Directly initialize properties in UserMetadata

src/auth/user-record.ts

@@ -66,16 +66,19 @@ export interface CreateRequest extends UpdateRequest {
  * @constructor
  */
 export class UserMetadata {
-  public readonly creationTime: string;
-  public readonly lastSignInTime: string;
+  public readonly creationTime?: string | null;
+  public readonly lastSignInTime?: string | null;
 
   constructor(response: any) {
     // Creation date should always be available but due to some backend bugs there
     // were cases in the past where users did not have creation date properly set.
     // This included legacy Firebase migrating project users and some anonymous users.
     // These bugs have already been addressed since then.
-    utils.addReadonlyGetter(this, 'creationTime', parseDate(response.createdAt));
-    utils.addReadonlyGetter(this, 'lastSignInTime', parseDate(response.lastLoginAt));
+    this.creationTime = parseDate(response.createdAt);
+    utils.enforceReadonly(this, 'creationTime');
+
+    this.lastSignInTime = parseDate(response.lastLoginAt);
+    utils.enforceReadonly(this, 'lastSignInTime');
   }
 
   /** @return {object} The plain object representation of the user's metadata. */

src/index.d.ts

@@ -491,13 +491,12 @@ declare namespace admin.auth {
     /**
      * The date the user last signed in, formatted as a UTC string.
      */
-    lastSignInTime: string;
+    lastSignInTime?: string | null;
 
     /**
      * The date the user was created, formatted as a UTC string.
-     *
      */
-    creationTime: string;
+    creationTime?: string | null;
 
     /**
      * @return A JSON-serializable representation of this object.

src/utils/index.ts

@@ -55,6 +55,20 @@ export function addReadonlyGetter(obj: object, prop: string, value: any): void {
   });
 }
 
+/**
+ * Marks an existing property as readonly. Unlike typescript's "readonly"
+ * modifier, this will take effect at runtime too (generating a TypeError if
+ * violated), including when called from javascript.
+ */
+export function enforceReadonly(obj: object, prop: string): void {
+  Object.defineProperty(obj, prop, {
+    // Make this property read-only.
+    writable: false,
+    // Include this property during enumeration of obj's properties.
+    enumerable: true,
+  });
+}
+
 /**
  * Returns the Google Cloud project ID associated with a Firebase app, if it's explicitly
  * specified in either the Firebase app options, credentials or the local environment.