Bug 1633344 - Throw RangeError when creating PaymentRequest with a duplicate payment method. r=alchen

Differential Revision: https://phabricator.services.mozilla.com/D74686

dom/payments/PaymentRequest.cpp

@@ -305,6 +305,7 @@ void PaymentRequest::IsValidMethodData(
     return;
   }
 
+  nsTArray<nsString> methods;
   for (const PaymentMethodData& methodData : aMethodData) {
     IsValidPaymentMethodIdentifier(methodData.mSupportedMethods, aRv);
     if (aRv.Failed()) {
@@ -325,6 +326,13 @@ void PaymentRequest::IsValidMethodData(
         return;
       }
     }
+    if (!methods.Contains(methodData.mSupportedMethods)) {
+      methods.AppendElement(methodData.mSupportedMethods);
+    } else {
+      aRv.ThrowRangeError(nsPrintfCString(
+          "Duplicate payment method '%s'",
+          NS_ConvertUTF16toUTF8(methodData.mSupportedMethods).get()));
+    }
   }
 }