Apex class that returns a handled error for Lightning Components

daraDisplayComponent.cmp

<aura:component controller="FetchDataApexController" implements="force:lightningQuickActionWithoutHeader,force:appHostable,flexipage:availableForAllPageTypes,force:hasRecordId" extends="c:dataFetch" access="global">

	<aura:handler name="loading" event="c:loading" action="{!c.spinnerShow}" />
	<aura:handler name="doneloading" event="c:done_loading" action="{!c.spinnerHide}" />
	<aura:handler name="init" value="{!this}" action="{!c.doInit}" />
	<aura:attribute name="queryList" type="Object[]" default="[]" />
  
	<aura:dependency resource="c:Modal_Dialog" />
	
	<div class="slds">

		<div aura:id="optionalModalDialog" />
		
	</div>
</aura:component>

dataDisplayController.js

({

	getHistoryFunction : function(component, event, helper) {
		var selectedAccts = component.get("v.queryList");
		var params = {
			"acct" : selectedAccts,
		};

		helper.callServer(component, "c.getDataFromServer", function(response) {
			// console.log('response ' + response);
			if (!response[0].message && !response.includes('No records')) {
				// Process data here if the response does not return an error or
				// contain 0 records

			} else {

				// otherwise display the message (no records returned) if exists
				var msg = response[0].message;

				if (msg) {
					helper.alert(component, 'Error Fetching Data', msg);
				} else {
					// Or display the handled error returned from the server
					helper.alert(component, 'Error Fetching Data', response);
				}

			}
		}, params);

	}

})

dataDisplayHelper.js

{(
  
alert : function(component, title, message) {
		$A.createComponent("c:Modal_Dialog", {
			"title" : title,
			"body" : message,
			"cancelLabel" : "",
			"onclose" : component.getReference("c.onDestroyModalDialog"),
			"oncancel" : component.getReference("c.onDestroyModalDialog"),
			"onconfirm" : component.getReference("c.onDestroyModalDialog")
		}, function(msgBox) {
			// Add the new button to the body array
			if (component.isValid()) {
				var targetCmp = component.find('optionalModalDialog');
				var body = targetCmp.get("v.body");
				body.push(msgBox);
				targetCmp.set("v.body", body);
			}
		});

	}
 
})

dataFetch.cmp

<aura:component abstract="true" access="global">
    <aura:registerEvent name="loading" type="c:loading"/>
    <aura:registerEvent name="doneloading" type="c:done_loading"/>
	{!v.body}
</aura:component>

dataFetchHelper.js

({
    callServer : function(component,method,callback,params) {
        var compEvent = component.getEvent("loading");
        compEvent.fire();
        
        var action = component.get(method);
        if (params) {
            action.setParams(params);
        }
        
        action.setCallback(this,function(response) {
            var state = response.getState();
            console.log('response ' + state);
            var values = response.getReturnValue();
            //console.log('response keys ' + Object.keys(response));
            //console.log('response values ' + Object.values(response))
            if (state === "SUCCESS" && values.length != 0) { 
                
                callback.call(this,response.getReturnValue());   
                
            }
            if (state === "ERROR") {
                // generic error handler
                var errors = response.getError();
                if (errors) {
                    callback.call(this,errors);
                    console.log("Errors", errors);
                    compEvent = component.getEvent("doneloading");
                    compEvent.fire();
                }
            }
            else if(values.length == 0){
                callback.call(this,'No records returned from query');
                compEvent = component.getEvent("doneloading");
                compEvent.fire();
            }
            compEvent = component.getEvent("doneloading");
            compEvent.fire();
        });
        
        $A.enqueueAction(action);
    }
})

FetchDataApexController.cls

public with sharing class FetchDataApexController {
    
    @AuraEnabled
			public static List<sObject> getDataFromServer(List<String> acct){
        List<sObject> sObjList = new List<sObject>();
        
        String query = 'SELECT ';
				query = query + 'Name, Id, customField__c FROM customObject__c ';
				query = query + 'WHERE Id IN: acct ';
        query = query + ' ORDER BY CreatedOn__c DESC';
        
        system.debug('query string ' + query);
        
        try{
							
            if(!test.isRunningTest()){
            	sObjList = Database.query(query);
            }

        }
        catch(system.Exception ex){
            system.debug('error ' + ex.getCause());
             throw new AuraHandledException('Something went wrong while fetching your records. '+
             'This is the error message produded by the system: '+ ex.getMessage());
            
            
        }
        return sObjList;

    }
    
    
}

This is not a fully implementable example but is intended to show how to pass handled errors from Apex to Lightning... see my blog post for more