Executing multiple lookup gets with different types fails

I am wondering if you can help with an issue I am facing regarding SubDoc LookupIn chaining as I am getting a ClientFailure and looking at the Exception message it is nable to cast object of type 'System.Collections.Generic.List`1[Couchbase.Core.IO.SubDocument.OperationSpec]' to type 'My Document POCO Type'

var lookupBuilder = bucket.LookupIn<T>(identifier);

lookupBuilder.Get(lookup.Path1).Get(lookup.Path2)

var documentFragmentResult = await lookupBuilder.ExecuteAsync();

this is failing, however if I do not chain the Get() and only do one Get() it works

what am i doing wrong?

Jeffry Morris @jeffrymorris Dec 27 2019 22:42

@mfeerick sounds like a bug. What is the SDK version you are using?

mfeerick @mfeerick Jan 06 08:52

@jeffrymorris I am using 2.7.15 which afaik is the latest.

mfeerick @mfeerick Jan 06 10:53

couchbase-net-client/src/Couchbase/IO/Operations/SubDocument/MultiLookup.cs:line 115

return (T)_lookupCommands;

Mike Goldsmith @MikeGoldsmith Jan 06 13:13

Hi @mfeerick - just FYI @jeffrymorris is based on West coast so won’t be available to respond for a little while.

Can you give some context to the cs file & line number you pointed out?

mfeerick @mfeerick Jan 06 14:25

@MikeGoldsmith This is where an exception is thrown when attempting to do a MultiLookup

var lookupBuilder = bucket.LookupIn<T>(identifier);

lookupBuilder.Get(lookup.Path1).Get(lookup.Path2)

var documentFragmentResult = await lookupBuilder.ExecuteAsync();

Mike Goldsmith @MikeGoldsmith Jan 06 15:35

Please can you provide a full example with both code and JSON document you’re using that generates the error?

mfeerick @mfeerick Jan 07 22:33

@MikeGoldsmith sure ive created a simple example at: https://dotnetfiddle.net/lsLpqH

The result of the lookupBuilder.Execute() will be a "ClientFailure"

My debugging the CouchbaseNetClient source shows the issue on line 115 of couchbase-net-client/src/Couchbase/IO/Operations/SubDocument/MultiLookup.cs

mfeerick @mfeerick Jan 07 22:40

where it is attempting to cast a List<Couchbase.Core.IO.SubDocument.OperationSpec> to a <T> so in my example a "Test"

I also figured out why it works if you dont chain multiple Gets, and that is because it runs different code.

@jeffrymorris @MikeGoldsmith I have fixed this issue in MultiLookup.cs with a small change, do you accept pull requests on github?