std/node: add util.callbackify (#5415)

This adds [Node's `util.callbackify`][0] to `std/node/util.ts`.

I lifted most of this from the [original Node source code][1] (and [its
tests][2]). I tried to make minimal modifications to the source.

I made a few arbitrary decisions:

- I was unable to do the function's types elegantly. I made overloads
  for functions that have 0 to 5 (inclusive) arguments, excluding the
  callback. I would love to know a better way to do this. (It seems that
  the folks at DefinitelyTyped [were also stumped][3], though maybe
  their solution is deliberate.)
- There are a few edge cases that cause custom Node errors to be
  produced. Instead of re-implementing those errors completely, I
  created simplified classes. These are mostly correct but are not
  identical to the real Node errors.
- The tests implement a possibly-arcane `TestQueue` class. I originally
  used a lot of inline promises but found it too repetitive.

Closes [#5366][4].

[0]: https://nodejs.org/api/util.html#util_util_callbackify_original
[1]: https://github.com/nodejs/node/blob/47804933012841f2dc90626bdcc161adf34569a5/lib/util.js#L183-L226
[2]: https://github.com/nodejs/node/blob/47804933012841f2dc90626bdcc161adf34569a5/test/parallel/test-util-callbackify.js
[3]: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/7d24857ddb07ab637dfa8c477d13352f8a8206fc/types/node/util.d.ts#L61-L84
[4]: https://github.com/denoland/deno/issues/5366

3 files changed, 491 insertions, 0 deletions

diff --git a/std/node/_util/_util_callbackify.ts b/std/node/_util/_util_callbackify.ts
new file mode 100644
index 000000000..fdcaed526
--- /dev/null
+++ b/std/node/_util/_util_callbackify.ts
@@ -0,0 +1,125 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+//
+// Adapted from Node.js. Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+// These are simplified versions of the "real" errors in Node.
+class NodeFalsyValueRejectionError extends Error {
+  public reason: unknown;
+  public code = "ERR_FALSY_VALUE_REJECTION";
+  constructor(reason: unknown) {
+    super("Promise was rejected with falsy value");
+    this.reason = reason;
+  }
+}
+class NodeInvalidArgTypeError extends TypeError {
+  public code = "ERR_INVALID_ARG_TYPE";
+  constructor(argumentName: string) {
+    super(`The ${argumentName} argument must be of type function.`);
+  }
+}
+
+type Callback<ResultT> =
+  | ((err: Error) => void)
+  | ((err: null, result: ResultT) => void);
+
+function callbackify<ResultT>(
+  fn: () => PromiseLike<ResultT>
+): (callback: Callback<ResultT>) => void;
+function callbackify<ArgT, ResultT>(
+  fn: (arg: ArgT) => PromiseLike<ResultT>
+): (arg: ArgT, callback: Callback<ResultT>) => void;
+function callbackify<Arg1T, Arg2T, ResultT>(
+  fn: (arg1: Arg1T, arg2: Arg2T) => PromiseLike<ResultT>
+): (arg1: Arg1T, arg2: Arg2T, callback: Callback<ResultT>) => void;
+function callbackify<Arg1T, Arg2T, Arg3T, ResultT>(
+  fn: (arg1: Arg1T, arg2: Arg2T, arg3: Arg3T) => PromiseLike<ResultT>
+): (arg1: Arg1T, arg2: Arg2T, arg3: Arg3T, callback: Callback<ResultT>) => void;
+function callbackify<Arg1T, Arg2T, Arg3T, Arg4T, ResultT>(
+  fn: (
+    arg1: Arg1T,
+    arg2: Arg2T,
+    arg3: Arg3T,
+    arg4: Arg4T
+  ) => PromiseLike<ResultT>
+): (
+  arg1: Arg1T,
+  arg2: Arg2T,
+  arg3: Arg3T,
+  arg4: Arg4T,
+  callback: Callback<ResultT>
+) => void;
+function callbackify<Arg1T, Arg2T, Arg3T, Arg4T, Arg5T, ResultT>(
+  fn: (
+    arg1: Arg1T,
+    arg2: Arg2T,
+    arg3: Arg3T,
+    arg4: Arg4T,
+    arg5: Arg5T
+  ) => PromiseLike<ResultT>
+): (
+  arg1: Arg1T,
+  arg2: Arg2T,
+  arg3: Arg3T,
+  arg4: Arg4T,
+  arg5: Arg5T,
+  callback: Callback<ResultT>
+) => void;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function callbackify(original: any): any {
+  if (typeof original !== "function") {
+    throw new NodeInvalidArgTypeError('"original"');
+  }
+
+  const callbackified = function (this: unknown, ...args: unknown[]): void {
+    const maybeCb = args.pop();
+    if (typeof maybeCb !== "function") {
+      throw new NodeInvalidArgTypeError("last");
+    }
+    const cb = (...args: unknown[]): void => {
+      maybeCb.apply(this, args);
+    };
+    original.apply(this, args).then(
+      (ret: unknown) => {
+        setTimeout(cb.bind(this, null, ret), 0);
+      },
+      (rej: unknown) => {
+        rej = rej || new NodeFalsyValueRejectionError(rej);
+        queueMicrotask(cb.bind(this, rej));
+      }
+    );
+  };
+
+  const descriptors = Object.getOwnPropertyDescriptors(original);
+  // It is possible to manipulate a functions `length` or `name` property. This
+  // guards against the manipulation.
+  if (typeof descriptors.length.value === "number") {
+    descriptors.length.value++;
+  }
+  if (typeof descriptors.name.value === "string") {
+    descriptors.name.value += "Callbackified";
+  }
+  Object.defineProperties(callbackified, descriptors);
+  return callbackified;
+}
+
+export { callbackify };
diff --git a/std/node/_util/_util_callbackify_test.ts b/std/node/_util/_util_callbackify_test.ts
new file mode 100644
index 000000000..b4dcae755
--- /dev/null
+++ b/std/node/_util/_util_callbackify_test.ts
@@ -0,0 +1,364 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+//
+// Adapted from Node.js. Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+const { test } = Deno;
+import { assert, assertStrictEq } from "../../testing/asserts.ts";
+import { callbackify } from "./_util_callbackify.ts";
+
+const values = [
+  "hello world",
+  null,
+  undefined,
+  false,
+  0,
+  {},
+  { key: "value" },
+  Symbol("I am a symbol"),
+  function ok(): void {},
+  ["array", "with", 4, "values"],
+  new Error("boo"),
+];
+
+class TestQueue {
+  #waitingPromise: Promise<void>;
+  #resolve?: () => void;
+  #reject?: (err: unknown) => void;
+  #queueSize = 0;
+
+  constructor() {
+    this.#waitingPromise = new Promise((resolve, reject) => {
+      this.#resolve = resolve;
+      this.#reject = reject;
+    });
+  }
+
+  enqueue(fn: (done: () => void) => void): void {
+    this.#queueSize++;
+    try {
+      fn(() => {
+        this.#queueSize--;
+        if (this.#queueSize === 0) {
+          assert(
+            this.#resolve,
+            "Test setup error; async queue is missing #resolve"
+          );
+          this.#resolve();
+        }
+      });
+    } catch (err) {
+      assert(this.#reject, "Test setup error; async queue is missing #reject");
+      this.#reject(err);
+    }
+  }
+
+  waitForCompletion(): Promise<void> {
+    return this.#waitingPromise;
+  }
+}
+
+test("callbackify passes the resolution value as the second argument to the callback", async () => {
+  const testQueue = new TestQueue();
+
+  for (const value of values) {
+    // eslint-disable-next-line require-await
+    async function asyncFn(): Promise<typeof value> {
+      return value;
+    }
+    const cbAsyncFn = callbackify(asyncFn);
+    testQueue.enqueue((done) => {
+      cbAsyncFn((err: unknown, ret: unknown) => {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        done();
+      });
+    });
+
+    function promiseFn(): Promise<typeof value> {
+      return Promise.resolve(value);
+    }
+    const cbPromiseFn = callbackify(promiseFn);
+    testQueue.enqueue((done) => {
+      cbPromiseFn((err: unknown, ret: unknown) => {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        done();
+      });
+    });
+
+    function thenableFn(): PromiseLike<any> {
+      return {
+        then(onfulfilled): PromiseLike<any> {
+          assert(onfulfilled);
+          onfulfilled(value);
+          return this;
+        },
+      };
+    }
+    const cbThenableFn = callbackify(thenableFn);
+    testQueue.enqueue((done) => {
+      cbThenableFn((err: unknown, ret: unknown) => {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        done();
+      });
+    });
+  }
+
+  await testQueue.waitForCompletion();
+});
+
+test("callbackify passes the rejection value as the first argument to the callback", async () => {
+  const testQueue = new TestQueue();
+
+  for (const value of values) {
+    // eslint-disable-next-line require-await
+    async function asyncFn(): Promise<never> {
+      return Promise.reject(value);
+    }
+    const cbAsyncFn = callbackify(asyncFn);
+    assertStrictEq(cbAsyncFn.length, 1);
+    assertStrictEq(cbAsyncFn.name, "asyncFnCallbackified");
+    testQueue.enqueue((done) => {
+      cbAsyncFn((err: unknown, ret: unknown) => {
+        assertStrictEq(ret, undefined);
+        if (err instanceof Error) {
+          if ("reason" in err) {
+            assert(!value);
+            assertStrictEq((err as any).code, "ERR_FALSY_VALUE_REJECTION");
+            assertStrictEq((err as any).reason, value);
+          } else {
+            assertStrictEq(String(value).endsWith(err.message), true);
+          }
+        } else {
+          assertStrictEq(err, value);
+        }
+        done();
+      });
+    });
+
+    function promiseFn(): Promise<never> {
+      return Promise.reject(value);
+    }
+    const obj = {};
+    Object.defineProperty(promiseFn, "name", {
+      value: obj,
+      writable: false,
+      enumerable: false,
+      configurable: true,
+    });
+
+    const cbPromiseFn = callbackify(promiseFn);
+    assertStrictEq(promiseFn.name, obj);
+    testQueue.enqueue((done) => {
+      cbPromiseFn((err: unknown, ret: unknown) => {
+        assertStrictEq(ret, undefined);
+        if (err instanceof Error) {
+          if ("reason" in err) {
+            assert(!value);
+            assertStrictEq((err as any).code, "ERR_FALSY_VALUE_REJECTION");
+            assertStrictEq((err as any).reason, value);
+          } else {
+            assertStrictEq(String(value).endsWith(err.message), true);
+          }
+        } else {
+          assertStrictEq(err, value);
+        }
+        done();
+      });
+    });
+
+    function thenableFn(): PromiseLike<never> {
+      return {
+        then(onfulfilled, onrejected): PromiseLike<never> {
+          assert(onrejected);
+          onrejected(value);
+          return this;
+        },
+      };
+    }
+
+    const cbThenableFn = callbackify(thenableFn);
+    testQueue.enqueue((done) => {
+      cbThenableFn((err: unknown, ret: unknown) => {
+        assertStrictEq(ret, undefined);
+        if (err instanceof Error) {
+          if ("reason" in err) {
+            assert(!value);
+            assertStrictEq((err as any).code, "ERR_FALSY_VALUE_REJECTION");
+            assertStrictEq((err as any).reason, value);
+          } else {
+            assertStrictEq(String(value).endsWith(err.message), true);
+          }
+        } else {
+          assertStrictEq(err, value);
+        }
+        done();
+      });
+    });
+  }
+
+  await testQueue.waitForCompletion();
+});
+
+test("callbackify passes arguments to the original", async () => {
+  const testQueue = new TestQueue();
+
+  for (const value of values) {
+    // eslint-disable-next-line require-await
+    async function asyncFn<T>(arg: T): Promise<T> {
+      assertStrictEq(arg, value);
+      return arg;
+    }
+
+    const cbAsyncFn = callbackify(asyncFn);
+    assertStrictEq(cbAsyncFn.length, 2);
+    assert(Object.getPrototypeOf(cbAsyncFn) !== Object.getPrototypeOf(asyncFn));
+    assertStrictEq(Object.getPrototypeOf(cbAsyncFn), Function.prototype);
+    testQueue.enqueue((done) => {
+      cbAsyncFn(value, (err: unknown, ret: unknown) => {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        done();
+      });
+    });
+
+    function promiseFn<T>(arg: T): Promise<T> {
+      assertStrictEq(arg, value);
+      return Promise.resolve(arg);
+    }
+    const obj = {};
+    Object.defineProperty(promiseFn, "length", {
+      value: obj,
+      writable: false,
+      enumerable: false,
+      configurable: true,
+    });
+
+    const cbPromiseFn = callbackify(promiseFn);
+    assertStrictEq(promiseFn.length, obj);
+    testQueue.enqueue((done) => {
+      cbPromiseFn(value, (err: unknown, ret: unknown) => {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        done();
+      });
+    });
+  }
+
+  await testQueue.waitForCompletion();
+});
+
+test("callbackify preserves the `this` binding", async () => {
+  const testQueue = new TestQueue();
+
+  for (const value of values) {
+    const objectWithSyncFunction = {
+      fn(this: unknown, arg: typeof value): Promise<typeof value> {
+        assertStrictEq(this, objectWithSyncFunction);
+        return Promise.resolve(arg);
+      },
+    };
+    const cbSyncFunction = callbackify(objectWithSyncFunction.fn);
+    testQueue.enqueue((done) => {
+      cbSyncFunction.call(objectWithSyncFunction, value, function (
+        this: unknown,
+        err: unknown,
+        ret: unknown
+      ) {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        assertStrictEq(this, objectWithSyncFunction);
+        done();
+      });
+    });
+
+    const objectWithAsyncFunction = {
+      // eslint-disable-next-line require-await
+      async fn(this: unknown, arg: typeof value): Promise<typeof value> {
+        assertStrictEq(this, objectWithAsyncFunction);
+        return arg;
+      },
+    };
+    const cbAsyncFunction = callbackify(objectWithAsyncFunction.fn);
+    testQueue.enqueue((done) => {
+      cbAsyncFunction.call(objectWithAsyncFunction, value, function (
+        this: unknown,
+        err: unknown,
+        ret: unknown
+      ) {
+        assertStrictEq(err, null);
+        assertStrictEq(ret, value);
+        assertStrictEq(this, objectWithAsyncFunction);
+        done();
+      });
+    });
+  }
+
+  await testQueue.waitForCompletion();
+});
+
+test("callbackify throws with non-function inputs", () => {
+  ["foo", null, undefined, false, 0, {}, Symbol(), []].forEach((value) => {
+    try {
+      callbackify(value as any);
+      throw Error("We should never reach this error");
+    } catch (err) {
+      assert(err instanceof TypeError);
+      assertStrictEq((err as any).code, "ERR_INVALID_ARG_TYPE");
+      assertStrictEq(err.name, "TypeError");
+      assertStrictEq(
+        err.message,
+        'The "original" argument must be of type function.'
+      );
+    }
+  });
+});
+
+test("callbackify returns a function that throws if the last argument is not a function", () => {
+  // eslint-disable-next-line require-await
+  async function asyncFn(): Promise<number> {
+    return 42;
+  }
+
+  const cb = callbackify(asyncFn) as any;
+  const args: unknown[] = [];
+
+  ["foo", null, undefined, false, 0, {}, Symbol(), []].forEach((value) => {
+    args.push(value);
+
+    try {
+      cb(...args);
+      throw Error("We should never reach this error");
+    } catch (err) {
+      assert(err instanceof TypeError);
+      assertStrictEq((err as any).code, "ERR_INVALID_ARG_TYPE");
+      assertStrictEq(err.name, "TypeError");
+      assertStrictEq(
+        err.message,
+        "The last argument must be of type function."
+      );
+    }
+  });
+});
diff --git a/std/node/util.ts b/std/node/util.ts
index 73cbbf823..a61dc30b2 100644
--- a/std/node/util.ts
+++ b/std/node/util.ts
@@ -1,3 +1,5 @@
+export { callbackify } from "./_util/_util_callbackify.ts";
+
 export function isArray(value: unknown): boolean {
   return Array.isArray(value);
 }