sObject array parameter in Lightning causes Internal Salesforce.com Error in Apex controller

The problem is deep inside of the transport/marshalling interface layer between Lightning Components and Apex and will need to be fixed by my team.

For now I have developed a generic workaround using a small amount of Apex.

public class OneLeadController {

    @AuraEnabled
    public static Id createLead(Lead newLead) {
        insert newLead;
        return newLead.Id;
    }

    @AuraEnabled
    public static List<Id> createLeads(String newLeads) {
        List<SObject> newSObjectsList = convertJSONToListOfSObject(newLeads);

        insert newSObjectsList;

        List<Id> newIds = new List<Id>();
        for (SObject o : newSObjectsList) {
            newIds.add(o.Id);
        }

        return newIds;
    }

    @AuraEnabled
    public static Lead newLead() {
        return (Lead)Lead.sObjectType.newSObject(null, true);
    }

    private static List<SObject> convertJSONToListOfSObject(String json) {
        Object[] values = (Object[])System.JSON.deserializeUntyped(json);

        List<SObject> newSObjectsList = new List<SObject>();
        for (Object v : values) {
            Map<String, Object> m = (Map<String, Object>)v;

            Schema.SObjectType targetType = Schema.getGlobalDescribe().get((String)m.get('sobjectType'));

            SObject o = targetType.newSObject();

            Map<String, Schema.SObjectField> fields = targetType.getDescribe().fields.getMap();
            for (String fieldName : m.keySet()) {
                // Filter out any psuedo fields such as LastNameLocal
                Schema.SObjectField fi = fields.get(fieldName);
                if (fi != null) {
                    if (fi.getDescribe().isCreateable() && fi.getDescribe().isUpdateable()) {
                        o.put(fieldName, m.get(fieldName)); 
                    }
                }
            }

            newSObjectsList.add(o);
        }

        return newSObjectsList;
    }
}

and a small corresponding change to the client side controller (oneLeadController.js) calling this:

({
    save : function(component, event, helper) {
        var self = this;

        var createLeads = component.get("c.createLeads");
        createLeads.setParams({
            "newLeads": $A.util.json.encode(component.get("v.leads"))
        });

        createLeads.setCallback(self, function(a) {
            if (a.getState() === "SUCCESS") {
                console.log("returned: %o", a.getReturnValue());
            } else {
                alert($A.util.json.encode(a.getError()));
            }
        })

        $A.enqueueAction(createLeads);
    }
})