Fixes issue affecting the auth providers (#3211)

* Reproduces error for issue 3208

* Make sure we don't override a default adapter with the options when validation function are not provided

src/Adapters/Auth/index.js

@@ -55,6 +55,36 @@ function authDataValidator(adapter, appIds, options) {
   }
 }
 
+function loadAuthAdapter(provider, authOptions) {
+  const defaultAdapter = providers[provider];
+  const adapter = Object.assign({}, defaultAdapter);
+  const providerOptions = authOptions[provider];
+
+  if (!defaultAdapter && !providerOptions) {
+    return;
+  }
+
+  const appIds = providerOptions ? providerOptions.appIds : undefined;
+
+  // Try the configuration methods
+  if (providerOptions) {
+    const optionalAdapter = loadAdapter(providerOptions, undefined, providerOptions);
+    if (optionalAdapter) {
+      ['validateAuthData', 'validateAppId'].forEach((key) => {
+        if (optionalAdapter[key]) {
+          adapter[key] = optionalAdapter[key];
+        }
+      });
+    }
+  }
+
+  if (!adapter.validateAuthData || !adapter.validateAppId) {
+    return;
+  }
+
+  return {adapter, appIds, providerOptions};
+}
+
 module.exports = function(authOptions = {}, enableAnonymousUsers = true) {
   let _enableAnonymousUsers = enableAnonymousUsers;
   const setEnableAnonymousUsers = function(enable) {
@@ -67,33 +97,19 @@ module.exports = function(authOptions = {}, enableAnonymousUsers = true) {
       return;
     }
 
-    const defaultAdapter = providers[provider];
-    let adapter = defaultAdapter;
-    const providerOptions = authOptions[provider];
-
-    if (!defaultAdapter && !providerOptions) {
-      return;
-    }
-
-    const appIds = providerOptions ? providerOptions.appIds : undefined;
-
-    // Try the configuration methods
-    if (providerOptions) {
-      const optionalAdapter = loadAdapter(providerOptions, undefined, providerOptions);
-      if (optionalAdapter) {
-        adapter = optionalAdapter;
-      }
-    }
-
-    if (!adapter.validateAuthData || !adapter.validateAppId) {
-      return;
-    }
+    const {
+      adapter,
+      appIds,
+      providerOptions
+    } = loadAuthAdapter(provider, authOptions);
 
     return authDataValidator(adapter, appIds, providerOptions);
   }
 
   return Object.freeze({
     getValidatorForProvider,
-    setEnableAnonymousUsers,
+    setEnableAnonymousUsers
   })
 }
+
+module.exports.loadAuthAdapter = loadAuthAdapter;