Issue with typescript 4.1

[flovilmart]

Problem description

Since typescript 4.1, the promise resolution typing has changed.
This change is documented here and well known.

Reproduction steps

Opened the following branch to demonstrate the issue.

Running npm install or npm run compile

> @grpc/[email protected] compile /Users/florentvilmart/src/grpc/grpc-node/packages/grpc-js
> tsc -p .

src/call-credentials.ts:118:23 - error TS2345: Argument of type '{ [index: string]: string; } | undefined' is not assignable to parameter of type '{ [index: string]: string; } | PromiseLike<{ [index: string]: string; }>'.
  Type 'undefined' is not assignable to type '{ [index: string]: string; } | PromiseLike<{ [index: string]: string; }>'.

118               resolve(headers);
                          ~~~~~~~

src/server-call.ts:511:13 - error TS2794: Expected 1 arguments, but got 0. Did you forget to include 'void' in your type argument to 'Promise'?

511             resolve();
                ~~~~~~~~~

  node_modules/typescript/lib/lib.es2015.promise.d.ts:33:34
    33     new <T>(executor: (resolve: (value: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void): Promise<T>;
                                        ~~~~~~~~~~~~~~~~~~~~~~~~~
    An argument for 'value' was not provided.

src/server-call.ts:518:11 - error TS2794: Expected 1 arguments, but got 0. Did you forget to include 'void' in your type argument to 'Promise'?

518           resolve();
              ~~~~~~~~~

  node_modules/typescript/lib/lib.es2015.promise.d.ts:33:34
    33     new <T>(executor: (resolve: (value: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void): Promise<T>;
                                        ~~~~~~~~~~~~~~~~~~~~~~~~~
    An argument for 'value' was not provided.

Environment

• Mac OS 11.2.3
• Node version v14.15.0
• Package name and version [@grpc/[email protected]]

[flovilmart]

Closing as not applicable and #1807 is exposing the proper interface now