Api to unlink a provider

Author: vratojr

docs/AUTHENTICATION.md

@@ -639,6 +639,17 @@ Shouldn't be more complicated than:
 ```
 </details>
 
+### unlinking provider
+For a given user, and a given provider ("google.com","password",...)
+
+<details>
+ <summary>Native API</summary>
+
+```js
+  user.unlink(providerId);
+```
+</details>
+
 ### reauthenticate
 Some security-sensitive actions (deleting an account, changing a password) require that the user has recently signed in.
 If you perform one of these actions, and the user signed in too long ago, the action fails.

src/firebase.android.ts

@@ -663,6 +663,30 @@ firebase.logout = arg => {
   });
 };
 
+firebase.unlink = providerId => {
+  return new Promise((resolve, reject) => {
+    try {
+      const user = com.google.firebase.auth.FirebaseAuth.getInstance().getCurrentUser();
+      if (!user) {
+        resolve();
+      }
+      user.unlink(providerId).addOnCompleteListener(new com.google.android.gms.tasks.OnCompleteListener({
+        onComplete: task => {
+          if (task.isSuccessful()) {
+            resolve();
+          } else {
+            reject((task.getException() && task.getException().getReason ? task.getException().getReason() : task.getException()));
+          }
+        }
+      })
+      );
+    } catch (ex) {
+      console.log("Error in firebase.unlink: " + ex);
+      reject(ex);
+    }
+  });
+};
+
 firebase.getAuthToken = arg => {
   return new Promise((resolve, reject) => {
     try {

src/firebase.ios.ts

@@ -590,6 +590,26 @@ firebase.logout = arg => {
   });
 };
 
+firebase.unlink = providerId => {
+  return new Promise((resolve, reject) => {
+    try {
+      const user = FIRAuth.auth().currentUser;
+
+      user.unlinkFromProviderCompletion(providerId, (user, error) => {
+        if (error) {
+          reject(error.localizedDescription);
+        } else {
+          resolve(user);
+        }
+      });
+
+    } catch (ex) {
+      console.log("Error in firebase.logout: " + ex);
+      reject(ex);
+    }
+  });
+};
+
 function toLoginResult(user, additionalUserInfo?: FIRAdditionalUserInfo): User {
   if (!user) {
     return null;