[fabric/core] convert AsyncResult to a class for improved usability and update Run functions to use AsyncResult

packages/fabric/core/result/async-result.ts

@@ -1,6 +1,6 @@
-// deno-lint-ignore-file no-namespace no-explicit-any
+// deno-lint-ignore-file no-namespace no-explicit-any no-async-promise-executor
+import { UnexpectedError } from "@fabric/core";
 import type { TaggedError } from "../error/tagged-error.ts";
-import { UnexpectedError } from "../error/unexpected-error.ts";
 import type { MaybePromise } from "../types/maybe-promise.ts";
 import { Result } from "./result.ts";
 
@@ -8,24 +8,123 @@ import { Result } from "./result.ts";
  * An AsyncResult represents the result of an asynchronous operation that can
  * resolve to a value of type `TValue` or an error of type `TError`.
  */
-export type AsyncResult<
+export class AsyncResult<
   TValue = any,
   TError extends TaggedError = never,
-> = Promise<Result<TValue, TError>>;
-
-export namespace AsyncResult {
-  export async function tryFrom<T, TError extends TaggedError>(
+> {
+  static tryFrom<T, TError extends TaggedError>(
     fn: () => MaybePromise<T>,
     errorMapper: (error: any) => TError,
   ): AsyncResult<T, TError> {
-    try {
-      return Result.succeedWith(await fn());
-    } catch (error) {
-      return Result.failWith(errorMapper(error));
-    }
+    return new AsyncResult(
+      new Promise<Result<T, TError>>(async (resolve) => {
+        try {
+          const value = await fn();
+          resolve(Result.ok(value));
+        } catch (error) {
+          resolve(Result.failWith(errorMapper(error)));
+        }
+      }),
+    );
   }
 
-  export function from<T>(fn: () => MaybePromise<T>): AsyncResult<T, never> {
-    return tryFrom(fn, (error) => new UnexpectedError(error) as never);
+  static from<T>(fn: () => MaybePromise<T>): AsyncResult<T, never> {
+    return AsyncResult.tryFrom(
+      fn,
+      (error) => new UnexpectedError(error) as never,
+    );
+  }
+
+  static ok<T>(value: T): AsyncResult<T, never> {
+    return new AsyncResult(Promise.resolve(Result.ok(value)));
+  }
+
+  static succeedWith = AsyncResult.ok;
+
+  static failWith<TError extends TaggedError>(
+    error: TError,
+  ): AsyncResult<never, TError> {
+    return new AsyncResult(Promise.resolve(Result.failWith(error)));
+  }
+
+  private constructor(private r: Promise<Result<TValue, TError>>) {
+  }
+
+  promise(): Promise<Result<TValue, TError>> {
+    return this.r;
+  }
+
+  async unwrapOrThrow(): Promise<TValue> {
+    return (await this.r).unwrapOrThrow();
+  }
+
+  async orThrow(): Promise<void> {
+    return (await this.r).orThrow();
+  }
+
+  async unwrapErrorOrThrow(): Promise<TError> {
+    return (await this.r).unwrapErrorOrThrow();
+  }
+
+  /**
+   * Map a function over the value of the result.
+   */
+  map<TMappedValue>(
+    fn: (value: TValue) => TMappedValue,
+  ): AsyncResult<TMappedValue, TError> {
+    return new AsyncResult(
+      this.r.then((result) => result.map(fn)),
+    );
+  }
+
+  /**
+   * Maps a function over the value of the result and flattens the result.
+   */
+  flatMap<TMappedValue, TMappedError extends TaggedError>(
+    fn: (value: TValue) => AsyncResult<TMappedValue, TMappedError>,
+  ): AsyncResult<TMappedValue, TError | TMappedError> {
+    return new AsyncResult(
+      this.r.then((result) => {
+        if (result.isError()) {
+          return result as any;
+        }
+
+        return (fn(result.unwrapOrThrow())).promise();
+      }),
+    );
+  }
+
+  /**
+   * Try to map a function over the value of the result.
+   * If the function throws an error, the result will be a failure.
+   */
+  tryMap<TMappedValue>(
+    fn: (value: TValue) => TMappedValue,
+    errMapper: (error: any) => TError,
+  ): AsyncResult<TMappedValue, TError> {
+    return new AsyncResult(
+      this.r.then((result) => result.tryMap(fn, errMapper)),
+    );
+  }
+
+  /**
+   * Map a function over the error of the result.
+   */
+  mapError<TMappedError extends TaggedError>(
+    fn: (error: TError) => TMappedError,
+  ): AsyncResult<TValue, TMappedError> {
+    return new AsyncResult(
+      this.r.then((result) => result.mapError(fn)),
+    );
+  }
+
+  /**
+   * Taps a function if the result is a success.
+   * This is useful for side effects that do not modify the result.
+   */
+  tap(fn: (value: TValue) => void): AsyncResult<TValue, TError> {
+    return new AsyncResult(
+      this.r.then((result) => result.tap(fn)),
+    );
   }
 }

packages/fabric/core/run/run.test.ts

@@ -1,27 +1,26 @@
-// deno-lint-ignore-file require-await
+import { AsyncResult } from "@fabric/core";
 import { describe, expect, test } from "@fabric/testing";
 import { UnexpectedError } from "../error/unexpected-error.ts";
-import { Result } from "../result/result.ts";
 import { Run } from "./run.ts";
 
 describe("Run", () => {
   describe("In Sequence", () => {
     test("should pipe the results of multiple async functions", async () => {
-      const result = await Run.seq(
-        async () => Result.succeedWith(1),
-        async (x) => Result.succeedWith(x + 1),
-        async (x) => Result.succeedWith(x * 2),
+      const result = Run.seq(
+        () => AsyncResult.succeedWith(1),
+        (x) => AsyncResult.succeedWith(x + 1),
+        (x) => AsyncResult.succeedWith(x * 2),
       );
 
-      expect(result.unwrapOrThrow()).toEqual(4);
+      expect(await result.unwrapOrThrow()).toEqual(4);
     });
 
     test("should return the first error if one of the functions fails", async () => {
       const result = await Run.seq(
-        async () => Result.succeedWith(1),
-        async () => Result.failWith(new UnexpectedError()),
-        async (x) => Result.succeedWith(x * 2),
-      );
+        () => AsyncResult.succeedWith(1),
+        () => AsyncResult.failWith(new UnexpectedError()),
+        (x) => AsyncResult.succeedWith(x * 2),
+      ).promise();
 
       expect(result.isError()).toBe(true);
     });

packages/fabric/core/run/run.ts

@@ -4,7 +4,7 @@ import type { AsyncResult } from "../result/async-result.ts";
 
 export namespace Run {
   // prettier-ignore
-  export async function seq<
+  export function seq<
     T1,
     TE1 extends TaggedError,
     T2,
@@ -14,7 +14,7 @@ export namespace Run {
     fn2: (value: T1) => AsyncResult<T2, TE2>,
   ): AsyncResult<T2, TE1 | TE2>;
   // prettier-ignore
-  export async function seq<
+  export function seq<
     T1,
     TE1 extends TaggedError,
     T2,
@@ -27,7 +27,7 @@ export namespace Run {
     fn3: (value: T2) => AsyncResult<T3, TE3>,
   ): AsyncResult<T3, TE1 | TE2 | TE3>;
   // prettier-ignore
-  export async function seq<
+  export function seq<
     T1,
     TE1 extends TaggedError,
     T2,
@@ -42,24 +42,20 @@ export namespace Run {
     fn3: (value: T2) => AsyncResult<T3, TE3>,
     fn4: (value: T3) => AsyncResult<T4, TE4>,
   ): AsyncResult<T4, TE1 | TE2 | TE3 | TE4>;
-  export async function seq(
+  export function seq(
     ...fns: ((...args: any[]) => AsyncResult<any, any>)[]
   ): AsyncResult<any, any> {
-    let result = await fns[0]!();
+    let result = fns[0]!();
 
     for (let i = 1; i < fns.length; i++) {
-      if (result.isError()) {
-        return result;
-      }
-
-      result = await fns[i]!(result.unwrapOrThrow());
+      result = result.flatMap((value) => fns[i]!(value));
     }
 
     return result;
   }
 
   // prettier-ignore
-  export async function seqUNSAFE<
+  export function seqOrThrow<
     T1,
     TE1 extends TaggedError,
     T2,
@@ -69,7 +65,7 @@ export namespace Run {
     fn2: (value: T1) => AsyncResult<T2, TE2>,
   ): Promise<T2>;
   // prettier-ignore
-  export async function seqUNSAFE<
+  export function seqOrThrow<
     T1,
     TE1 extends TaggedError,
     T2,
@@ -81,21 +77,11 @@ export namespace Run {
     fn2: (value: T1) => AsyncResult<T2, TE2>,
     fn3: (value: T2) => AsyncResult<T3, TE3>,
   ): Promise<T2>;
-  export async function seqUNSAFE(
+  export function seqOrThrow(
     ...fns: ((...args: any[]) => AsyncResult<any, any>)[]
   ): Promise<any> {
-    const result = await (seq as any)(...fns);
-
-    if (result.isError()) {
-      throw result.unwrapOrThrow();
-    }
+    const result = (seq as any)(...fns);
 
     return result.unwrapOrThrow();
   }
-
-  export async function UNSAFE<T, TError extends TaggedError>(
-    fn: () => AsyncResult<T, TError>,
-  ): Promise<T> {
-    return (await fn()).unwrapOrThrow();
-  }
 }