Fix problem in definition when passing a function in the origin: option field. (#27576)

* Fixed type for function passing to cors() origin

If you look at the actual code within @koa/cors and where it invokes any passed function within the origin: option, it invokes it with ctx, the standard Koa context, NOT the Request.  Here is the code fragment..

b5a937fc24/index.js (L58)

Thus changed the signature of the origin option to reflect this.

* Revert back to single quotes -- stupid prettier

Fixed type for function passing to cors() origin

If you look at the actual code within @koa/cors and where it invokes any passed function within the origin: option, it invokes it with ctx, the standard Koa context, NOT the Request.  Here is the code fragment..

b5a937fc24/index.js (L58)

Thus changed the signature of the origin option to reflect this.

types/koa__cors/index.d.ts

@@ -1,10 +1,13 @@
 // Type definitions for @koa/cors 2.2
 // Project: https://github.com/koajs/cors
-// Definitions by: Xavier Stouder <https://github.com/Xstoudi>, Izayoi Ko <https://github.com/izayoiko>, Steve Hipwell <https://github.com/stevehipwell>
+// Definitions by: Xavier Stouder <https://github.com/Xstoudi>
+//                 Izayoi Ko <https://github.com/izayoiko>
+//                 Steve Hipwell <https://github.com/stevehipwell>
+//                 Steven McDowall <https://github.com/sjmcdowall>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
-import * as Koa from "koa";
+import * as Koa from 'koa';
 
 export = cors;
 
@@ -12,7 +15,7 @@ declare function cors(options?: cors.Options): Koa.Middleware;
 
 declare namespace cors {
     interface Options {
-        origin?: ((req: Koa.Request) => string) | string;
+        origin?: ((ctx: Koa.Context) => string) | string;
         allowMethods?: string[] | string;
         exposeHeaders?: string[] | string;
         allowHeaders?: string[] | string;

types/koa__cors/koa__cors-tests.ts

@@ -3,3 +3,11 @@ import cors = require('@koa/cors');
 
 const app = new Koa();
 app.use(cors());
+
+// Trying using cors() passing in a function ..
+function testCorsFunction(ctx: Koa.Context) {
+    const requestOrigin = ctx.request.origin;
+    return requestOrigin;
+}
+
+app.use(cors({ origin: testCorsFunction }));