2 files changed, 320 insertions, 0 deletions
diff --git a/std/node/_util/_util_promisify.ts b/std/node/_util/_util_promisify.ts
new file mode 100644
index 000000000..d7ca55be8
--- /dev/null
+++ b/std/node/_util/_util_promisify.ts
@@ -0,0 +1,105 @@
+// 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.
+
+// In addition to being accessible through util.promisify.custom,
+// this symbol is registered globally and can be accessed in any environment as Symbol.for('nodejs.util.promisify.custom')
+const kCustomPromisifiedSymbol = Symbol.for("nodejs.util.promisify.custom");
+// This is an internal Node symbol used by functions returning multiple arguments
+// e.g. ['bytesRead', 'buffer'] for fs.read.
+const kCustomPromisifyArgsSymbol = Symbol.for(
+  "deno.nodejs.util.promisify.customArgs"
+);
+
+class NodeInvalidArgTypeError extends TypeError {
+  public code = "ERR_INVALID_ARG_TYPE";
+  constructor(argumentName: string, type: string, received: unknown) {
+    super(
+      `The "${argumentName}" argument must be of type ${type}. Received ${typeof received}`
+    );
+  }
+}
+
+export function promisify(original: Function): Function {
+  if (typeof original !== "function")
+    throw new NodeInvalidArgTypeError("original", "Function", original);
+
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  if (original[kCustomPromisifiedSymbol]) {
+    // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+    const fn = original[kCustomPromisifiedSymbol];
+    if (typeof fn !== "function") {
+      throw new NodeInvalidArgTypeError(
+        "util.promisify.custom",
+        "Function",
+        fn
+      );
+    }
+    return Object.defineProperty(fn, kCustomPromisifiedSymbol, {
+      value: fn,
+      enumerable: false,
+      writable: false,
+      configurable: true,
+    });
+  }
+
+  // Names to create an object from in case the callback receives multiple
+  // arguments, e.g. ['bytesRead', 'buffer'] for fs.read.
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  const argumentNames = original[kCustomPromisifyArgsSymbol];
+
+  function fn(...args: unknown[]): Promise<unknown> {
+    return new Promise((resolve, reject) => {
+      // @ts-ignore
+      original.call(this, ...args, (err: Error, ...values: unknown[]) => {
+        if (err) {
+          return reject(err);
+        }
+        if (argumentNames !== undefined && values.length > 1) {
+          const obj = {};
+          for (let i = 0; i < argumentNames.length; i++) {
+            // @ts-ignore TypeScript
+            obj[argumentNames[i]] = values[i];
+          }
+          resolve(obj);
+        } else {
+          resolve(values[0]);
+        }
+      });
+    });
+  }
+
+  Object.setPrototypeOf(fn, Object.getPrototypeOf(original));
+
+  Object.defineProperty(fn, kCustomPromisifiedSymbol, {
+    value: fn,
+    enumerable: false,
+    writable: false,
+    configurable: true,
+  });
+  return Object.defineProperties(
+    fn,
+    Object.getOwnPropertyDescriptors(original)
+  );
+}
+
+promisify.custom = kCustomPromisifiedSymbol;
diff --git a/std/node/_util/_util_promisify_test.ts b/std/node/_util/_util_promisify_test.ts
new file mode 100644
index 000000000..a583d8cfe
--- /dev/null
+++ b/std/node/_util/_util_promisify_test.ts
@@ -0,0 +1,215 @@
+// 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.
+
+import {
+  assert,
+  assertEquals,
+  assertStrictEquals,
+  assertThrowsAsync,
+} from "../../testing/asserts.ts";
+
+import { promisify } from "./_util_promisify.ts";
+import * as fs from "../fs.ts";
+
+const { test } = Deno;
+
+const readFile = promisify(fs.readFile);
+const customPromisifyArgs = Symbol.for("deno.nodejs.util.promisify.customArgs");
+
+test("Errors should reject the promise", async function testPromiseRejection() {
+  await assertThrowsAsync(() => readFile("/dontexist"), Deno.errors.NotFound);
+});
+
+test("Promisify.custom", async function testPromisifyCustom() {
+  function fn(): void {}
+
+  function promisifedFn(): void {}
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  fn[promisify.custom] = promisifedFn;
+
+  const promisifiedFnA = promisify(fn);
+  const promisifiedFnB = promisify(promisifiedFnA);
+  assertStrictEquals(promisifiedFnA, promisifedFn);
+  assertStrictEquals(promisifiedFnB, promisifedFn);
+
+  await promisifiedFnA;
+  await promisifiedFnB;
+});
+
+test("promiisfy.custom symbol", function testPromisifyCustomSymbol() {
+  function fn(): void {}
+
+  function promisifiedFn(): void {}
+
+  // util.promisify.custom is a shared symbol which can be accessed
+  // as `Symbol.for("nodejs.util.promisify.custom")`.
+  const kCustomPromisifiedSymbol = Symbol.for("nodejs.util.promisify.custom");
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  fn[kCustomPromisifiedSymbol] = promisifiedFn;
+
+  assertStrictEquals(kCustomPromisifiedSymbol, promisify.custom);
+  assertStrictEquals(promisify(fn), promisifiedFn);
+  assertStrictEquals(promisify(promisify(fn)), promisifiedFn);
+});
+
+test("Invalid argument should throw", function testThrowInvalidArgument() {
+  function fn(): void {}
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  fn[promisify.custom] = 42;
+  try {
+    promisify(fn);
+  } catch (e) {
+    assertStrictEquals(e.code, "ERR_INVALID_ARG_TYPE");
+    assert(e instanceof TypeError);
+  }
+});
+
+test("Custom promisify args", async function testPromisifyCustomArgs() {
+  const firstValue = 5;
+  const secondValue = 17;
+
+  function fn(callback: Function): void {
+    callback(null, firstValue, secondValue);
+  }
+
+  // @ts-ignore TypeScript (as of 3.7) does not support indexing namespaces by symbol
+  fn[customPromisifyArgs] = ["first", "second"];
+
+  const obj = await promisify(fn)();
+  assertEquals(obj, { first: firstValue, second: secondValue });
+});
+
+test("Multiple callback args without custom promisify args", async function testPromisifyWithoutCustomArgs() {
+  function fn(callback: Function): void {
+    callback(null, "foo", "bar");
+  }
+  const value = await promisify(fn)();
+  assertStrictEquals(value, "foo");
+});
+
+test("Undefined resolved value", async function testPromisifyWithUndefinedResolvedValue() {
+  function fn(callback: Function): void {
+    callback(null);
+  }
+  const value = await promisify(fn)();
+  assertStrictEquals(value, undefined);
+});
+
+test("Undefined resolved value II", async function testPromisifyWithUndefinedResolvedValueII() {
+  function fn(callback: Function): void {
+    callback();
+  }
+  const value = await promisify(fn)();
+  assertStrictEquals(value, undefined);
+});
+
+test("Resolved value: number", async function testPromisifyWithNumberResolvedValue() {
+  function fn(err: Error | null, val: number, callback: Function): void {
+    callback(err, val);
+  }
+  const value = await promisify(fn)(null, 42);
+  assertStrictEquals(value, 42);
+});
+
+test("Rejected value", async function testPromisifyWithNumberRejectedValue() {
+  function fn(err: Error | null, val: null, callback: Function): void {
+    callback(err, val);
+  }
+  await assertThrowsAsync(
+    () => promisify(fn)(new Error("oops"), null),
+    Error,
+    "oops"
+  );
+});
+
+test("Rejected value", async function testPromisifyWithAsObjectMethod() {
+  const o: { fn?: Function } = {};
+  const fn = promisify(function (cb: Function): void {
+    // @ts-ignore TypeScript
+    cb(null, this === o);
+  });
+
+  o.fn = fn;
+
+  const val = await o.fn();
+  assert(val);
+});
+
+test("Multiple callback", async function testPromisifyWithMultipleCallback() {
+  const err = new Error("Should not have called the callback with the error.");
+  const stack = err.stack;
+
+  const fn = promisify(function (cb: Function): void {
+    cb(null);
+    cb(err);
+  });
+
+  await fn();
+  await Promise.resolve();
+  return assertStrictEquals(stack, err.stack);
+});
+
+test("Promisify a promise", function testPromisifyPromise() {
+  function c(): void {}
+  const a = promisify(function (): void {});
+  const b = promisify(a);
+  assert(c !== a);
+  assertStrictEquals(a, b);
+});
+
+test("Test error", async function testInvalidArguments() {
+  let errToThrow;
+
+  const thrower = promisify(function (
+    a: number,
+    b: number,
+    c: number,
+    cb: Function
+  ): void {
+    errToThrow = new Error(`${a}-${b}-${c}-${cb}`);
+    throw errToThrow;
+  });
+
+  try {
+    await thrower(1, 2, 3);
+    throw new Error(`should've failed`);
+  } catch (e) {
+    assertStrictEquals(e, errToThrow);
+  }
+});
+
+test("Test invalid arguments", function testInvalidArguments() {
+  [undefined, null, true, 0, "str", {}, [], Symbol()].forEach((input) => {
+    try {
+      // @ts-ignore TypeScript
+      promisify(input);
+    } catch (e) {
+      assertStrictEquals(e.code, "ERR_INVALID_ARG_TYPE");
+      assert(e instanceof TypeError);
+      assertEquals(
+        e.message,
+        `The "original" argument must be of type Function. Received ${typeof input}`
+      );
+    }
+  });
+});