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filter over Map #136

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5 changes: 5 additions & 0 deletions test/filter.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -90,3 +90,8 @@ expectType<(number | undefined)[]>(filter(x => x != null, [] as (number | undefi
// filter(() => narrow, dist)
// no need for type annotations when using full signature
expectType<Record<string, string>>(filter(isNotNil, {} as Dict));


// filter(() => narrow)(dist)
expectType<Map<string, string>>(filter(isNotNil, new Map<string, string | undefined>()));
expectType<Map<string, number>>(filter(gt5, new Map<string, number>()));
Comment on lines +95 to +97
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First, these tests are for // filter(() => narrow, map)

Second, you need to be far more exhaustive with your test additions. This file has test coverage for all curry varieties and argument type overloads. You added support for a new argument type, so you need to add tests for each curry call variation

12 changes: 10 additions & 2 deletions types/filter.d.ts
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Expand Up @@ -10,10 +10,18 @@ export function filter<A, P extends A>(
<B extends A>(list: readonly B[]): P[];
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Github doesn't let you add suggests to unchanged code, but you need to add type support for Map here too. This whole things should be:

// filter(() => narrow)
export function filter<A, P extends A>(
  pred: (val: A) => val is P,
): {
  // filter(() => narrow)(map)
  <K, B extends A>(map: Map<K, B>): Map<K, P>;
  // if we put `Record<string, A>` first, it will actually pic`A[]` as well
  // so it needs to go first
  // filter(() => narrow)(list)
  <B extends A>(list: readonly B[]): P[];
  // filter(() => narrow)(dict)
  <B extends A>(dict: Record<string, B>): Record<string, P>;
  // but we also want `A[]` to be the default when doing `pipe(filter(fn))`, so it also needs to be last
  // filter(() => narrow)(list | dict)
  <B extends A>(list: readonly B[]): P[];
};

};

// filter(() => boolean)
// filter(() => boolean)(list | dict)
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Suggested change
// filter(() => boolean)(list | dict)
// filter(() => boolean)

export function filter<T>(
pred: (value: T) => boolean,
): <P extends T, C extends readonly P[] | Record<string, P>>(collection: C) => C;
): {
<K>(map: Map<K, T>): Map<K, T>;
<P extends T, C extends readonly P[] | Record<string, P>>(collection: C): C;
Comment on lines +17 to +18
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Suggested change
<K>(map: Map<K, T>): Map<K, T>;
<P extends T, C extends readonly P[] | Record<string, P>>(collection: C): C;
// filter(() => boolean)(map)
<K>(map: Map<K, T>): Map<K, T>;
// filter(() => boolean)(list | dict)
<P extends T, C extends readonly P[] | Record<string, P>>(collection: C): C;

};

// filter(() => narrow, map)
export function filter<K, T, P extends T>(pred: (val: T) => val is P, map: Map<K, T>): Map<K, P>;
// filter(() => boolean, map)
export function filter<K, T>(pred: (val: T) => boolean, map: Map<K, T>): Map<K, T>;

// filter(() => narrow, list) - readonly T[] falls into Record<string T> for some reason, so list needs to come first
export function filter<T, P extends T>(pred: (val: T) => val is P, list: readonly T[]): P[];
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