async-collection-utils/.aider.chat.history.md

A well tested and typed collection of map, forEach, reduce, filter etc. utility functions supporting arrays, sets, maps, plain objects, iterators in both async and synchronous versions.

# aider chat started at 2025-07-07 21:04:37

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#### /add src/asyncMap.ts  
> Added src/asyncMap.ts to the chat  

#### /add src/asyncMap.test.ts  
> Added src/asyncMap.test.ts to the chat  

#### /code implement asyncFilter, try to follow as closely as possible a pattern set in asyncMap and asyncFlatMap utilities  

#### implement asyncFilter, try to follow as closely as possible a pattern set in asyncMap and asyncFlatMap utilities  

src/asyncFilter.ts
````typescript
<<<<<<< SEARCH
=======
import {
  Break,
  CustomAsyncIterable,
  CustomIterable,
  isPlainObject,
  LastClass,
  TypedArray,
} from "./shared";

/**
 * Asynchronously filters different kinds of iterables/collections.
 * The predicate can short-circuit by returning `Break` or
 * keep the current item and stop by returning `Last(value)`.
 */

/* ──────────────────────────── Array ──────────────────────────── */
export async function asyncFilter<TCollection extends unknown[]>(
  array: TCollection,
  predicate: (
    item: TCollection extends Array<infer TValue> ? TValue : never,
    index: number,
    arr: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<TCollection extends Array<infer TValue> ? TValue : never>
  >,
): Promise<Array<TCollection[number]>>;

/* ───────────────────────────── Set ───────────────────────────── */
export async function asyncFilter<TCollection extends Set<unknown>>(
  set: TCollection,
  predicate: (
    item: TCollection extends Set<infer TValue> ? TValue : never,
    index: number,
    set: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<TCollection extends Set<infer TValue> ? TValue : never>
  >,
): Promise<Set<TCollection extends Set<infer TValue> ? TValue : never>>;

/* ───────────────────────────── Map ───────────────────────────── */
export async function asyncFilter<TCollection extends Map<unknown, unknown>>(
  map: TCollection,
  predicate: (
    value: TCollection extends Map<unknown, infer TValue> ? TValue : never,
    key: TCollection extends Map<infer TKey, unknown> ? TKey : never,
    map: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<TCollection extends Map<unknown, infer TValue> ? TValue : never>
  >,
): Promise<
  Map<
    TCollection extends Map<infer TKey, unknown> ? TKey : never,
    TCollection extends Map<unknown, infer TValue> ? TValue : never
  >
>;

/* ───────────────────────── TypedArray ────────────────────────── */
export async function asyncFilter<TCollection extends TypedArray>(
  typedArray: TCollection,
  predicate: (
    item: TCollection[number],
    index: number,
    arr: TCollection,
  ) => Promise<boolean | typeof Break | LastClass<TCollection[number]>>,
): Promise<TCollection>;

/* ──────────────────────── Custom Iterable ────────────────────── */
export async function asyncFilter<
  TCollection extends CustomIterable<unknown, unknown>,
>(
  iterable: TCollection,
  predicate: (
    item: TCollection extends CustomIterable<infer TValue, unknown>
      ? TValue
      : never,
    index: number,
    iterable: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<
        TCollection extends CustomIterable<infer TValue, unknown>
          ? TValue
          : never
      >
  >,
): Promise<
  AsyncGenerator<
    TCollection extends CustomIterable<infer TValue, unknown> ? TValue : never
  >
>;

/* ────────────────────── Custom AsyncIterable ─────────────────── */
export async function asyncFilter<
  TCollection extends CustomAsyncIterable<unknown, unknown>,
>(
  asyncIterable: TCollection,
  predicate: (
    item: TCollection extends CustomAsyncIterable<infer TValue, unknown>
      ? TValue
      : never,
    index: number,
    iterable: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<
        TCollection extends CustomAsyncIterable<infer TValue, unknown>
          ? TValue
          : never
      >
  >,
): Promise<
  AsyncGenerator<
    TCollection extends CustomAsyncIterable<infer TValue, unknown>
      ? TValue
      : never
  >
>;

/* ───────────────────────── Plain Object ──────────────────────── */
export async function asyncFilter<
  TCollection extends Record<string | number | symbol, unknown>,
>(
  obj: TCollection,
  predicate: (
    value: TCollection[keyof TCollection],
    key: keyof TCollection & string,
    object: TCollection,
  ) => Promise<
    | boolean
    | typeof Break
    | LastClass<TCollection[keyof TCollection]>
  >,
): Promise<{ [K in keyof TCollection]: TCollection[K] }>;

/* ───────────────────────── Default impl ──────────────────────── */
export async function asyncFilter(
  iterable: unknown,
  predicate: (...args: any[]) => Promise<unknown>,
): Promise<unknown> {
  /* ───── Array ───── */
  if (Array.isArray(iterable)) {
    const result: unknown[] = [];
    for (let i = 0; i < iterable.length; i++) {
      const decision = await predicate(iterable[i], i, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        result.push(decision.value);
        break;
      }
      if (decision) result.push(iterable[i]);
    }
    return result;
  }

  /* ───── Set ───── */
  if (iterable instanceof Set) {
    const result = new Set();
    let i = 0;
    for (const item of iterable) {
      const decision = await predicate(item, i++, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        result.add(decision.value);
        break;
      }
      if (decision) result.add(item);
    }
    return result;
  }

  /* ───── Map ───── */
  if (iterable instanceof Map) {
    const result = new Map();
    for (const [key, value] of iterable) {
      const decision = await predicate(value, key, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        result.set(key, decision.value);
        break;
      }
      if (decision) result.set(key, value);
    }
    return result;
  }

  /* ───── TypedArray ───── */
  if (ArrayBuffer.isView(iterable)) {
    const Ctor = iterable.constructor as any;
    const buffer: unknown[] = [];
    let i = 0;
    for (const value of iterable as TypedArray) {
      const decision = await predicate(value, i++, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        buffer.push(decision.value);
        break;
      }
      if (decision) buffer.push(value);
    }
    return new Ctor(buffer);
  }

  /* ───── Plain Object ───── */
  if (isPlainObject(iterable)) {
    const result: Record<string, unknown> = {};
    for (const key of Object.keys(iterable)) {
      const decision = await predicate(iterable[key], key, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        result[key] = decision.value;
        break;
      }
      if (decision) result[key] = iterable[key];
    }
    return result;
  }

  /* ───── (Async)Iterators ───── */
  async function* generator() {
    let i = 0;
    for await (const item of iterable as Iterable<unknown>) {
      const decision = await predicate(item, i++, iterable);
      if (decision === Break) break;
      if (decision instanceof LastClass) {
        yield decision.value;
        break;
      }
      if (decision) yield item;
    }
  }

  return generator();
}
>>>>>>> REPLACE
````

Suggested shell commands:
```bash
bun test
```

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> src/asyncFilter.ts  
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#### /exit  

# aider chat started at 2025-07-07 21:15:47

> /Users/lukasz/.local/bin/aider --model o3 --reasoning-effort high --weak-model gpt-4.1-mini --watch --no-auto-commits  
> Warning: Streaming is not supported by o3. Disabling streaming.  
> Error: Read-only file /Users/lukasz/Dev/_NEW/async-collection-utils/aider-conventions.md does not exist. Skipping.  
> Aider v0.85.1  
> Main model: o3 with diff edit format, reasoning high  
> Weak model: gpt-4.1-mini  
> Git repo: .git with 31 files  
> Repo-map: using 4096 tokens, auto refresh  
> Added ../../../aider-conventions.md to the chat (read-only).  

#### /add src/asyncFilter.ts src/asyncMap.ts src/asyncMap.test.ts  
> Added src/asyncFilter.ts to the chat  
> Added src/asyncMap.test.ts to the chat  
> Added src/asyncMap.ts to the chat  

#### /code write tests for asyncFilter function. Follow very closely the pattern in existing tests e.g. in asyncMap.test.ts.  

#### write tests for asyncFilter function. Follow very closely the pattern in existing tests e.g. in asyncMap.test.ts.  

src/asyncFilter.test.ts
````typescript
<<<<<<< SEARCH
=======
import { asyncFilter } from "./asyncFilter";
import { Break, Last } from "./shared";

describe("asyncFilter", () => {
  /* ───────────────────────── Array ───────────────────────── */
  describe("array", () => {
    it("should filter values", async () => {
      const result = await asyncFilter([1, 2, 3], async (value) => value % 2 === 0);
      expect(result).toStrictEqual([2]);
    });

    it("should break on encountering Break", async () => {
      const result = await asyncFilter([1, 2, 3], async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });
      expect(result).toStrictEqual([2]);
    });

    it("should save value and break on encountering Last", async () => {
      const result = await asyncFilter([1, 2, 3], async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });
      expect(result).toStrictEqual([2, 30]);
    });
  });

  /* ───────────────────────── Set ───────────────────────── */
  describe("set", () => {
    it("should filter values", async () => {
      const result = await asyncFilter(new Set([1, 2, 3]), async (value) => value % 2 === 0);
      expect(result).toStrictEqual(new Set([2]));
    });

    it("should break on encountering Break", async () => {
      const result = await asyncFilter(new Set([1, 2, 3]), async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });
      expect(result).toStrictEqual(new Set([2]));
    });

    it("should save value and break on encountering Last", async () => {
      const result = await asyncFilter(new Set([1, 2, 3]), async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });
      expect(result).toStrictEqual(new Set([2, 30]));
    });
  });

  /* ───────────────────────── Map ───────────────────────── */
  describe("map", () => {
    const inputMap = new Map([
      [1, 1],
      [2, 2],
      [3, 3],
    ]);

    it("should filter values", async () => {
      const result = await asyncFilter(inputMap, async (value) => value % 2 === 0);
      expect(result).toStrictEqual(new Map([[2, 2]]));
    });

    it("should break on encountering Break", async () => {
      const result = await asyncFilter(inputMap, async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });
      expect(result).toStrictEqual(new Map([[2, 2]]));
    });

    it("should save value and break on encountering Last", async () => {
      const result = await asyncFilter(inputMap, async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });
      expect(result).toStrictEqual(
        new Map([
          [2, 2],
          [3, 30],
        ]),
      );
    });
  });

  /* ─────────────────────── TypedArray ─────────────────────── */
  describe("typedArray", () => {
    it("should filter values", async () => {
      const uint8 = new Uint8Array(3);
      uint8[0] = 1;
      uint8[1] = 2;
      uint8[2] = 3;

      const result = await asyncFilter(uint8, async (value) => value % 2 === 0);

      const expectedUint8 = new Uint8Array(1);
      expectedUint8[0] = 2;
      expect(result).toStrictEqual(expectedUint8);
    });

    it("should break on encountering Break", async () => {
      const uint8 = new Uint8Array(3);
      uint8[0] = 1;
      uint8[1] = 2;
      uint8[2] = 3;

      const result = await asyncFilter(uint8, async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });

      const expectedUint8 = new Uint8Array(1);
      expectedUint8[0] = 2;
      expect(result).toStrictEqual(expectedUint8);
    });

    it("should save value and break on encountering Last", async () => {
      const uint8 = new Uint8Array(3);
      uint8[0] = 1;
      uint8[1] = 2;
      uint8[2] = 3;

      const result = await asyncFilter(uint8, async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });

      const expectedUint8 = new Uint8Array(2);
      expectedUint8[0] = 2;
      expectedUint8[1] = 30;
      expect(result).toStrictEqual(expectedUint8);
    });
  });

  /* ───────────────────── Plain Object ───────────────────── */
  describe("plain object", () => {
    const input = { "1": 1, "2": 2, "3": 3 };

    it("should filter values", async () => {
      const result = await asyncFilter(input, async (value) => value % 2 === 0);
      expect(result).toStrictEqual({ "2": 2 });
    });

    it("should break on encountering Break", async () => {
      const result = await asyncFilter(input, async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });
      expect(result).toStrictEqual({ "2": 2 });
    });

    it("should save value and break on encountering Last", async () => {
      const result = await asyncFilter(input, async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });
      expect(result).toStrictEqual({ "2": 2, "3": 30 });
    });
  });

  /* ───────────────────────── Iterator ───────────────────────── */
  describe("iterator", () => {
    it("should filter values", async () => {
      const iterator = new Set([1, 2, 3]).values();
      const result = await asyncFilter(iterator, async (value) => value % 2 === 0);

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2]);
    });

    it("should break on encountering Break", async () => {
      const iterator = new Set([1, 2, 3]).values();
      const result = await asyncFilter(iterator, async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2]);
    });

    it("should save value and break on encountering Last", async () => {
      const iterator = new Set([1, 2, 3]).values();
      const result = await asyncFilter(iterator, async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2, 30]);
    });
  });

  /* ─────────────────────── AsyncIterator ─────────────────────── */
  describe("asyncIterator", () => {
    it("should filter values", async () => {
      const asyncIterator = (async function* (): AsyncGenerator<number, void, void> {
        yield 1;
        yield 2;
        yield 3;
      })();

      const result = await asyncFilter(asyncIterator, async (value) => value % 2 === 0);

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2]);
    });

    it("should break on encountering Break", async () => {
      const asyncIterator = (async function* (): AsyncGenerator<number, void, void> {
        yield 1;
        yield 2;
        yield 3;
      })();

      const result = await asyncFilter(asyncIterator, async (value) => {
        if (value === 3) return Break;
        return value % 2 === 0;
      });

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2]);
    });

    it("should save value and break on encountering Last", async () => {
      const asyncIterator = (async function* (): AsyncGenerator<number, void, void> {
        yield 1;
        yield 2;
        yield 3;
      })();

      const result = await asyncFilter(asyncIterator, async (value) => {
        if (value === 3) return Last(value * 10);
        return value % 2 === 0;
      });

      const resultArray: number[] = [];
      for await (const value of result) {
        resultArray.push(value as number);
      }
      expect(resultArray).toStrictEqual([2, 30]);
    });
  });
});
>>>>>>> REPLACE
````

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