parse-prefer-header: More specific typings (#42642)

* parse-prefer-header: Allow null or undefined input

* parse-prefer-header: More explicit return value typing

* parse-prefer-header: amend contributor list

* parse-prefer-header: Support ReadonlyArray argument

* parse-prefer-header: Add separate tests for Array and ReadonlyArray

types/parse-prefer-header/index.d.ts

@@ -1,8 +1,8 @@
 // Type definitions for parse-prefer-header 1.0
 // Project: https://github.com/ppaskaris/node-parse-prefer-header
-// Definitions by: Vincenzo Chianese <https://github.com/XVincentX>
+// Definitions by: Vincenzo Chianese <https://github.com/XVincentX>, Marcell Toth <https://github.com/marcelltoth>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
-declare function parsePreferHeader(preferHeader: string | string[]): { [key: string]: string | boolean };
+declare function parsePreferHeader(preferHeader: string | ReadonlyArray<string> | null | undefined): { [key: string]: string | true };
 
 export = parsePreferHeader;

types/parse-prefer-header/parse-prefer-header-tests.ts

@@ -1,4 +1,11 @@
 import parsePreferHeader = require('parse-prefer-header');
 
-parsePreferHeader(['respond-async, wait=100', 'handling=lenient']);
+const testArray = ['respond-async, wait=100', 'handling=lenient'];
+
+const readonlyTestArray: ReadonlyArray<string> = testArray;
+
+parsePreferHeader(testArray);
+parsePreferHeader(readonlyTestArray);
 parsePreferHeader('');
+parsePreferHeader(null);
+parsePreferHeader(undefined);