express-session: fix Store#get callback parameter type (#23240)

The type of the second parameter of Store#get should be SessionData,
not Session. It's bit confusing because parameter name "session" is
used for both Session and SessionData on their documentation.

types/express-session/express-session-tests.ts

@@ -37,3 +37,34 @@ app.use((req, res, next) => {
     res.end('welcome to the session demo. refresh!');
   }
 });
+
+// Custom Session Store
+
+class MyStore extends session.Store {
+  private sessions: { [sid: string]: string };
+
+  constructor() {
+    super();
+    this.sessions = {};
+  }
+
+  get = (sid: string, callback: (err: any, session: Express.SessionData) => void): void => {
+    callback(null, JSON.parse(this.sessions[sid]));
+  }
+
+  set = (sid: string, session: Express.Session, callback: (err: any) => void): void => {
+    this.sessions[sid] = JSON.stringify(session);
+    callback(null);
+  }
+
+  destroy = (sid: string, callback: (err: any) => void): void => {
+    this.sessions[sid] = undefined;
+    this.sessions = JSON.parse(JSON.stringify(this.sessions));
+    callback(null);
+  }
+}
+
+app.use(session({
+  secret: 'keyboard cat',
+  store: new MyStore()
+}));

types/express-session/index.d.ts

@@ -1,6 +1,6 @@
 // Type definitions for express-session 1.15
 // Project: https://www.npmjs.org/package/express-session
-// Definitions by: Hiroki Horiuchi <https://github.com/horiuchi>, Jacob Bogers <https://github.com/jacobbogers>
+// Definitions by: Hiroki Horiuchi <https://github.com/horiuchi>, Jacob Bogers <https://github.com/jacobbogers>, Naoto Yokoyama <https://github.com/builtinnya>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
@@ -64,7 +64,7 @@ declare namespace session {
   }
 
   interface BaseMemoryStore {
-    get: (sid: string, callback: (err: any, session: Express.Session) => void) => void;
+    get: (sid: string, callback: (err: any, session: Express.SessionData) => void) => void;
     set: (sid: string, session: Express.Session, callback: (err: any) => void) => void;
     destroy: (sid: string, callback: (err: any) => void) => void;
     length?: (callback: (err: any, length: number) => void) => void;
@@ -78,7 +78,7 @@ declare namespace session {
     load: (sid: string, fn: (err: any, session: Express.Session) => any) => void;
     createSession: (req: express.Request, sess: Express.SessionData) => void;
 
-    get: (sid: string, callback: (err: any, session: Express.Session) => void) => void;
+    get: (sid: string, callback: (err: any, session: Express.SessionData) => void) => void;
     set: (sid: string, session: Express.Session, callback: (err: any) => void) => void;
     destroy: (sid: string, callback: (err: any) => void) => void;
     all: (callback: (err: any, obj: { [sid: string]: Express.SessionData; }) => void) => void;
@@ -87,7 +87,7 @@ declare namespace session {
   }
 
   class MemoryStore implements BaseMemoryStore {
-    get: (sid: string, callback: (err: any, session: Express.Session) => void) => void;
+    get: (sid: string, callback: (err: any, session: Express.SessionData) => void) => void;
     set: (sid: string, session: Express.Session, callback: (err: any) => void) => void;
     destroy: (sid: string, callback: (err: any) => void) => void;
     all: (callback: (err: any, obj: { [sid: string]: Express.Session; }) => void) => void;