Struct tests are failing in IonHashTest.ion

[byronlin13]

Scenarios:

ion:{$0:1}
ion:{               
    'null':null,
    bool:false,
    int:5,
    neg_int:-6,
    float:4.9e-324,
    decimal:123.45,
    timestamp:2017-01-01T00:00:00-00:00,
    symbol:hello,
    string:"hello",
    clob:{{"hello"}},
    blob:{{aGVsbG8=}},
    list:[1,2,3],
    sexp:(1 2 3),
    struct:{},
    annotated_value:hello::{},
}

[byronlin13]

scenario: {$0:1} is failing on IonHashWriterTest.cs and returning System.InvalidOperationException: In a struct but field name is not set exception.

The test creates a reader that reads the struct and is passed into writer.writeValues(). As the reader moves next to $0 symbol, the CurrentFieldName is called but is not written to the writer because it is null. When the writer tries to write 1, the field name is not set and the exception is thrown.

The fix is to call SetFieldNameSymbol() instead of SetFieldName() so the zero symbol is set to the writer.

https://github.com/amzn/ion-hash-dotnet/blob/master/Amazon.IonHashDotnet/IonHashWriter.cs#L262-L266

[byronlin13]

The zero symbol struct scenario: {$0:1} has been resolved by PR: #21