So the main issue is that our DataFetcher returns the data using the alias names ("result key" technically), not the field definition. This makes it possible to use each field many times with different aliases and different arguments. But since the PropertyDataFetcher only has access to the field name, not the query alias, it looks up the wrong thing from the source. That is essentially the issue.

For now I have worked around this issue by overloading getFieldDef in ExecutionStrategy, replacing field name with alias when appropriate. Works, but it's definitely a hack though.

Let me give some more context. We convert each top-level GraphQL query field to a single Neo4j Cypher database query. So, if a field is used many times at the same level for the same object we need some way to distinguish them in the Cypher query. I thought result key seemed like the natural choice, but from your comment it almost sounds like I need to use field+arguments as key instead, e.g. "aggregate_median_salary", where aggregate is field name and the other two are argument values. Am I understanding this correctly?

I dont know about Neo4j Cypher database query at all but a field be called with different argument values ONLY if it has an alias. So yes the field name and arguments are kinda uniqueness keys

I would be more than happy to use a custom DataFetcher but as far as I can tell the DataFetcherFactory does not get access to the alias upon instantiation, hence the hack to replace the field definition name with the alias. If the factory got the alias as input, then yes, I would just do that, done deal.

I tried your suggestion and created a custom DataFetcher, and yes, that did the trick. Basically all I had to do was this:

                    @Override
                    public Object get(DataFetchingEnvironment environment) throws Exception {
                        if (environment.getSource() instanceof Map<?,?> resultMap)
                        {
                            return resultMap.get(environment.getField().getResultKey());
                        } else
                        {
                            throw new IllegalArgumentException("Don't know how to get the value");
                        }
                    }

and that was enough!

Thanks for your assistance, much appreciated.

Glad you have it working

Just note that resultMap.get(environment.getField().getResultKey()) means you are allowing the client to "control" what data comes back from your system.

Now with a map of values - maybe thats ok - very low - but the client is in control not the server.

https://xkcd.com/327/