Anchored DateMath no longer serializes time zone information for local DateTime

[jonyadamit]

NEST/Elasticsearch.Net version:
7.0.0
Elasticsearch version:
7.2.0
Description of the problem including expected versus actual behavior:
Given the query

var result = client.Search<object>(s => s
                .Index("test")
                .Query(q => q
                    .DateRange(dr => dr
                        .GreaterThanOrEquals(DateTime.Now)
                        .Field("some_field"))));

Nest 6.8.0 generates the following query: (my local time is UTC + 3)
{"query":{"range":{"some_field":{"gte":"2019-07-01T17:16:18.1266967+03:00"}}}}

Nest 7.0.0 generates the following query:
{"query":{"range":{"some_field":{"gte":"2019-07-01T17:16:18.1266967"}}}}

As a workaround for now I guess I have to either manually convert dates to UTC or add the TimeZone property (either of which adds unnecessary complexity).

[russcam]

Thanks for opening @jonyadamit. This is a bug that has crept in with the move to Utf8Json. Will open a fix shortly.

In the meantime, the workaround would be to convert the DateTime instance to a date string in your application, and pass this string to .GreaterThanOrEquals(...)

[russcam]

I've opened #3910 to address

[bkqc]

This is only a suggestion but wouldn't it be cleaner in the DateMath.ToMinThreeDecimalPlaces function to simply change the actual "yyyy-MM-ddTHH:mm:ss.FFFFFFF" format to "yyyy-MM-ddTHH:mm:ss.fffffffK" or we we really need to keep the string shorter, get the timezone string in a second call to .ToString(" K").Substring(1) and concatenate instead of reimplementing the TZ logic?