MultiGet ignores _source field (reopen #849)

[lakario]

Issue #849 reported that MultiGet was ignoring _source fields. The issue has since been closed with a supposed fix pushed to develop. Having tested that fix, I can confirm that functionality is still missing.

Here's a sample which demonstrates the issue (references latest develop sources):

class Program
{
    static void Main(string[] args)
    {
        const string serverUrl = "http://localhost:9200";
        const string indexName = "test";
        const bool resetAll = false;

        var guids = new[] {
            new Guid("16b006aa-416f-42e4-801c-7f61f6d74294"),
            new Guid("eb2e4f76-a697-4690-b339-cf923eda2c92"),
            new Guid("494d59fa-965d-4c84-96e3-ac617a7536ca"),
        };

        var client = new ElasticClient(new ConnectionSettings(new Uri(serverUrl))
            .SetTimeout(15000)
            .SetDefaultIndex(indexName));

        if (resetAll || !client.IndexExists(x => x.Index(indexName)).Exists)
        {
            ResetIndex(client, indexName, guids);
        }

        var response = client.MultiGet(s => s
            .GetMany<Thing>(guids.Select(x => x.ToString()))
            .SourceInclude<Thing>(x => x.Id, x => x.Name));

        DisplayThings(response.Documents.Select(x => x.Source).Cast<Thing>());

        Console.ReadKey();
    }

    static void DisplayThings(IEnumerable<Thing> things)
    {
        foreach (var item in things)
        {
            Console.WriteLine("{1}{0}{1}{1}{2}", item, Environment.NewLine, new String('*', 50));
        }
    } 

    static void ResetIndex(IElasticClient client, string indexName, IList<Guid> guids)
    {
        Action fnCreate = () =>
        {
            client.CreateIndex(x => x.Index(indexName));
            client.Map<Thing>(x => x.MapFromAttributes());
        };

        if (client.IndexExists(x => x.Index(indexName)).Exists)
        {
            client.DeleteIndex(x => x.Index(indexName));
            fnCreate();
        }
        else
        {
            fnCreate();
        }

        var items = new[] {
            new Thing() {
                Id = guids[0],
                Name = "Thing 1",
                Description = "This is a description for thing 1"
            },
            new Thing() {
                Id = guids[1],
                Name = "Thing 2",
                Description = "This is a description for thing 2"
            },
            new Thing() {
                Id = guids[2],
                Name = "Thing 3",
                Description = "This is a description for thing 3"
            },
        };

        client.IndexMany(items);
    }

    [ElasticType(IdProperty = "Id", Name = "thing")]
    public class Thing
    {
        public Guid Id { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }

        public override string ToString()
        {
            return String.Format("Id: {0}{3}" +
                                 "Name: {1}{3}" +
                                 "Description: {2}",
                                 Name, Id, Description ?? "<null>", Environment.NewLine);
        }
    }
}   

[gmarz]

@lakario Yup, I just confirmed this as well. I'm looking into it, thanks for following up.

[Mpdreamz]

Yeah huge props for the code to reproduce the issue 👍, we should have confirmed that we saw your comment on #849 quicker :)

[lakario]

Thanks guys. I wasn't sure if notifications stopped on closed issues so I opened a new one just in case.

[gmarz]

@Mpdreamz so I think the issue here lies in ApiGenerator, where we are explicitly renaming the source query params from the REST spec.

var globalQueryStringRenames = new Dictionary<string, string>
{
    {"_source", "source_enabled"},
    {"_source_include", "source_include"},
    {"_source_exclude", "source_exclude"},
};

I'm not sure of the nature or history of why we're doing this, but it's causing the API calls to be incorrect.

[Mpdreamz]

That bit is to be able to override the generated C# method names.

There was a bug though that caused them to send the wrong querystring params that I though I fixed in this commit:

1cd084e

[gmarz]

Ah, I see. The problem is actually with the RequestParametersExtensions generated class still using the wrong param names. If you use the methods that take params string[] you're fine, but if you use the overloaded methods that take expressions then you'll run into this bug.

[gmarz]

Pushed the above fix. @lakario feel free to get latest and confirm. Thanks again for reporting.

[lakario]

Fix looks good. Thanks guys.

[lakario]

Just verified locally under the exact same conditions as originally.

New issue opened: #1235.