This edition of rare and silly errors is brought to you by LINQ:
_16Exception: System.ArgumentException
_16Message: nodes cannot be empty.
_16Source: Sitecore.ContentSearch.Linq
_16 at Sitecore.ContentSearch.Linq.Nodes.OrNode..ctor(QueryNode[] nodes)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitNonItemTypeEnumerableContainsMethod(MethodCallExpression methodCall, ConstantNode left, QueryNode right)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitBinary(BinaryExpression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitBinary(BinaryExpression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitBinary(BinaryExpression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitBinary(BinaryExpression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.VisitWhereMethod(MethodCallExpression methodCall)
_16 at Sitecore.ContentSearch.Linq.Parsing.ExpressionParser.Parse(Expression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.GenericQueryable`2.GetQuery(Expression expression)
_16 at Sitecore.ContentSearch.Linq.Parsing.GenericQueryable`2.GetEnumerator()
_16 at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
_16 at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
The offending line was where Sitecore ContentSearch's GetQueryable was called:
_7using (var searchContext = QueryHelper.SearchIndex.CreateSearchContext())
_7 var results = searchContext
_7 .GetQueryable<MySearchResultItem>()
Knowing that the problem wasn't actually there, I inspected the query that was built prior to calling GetQueryable:
_5var query = PredicateBuilder.True<MySearchResultItem>();
_5ID[] legacyTargets = GetLegacyItemTargets();
_5query = query.And(x => legacyTargets.Contains(x.ItemId));
Given that the error message said nodes are empty, the smoking gun was the "array contains x" operation.
But it worked on all environments, except for one! Turns out, it's because the legacyTargets array WAS empty.
This was due to a content delta between environments in which some items that were expected to be there... Weren't.
This situation is such a classic one in Sitecore. When fetching any information related to items, there will always be a chance that information is missing or different than you were expecting. Defensive programming pays dividends.
Keep on building,
Marcel
