to declare Memoized as follows:

/**
 * Memoized function that exposes its cache.
 */
type Memoized<T extends Memoizable> = T & Memo<T>

/**
 * A memoized function exposes its cache as a read-only attribute.
 */
interface Memo<T extends Memoizable> {
    /**
     * The cache from which memoized items are retrieved.
     */
    readonly cache: Map<string, ReturnType<T>>;
}

Now the type hint looks like this:

Correct type hint

View the full example on TS Playground

Upvotes: 1

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