From 70956465acf34470fa1c362d6961bbf03bb4b5bb Mon Sep 17 00:00:00 2001
From: ExE Boss <3889017+ExE-Boss@users.noreply.github.com>
Date: Wed, 19 Feb 2020 20:13:44 +0100
Subject: [PATCH] =?UTF-8?q?feat(node):=20Add=C2=A0support=20for=C2=A0symbo?=
 =?UTF-8?q?l-based=20`CustomPromisify`=20(#42154)?=
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* feat(node): Add support for symbol-based `CustomPromisify`

* test(node): Add tests for symbol‑based `CustomPromisify`

* test(node): Fix `doSomething`’s `onSuccessCallback` defintion
---
 types/node/node-tests.ts | 11 ++++++++++-
 types/node/util.d.ts     | 21 +++++++++++++--------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/types/node/node-tests.ts b/types/node/node-tests.ts
index f9dcb5e19d..12c2bad9a5 100644
--- a/types/node/node-tests.ts
+++ b/types/node/node-tests.ts
@@ -130,7 +130,10 @@ import * as trace_events from "trace_events";
         const b: boolean = timeout.hasRef();
         timers.clearTimeout(timeout);
     }
-    async function testPromisify() {
+    async function testPromisify(doSomething: {
+        (foo: any, onSuccessCallback: (result: string) => void, onErrorCallback: (reason: any) => void): void;
+        [util.promisify.custom](foo: any): Promise<string>;
+    }) {
         const setTimeout = util.promisify(timers.setTimeout);
         let v: void = await setTimeout(100); // tslint:disable-line no-void-expression void-return
         let s: string = await setTimeout(100, "");
@@ -138,6 +141,12 @@ import * as trace_events from "trace_events";
         const setImmediate = util.promisify(timers.setImmediate);
         v = await setImmediate(); // tslint:disable-line no-void-expression
         s = await setImmediate("");
+
+        // $ExpectType (foo: any) => Promise<string>
+        const doSomethingPromise = util.promisify(doSomething);
+
+        // $ExpectType string
+        s = await doSomethingPromise('foo');
     }
 }
 
diff --git a/types/node/util.d.ts b/types/node/util.d.ts
index 85a5ad8138..e1507b9c81 100644
--- a/types/node/util.d.ts
+++ b/types/node/util.d.ts
@@ -60,10 +60,6 @@ declare module "util" {
     function deprecate<T extends Function>(fn: T, message: string, code?: string): T;
     function isDeepStrictEqual(val1: any, val2: any): boolean;
 
-    interface CustomPromisify<TCustom extends Function> extends Function {
-        __promisify__: TCustom;
-    }
-
     function callbackify(fn: () => Promise<void>): (callback: (err: NodeJS.ErrnoException) => void) => void;
     function callbackify<TResult>(fn: () => Promise<TResult>): (callback: (err: NodeJS.ErrnoException, result: TResult) => void) => void;
     function callbackify<T1>(fn: (arg1: T1) => Promise<void>): (arg1: T1, callback: (err: NodeJS.ErrnoException) => void) => void;
@@ -89,6 +85,16 @@ declare module "util" {
         fn: (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6) => Promise<TResult>
     ): (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: (err: NodeJS.ErrnoException | null, result: TResult) => void) => void;
 
+    interface CustomPromisifyLegacy<TCustom extends Function> extends Function {
+        __promisify__: TCustom;
+    }
+
+    interface CustomPromisifySymbol<TCustom extends Function> extends Function {
+        [promisify.custom]: TCustom;
+    }
+
+    type CustomPromisify<TCustom extends Function> = CustomPromisifySymbol<TCustom> | CustomPromisifyLegacy<TCustom>;
+
     function promisify<TCustom extends Function>(fn: CustomPromisify<TCustom>): TCustom;
     function promisify<TResult>(fn: (callback: (err: any, result: TResult) => void) => void): () => Promise<TResult>;
     function promisify(fn: (callback: (err?: any) => void) => void): () => Promise<void>;
@@ -111,6 +117,9 @@ declare module "util" {
         fn: (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: (err?: any) => void) => void,
     ): (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5) => Promise<void>;
     function promisify(fn: Function): Function;
+    namespace promisify {
+        const custom: unique symbol;
+    }
 
     namespace types {
         function isAnyArrayBuffer(object: any): boolean;
@@ -183,8 +192,4 @@ declare module "util" {
         encode(input?: string): Uint8Array;
         encodeInto(input: string, output: Uint8Array): EncodeIntoResult;
     }
-
-    namespace promisify {
-        const custom: unique symbol;
-    }
 }