feat(infra): livedata effect

packages/common/infra/src/livedata/effect/__tests__/effect.spec.ts

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+import type { Subscriber } from 'rxjs';
+import { from, Observable, switchMap } from 'rxjs';
+import { beforeEach, describe, expect, test, vi } from 'vitest';
+
+import {
+  catchErrorInto,
+  effect,
+  LiveData,
+  mapInto,
+  onComplete,
+  onStart,
+} from '../../';
+
+describe('example', () => {
+  type User = {
+    id: number;
+    name: string;
+  };
+
+  const fetchUser = vi.fn<[number], Promise<User>>();
+
+  const user$ = new LiveData<User | null>(null);
+  const isLoading$ = new LiveData<boolean>(false);
+  const error$ = new LiveData<Error | null>(null);
+
+  const loadUser = effect(
+    switchMap((id: number) =>
+      from(fetchUser(id)).pipe(
+        mapInto(user$),
+        catchErrorInto(error$),
+        onStart(() => isLoading$.next(true)),
+        onComplete(() => isLoading$.next(false))
+      )
+    )
+  );
+
+  beforeEach(() => {
+    fetchUser.mockClear();
+
+    user$.next(null);
+    isLoading$.next(false);
+    error$.next(null);
+  });
+
+  test('basic', async () => {
+    fetchUser.mockImplementation(async id => ({ id, name: 'John' }));
+    loadUser(1);
+    await vi.waitFor(() =>
+      expect(user$.value).toStrictEqual({ id: 1, name: 'John' })
+    );
+    expect(fetchUser).toHaveBeenCalledOnce();
+    expect(fetchUser).toHaveBeenCalledWith(1);
+  });
+
+  test('error', async () => {
+    fetchUser.mockRejectedValue(new Error('some error'));
+    loadUser(1);
+    await vi.waitFor(() => expect(error$.value).toBeInstanceOf(Error));
+  });
+
+  test('isLoading', async () => {
+    let resolveFn: (value: User) => void = null!;
+    fetchUser.mockReturnValue(
+      new Promise(resolve => {
+        resolveFn = resolve;
+      })
+    );
+    loadUser(1);
+    await vi.waitFor(() => expect(isLoading$.value).toBe(true));
+    expect(fetchUser).toHaveBeenCalledOnce();
+    resolveFn({ id: 1, name: 'John' });
+    await vi.waitFor(() => expect(isLoading$.value).toBe(false));
+  });
+
+  test('switchMap', async () => {
+    let fetch1: Subscriber<User> = null!;
+    let fetch1Canceled = false;
+    fetchUser.mockReturnValue(
+      new Observable<User>(subscriber => {
+        fetch1 = subscriber;
+        return () => {
+          fetch1Canceled = true;
+        };
+      }) as any
+    );
+
+    loadUser(1);
+    await vi.waitFor(() => expect(fetch1).toBeTruthy());
+    expect(isLoading$.value).toBe(true);
+
+    // start fetch2, should cancel fetch1
+    let fetch2: Subscriber<User> = null!;
+    fetchUser.mockReturnValue(
+      new Observable<User>(subscriber => {
+        fetch2 = subscriber;
+      }) as any
+    );
+    loadUser(2);
+    await vi.waitFor(() => expect(fetch1Canceled).toBe(true));
+    expect(isLoading$.value).toBe(true);
+
+    // fetch1 fail, should not affect fetch2
+    fetch1.error(new Error('some error'));
+    expect(error$.value).toBe(null);
+
+    // make fetch2 complete
+    fetch2.next({ id: 2, name: 'John' });
+    fetch2.complete();
+
+    // should update user$ to fetch2 result
+    await vi.waitFor(() =>
+      expect(user$.value).toStrictEqual({ id: 2, name: 'John' })
+    );
+    // should not have error
+    expect(error$.value).toBe(null);
+    expect(isLoading$.value).toBe(false);
+  });
+});

packages/common/infra/src/livedata/effect/index.ts

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+import { DebugLogger } from '@affine/debug';
+import { Unreachable } from '@affine/env/constant';
+import { type OperatorFunction, Subject } from 'rxjs';
+
+const logger = new DebugLogger('effect');
+
+export interface Effect<T> {
+  (value: T): void;
+}
+
+export function effect<T, A>(op1: OperatorFunction<T, A>): Effect<T>;
+export function effect<T, A, B>(
+  op1: OperatorFunction<T, A>,
+  op2: OperatorFunction<A, B>
+): Effect<T>;
+export function effect<T, A, B, C>(
+  op1: OperatorFunction<T, A>,
+  op2: OperatorFunction<A, B>,
+  op3: OperatorFunction<B, C>
+): Effect<T>;
+export function effect<T, A, B, C, D>(
+  op1: OperatorFunction<T, A>,
+  op2: OperatorFunction<A, B>,
+  op3: OperatorFunction<B, C>,
+  op4: OperatorFunction<C, D>
+): Effect<T>;
+export function effect<T, A, B, C, D, E>(
+  op1: OperatorFunction<T, A>,
+  op2: OperatorFunction<A, B>,
+  op3: OperatorFunction<B, C>,
+  op4: OperatorFunction<C, D>,
+  op5: OperatorFunction<D, E>
+): Effect<T>;
+export function effect<T, A, B, C, D, E, F>(
+  op1: OperatorFunction<T, A>,
+  op2: OperatorFunction<A, B>,
+  op3: OperatorFunction<B, C>,
+  op4: OperatorFunction<C, D>,
+  op5: OperatorFunction<D, E>,
+  op6: OperatorFunction<E, F>
+): Effect<T>;
+export function effect(...args: any[]) {
+  const subject$ = new Subject<any>();
+
+  // eslint-disable-next-line prefer-spread
+  subject$.pipe.apply(subject$, args as any).subscribe({
+    next(value) {
+      logger.error('effect should not emit value', value);
+      throw new Unreachable('effect should not emit value');
+    },
+    complete() {
+      logger.error('effect unexpected complete');
+      throw new Unreachable('effect unexpected complete');
+    },
+    error(error) {
+      logger.error('effect uncatched error', error);
+      throw new Unreachable('effect uncatched error');
+    },
+  });
+
+  return ((value: unknown) => {
+    subject$.next(value);
+  }) as never;
+}