Avoid null check for User module interface

src/modules/AuthService.ts

@@ -28,25 +28,21 @@ const auth = firebaseApp.auth();
 export function signUp({ email, password }: AuthFormData): Promise<User> {
   return auth
     .createUserWithEmailAndPassword(email, password)
-    .then((UserCredential) => {
-      const { user } = UserCredential;
-      if (user) {
-        return new User(user);
+    .then(({ user }) => {
+      if (user === null) {
+        throw new Error("sign-up failure");
       }
-      throw new Error("User not found");
+      return new User(user);
     });
 }
 
 export function signIn({ email, password }: AuthFormData): Promise<User> {
-  return auth
-    .signInWithEmailAndPassword(email, password)
-    .then((UserCredential) => {
-      const { user } = UserCredential;
-      if (user) {
-        return new User(user);
-      }
-      throw new Error("User not found");
-    });
+  return auth.signInWithEmailAndPassword(email, password).then(({ user }) => {
+    if (user === null) {
+      throw new Error("sign-in failure");
+    }
+    return new User(user);
+  });
 }
 
 export function requestPasswordReset(email: string): Promise<void> {

src/modules/User.ts

@@ -1,10 +1,10 @@
 import firebase from "firebase";
 
-type getToken = Promise<string> | undefined;
+type getToken = Promise<string>;
 
 type IUSER = firebase.User;
 interface Profile {
-  email: string | undefined | null;
+  email: string;
 }
 
 export class User {
@@ -16,12 +16,18 @@ export class User {
 
   // getProfile will return email as of now
   getProfile(): Profile {
+    if (this.user?.email === null) {
+      throw new Error("email not found");
+    }
     return { email: this.user?.email };
   }
   /**
    * Returns a JSON Web Token (JWT) used to identify the user to a Firebase service.
    */
   getToken(): getToken {
-    return this.user?.getIdToken();
+    if (this.user?.getIdToken() === undefined) {
+      throw new Error("token not found");
+    }
+    return this.user.getIdToken();
   }
 }