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[@types/lodash] Infer lodash.throttle return type from 'leading' option #69504

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merged 3 commits into from
May 16, 2024
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[@types/lodash] Infer lodash.throttle return type from 'leading' option #69504

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c7c189e
infer lodash.throttle return type from 'leading' option
dawaltconley May 3, 2024
b00febf
fix throttle overloads to handle boolean variables and explicit undef…
dawaltconley May 3, 2024
4c69ba6
clean up tests
dawaltconley May 13, 2024
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10 changes: 10 additions & 0 deletions types/lodash/common/function.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1355,6 +1355,7 @@ declare module "../index" {
*/
trailing?: boolean | undefined;
}
type ThrottleSettingsLeading = (ThrottleSettings & { leading: true }) | Omit<ThrottleSettings, 'leading'>
interface LoDashStatic {
/**
* Creates a throttled function that only invokes func at most once per every wait milliseconds. The throttled
Expand All @@ -1372,12 +1373,17 @@ declare module "../index" {
* @param options.trailing Specify invoking on the trailing edge of the timeout.
* @return Returns the new throttled function.
*/
throttle<T extends (...args: any) => any>(func: T, wait?: number, options?: ThrottleSettingsLeading): DebouncedFuncLeading<T>;
throttle<T extends (...args: any) => any>(func: T, wait?: number, options?: ThrottleSettings): DebouncedFunc<T>;
}
interface Function<T extends (...args: any) => any> {
/**
* @see _.throttle
*/
throttle(
wait?: number,
options?: ThrottleSettingsLeading
): T extends (...args: any[]) => any ? Function<DebouncedFuncLeading<T>> : never;
throttle(
wait?: number,
options?: ThrottleSettings
Expand All @@ -1387,6 +1393,10 @@ declare module "../index" {
/**
* @see _.throttle
*/
throttle(
wait?: number,
options?: ThrottleSettingsLeading
): T extends (...args: any[]) => any ? FunctionChain<DebouncedFuncLeading<T>> : never;
throttle(
wait?: number,
options?: ThrottleSettings
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6 changes: 3 additions & 3 deletions types/lodash/fp.d.ts
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Expand Up @@ -4173,10 +4173,10 @@ declare namespace _ {
interface LodashThrottle {
(wait: number): LodashThrottle1x1;
<T extends (...args: any) => any>(wait: lodash.__, func: T): LodashThrottle1x2<T>;
<T extends (...args: any) => any>(wait: number, func: T): lodash.DebouncedFunc<T>;
<T extends (...args: any) => any>(wait: number, func: T): lodash.DebouncedFuncLeading<T>;
}
type LodashThrottle1x1 = <T extends (...args: any) => any>(func: T) => lodash.DebouncedFunc<T>;
type LodashThrottle1x2<T extends (...args: any) => any> = (wait: number) => lodash.DebouncedFunc<T>;
type LodashThrottle1x1 = <T extends (...args: any) => any>(func: T) => lodash.DebouncedFuncLeading<T>;
type LodashThrottle1x2<T extends (...args: any) => any> = (wait: number) => lodash.DebouncedFuncLeading<T>;
interface LodashThru {
<T, TResult>(interceptor: (value: T) => TResult): LodashThru1x1<T, TResult>;
<T>(interceptor: lodash.__, value: T): LodashThru1x2<T>;
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57 changes: 44 additions & 13 deletions types/lodash/lodash-tests.ts
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Expand Up @@ -3656,25 +3656,56 @@ fp.now(); // $ExpectType number

// _.throttle
{
const options: _.ThrottleSettings = {
const optionsLeading: _.ThrottleSettingsLeading = {
leading: true,
trailing: false,
}
const badOptionsLeading: _.ThrottleSettingsLeading = {
// @ts-expect-error lodash will treat an explicit undefined the same as `leading: false`
leading: undefined,
};
const optionsNoLeading: _.ThrottleSettings = {
leading: false,
};

const optionsAmbiguous = {
leading: true,
};
const boolean: boolean = false;
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nit: you might need false as boolean, otherwise TS will automatically narrow the type to false which is not what we want.

const maybeUndefined = (function (): true | undefined { return true })();
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Similar to above: a simpler way to do this might be something like:

const maybeUndefined: true | undefined = true as any;


const func = (a: number, b: string): boolean => true;

_.throttle(func); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func, 42); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func, 42, options); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_(func).throttle(); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42, options); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, options); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>

fp.throttle(42, func); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
fp.throttle(42)(func); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
_.throttle(func, 42); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
_.throttle(func, 42, {}); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
_.throttle(func, 42, { leading: true, trailing: false }); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
_.throttle(func, 42, { leading: false }); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func, 42, { leading: undefined }); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func, 42, { leading: boolean }); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_.throttle(func, 42, { leading: maybeUndefined }); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
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Also add a comment explaining why we should NOT expect DebouncedFuncLeading here, since this is probably surprising to everyone.

_.throttle(func, 42, optionsAmbiguous); // $ExpectType DebouncedFunc<(a: number, b: string) => boolean>
_(func).throttle(); // $ExpectType Function<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_(func).throttle(42); // $ExpectType Function<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_(func).throttle(42, {}); // $ExpectType Function<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_(func).throttle(42, { leading: true, trailing: false }); // $ExpectType Function<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_(func).throttle(42, { leading: false }); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42, { leading: undefined }); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42, { leading: boolean }); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42, { leading: maybeUndefined }); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_(func).throttle(42, optionsAmbiguous); // $ExpectType Function<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(); // $ExpectType FunctionChain<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_.chain(func).throttle(42); // $ExpectType FunctionChain<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, {}); // $ExpectType FunctionChain<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, { leading: true, trailing: false }); // $ExpectType FunctionChain<DebouncedFuncLeading<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, { leading: false }); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, { leading: undefined }); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, { leading: boolean }); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, { leading: maybeUndefined }); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>
_.chain(func).throttle(42, optionsAmbiguous); // $ExpectType FunctionChain<DebouncedFunc<(a: number, b: string) => boolean>>

fp.throttle(42, func); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
fp.throttle(42)(func); // $ExpectType DebouncedFuncLeading<(a: number, b: string) => boolean>
}

// _.unary
Expand Down