Node: path.format input properties are optional (#21003)

* Node: `path.format` input properties are optional

If `base` does not exist, `name` and `ext` will be used to compute it.

http://devdocs.io/node/path#path_path_format_pathobject

* Node: `FormatInputPathObject`: all properties are optional

* Node: add myself as author

* Avoid usage of `Partial`

types/node/index.d.ts

@@ -13,6 +13,7 @@
 //                 Deividas Bakanas <https://github.com/DeividasBakanas>
 //                 Kelvin Jin <https://github.com/kjin>
 //                 Alvis HT Tang <https://github.com/alvis>
+//                 Oliver Joseph Ash <https://github.com/OliverJAsh>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 /************************************************
@@ -4426,6 +4427,29 @@ declare module "path" {
         name: string;
     }
 
+    export interface FormatInputPathObject {
+        /**
+         * The root of the path such as '/' or 'c:\'
+         */
+        root?: string;
+        /**
+         * The full directory path such as '/home/user/dir' or 'c:\path\dir'
+         */
+        dir?: string;
+        /**
+         * The file name including extension (if any) such as 'index.html'
+         */
+        base?: string;
+        /**
+         * The file extension (if any) such as '.html'
+         */
+        ext?: string;
+        /**
+         * The file name without extension (if any) such as 'index'
+         */
+        name?: string;
+    }
+
     /**
      * Normalize a string path, reducing '..' and '.' parts.
      * When multiple slashes are found, they're replaced by a single one; when the path contains a trailing slash, it is preserved. On Windows backslashes are used.
@@ -4504,7 +4528,7 @@ declare module "path" {
      *
      * @param pathString path to evaluate.
      */
-    export function format(pathObject: ParsedPath): string;
+    export function format(pathObject: FormatInputPathObject): string;
 
     export module posix {
         export function normalize(p: string): string;

types/node/node-tests.ts

@@ -1651,6 +1651,15 @@ namespace path_tests {
     });
     // returns
     //    '/home/user/dir/file.txt'
+
+    path.format({
+        root: "/",
+        dir: "/home/user/dir",
+        ext: ".txt",
+        name: "file"
+    });
+    // returns
+    //    '/home/user/dir/file.txt'
 }
 
 ////////////////////////////////////////////////////