fix: Deserialize parseable POCO properties to the nullable underlying type (influxdata#251)

Author: vesuvian

CHANGELOG.md

@@ -3,7 +3,7 @@
 ### Features
 1. [#239](https://github.com/influxdata/influxdb-client-csharp/pull/239): Add support for Asynchronous queries [LINQ]
 1. [#240](https://github.com/influxdata/influxdb-client-csharp/pull/240): Add IsMeasurement option to Column attribute for dynamic measurement names in POCO classes
-1. [#246](https://github.com/influxdata/influxdb-client-csharp/pull/246): Add support for deserialization of POCO column property types with a "Parse" method, such as Guid
+1. [#246](https://github.com/influxdata/influxdb-client-csharp/pull/246), [#251](https://github.com/influxdata/influxdb-client-csharp/pull/251): Add support for deserialization of POCO column property types with a "Parse" method, such as Guid
 
 ## 3.0.0 [2021-09-17]
 

Client.Core/Flux/Internal/FluxResultMapper.cs

@@ -153,8 +153,12 @@ private void SetFieldValue<T>(T poco, PropertyInfo property, object value)
  return;
  }
 
+ // Nullable types cannot be used in type conversion, but we can use Nullable.GetUnderlyingType()
+ // to determine whether the type is nullable and convert to the underlying type instead
+ var targetType = Nullable.GetUnderlyingType(propertyType) ?? propertyType;
+
  // Handle parseables
- var parseMethod = GetParseMethod(propertyType, valueType);
+ var parseMethod = GetParseMethod(targetType, valueType);
  if (parseMethod != null)
  {
  var parsed = parseMethod.Invoke(null, new[] { value });
@@ -165,9 +169,6 @@ private void SetFieldValue<T>(T poco, PropertyInfo property, object value)
  // Handle convertibles 
  if (value is IConvertible)
  {
- // Nullable types cannot be used in type conversion, but we can use Nullable.GetUnderlyingType()
- // to determine whether the type is nullable and convert to the underlying type instead
- var targetType = Nullable.GetUnderlyingType(propertyType) ?? propertyType;
  property.SetValue(poco, Convert.ChangeType(value, targetType));
  return;
  }
@@ -209,8 +210,10 @@ private MethodInfo GetParseMethod(Type parserType, Type valueType)
  }
 
  var paramType = parameters[0].ParameterType;
- paramType = Nullable.GetUnderlyingType(paramType) ?? paramType;
+ if (valueType == paramType)
+ return true;
 
+ paramType = Nullable.GetUnderlyingType(paramType) ?? paramType;
  return valueType == paramType;
  })
  .FirstOrDefault();

Client.Legacy.Test/FluxResultMapperTest.cs

@@ -118,6 +118,26 @@ public void ParseableProperty()
  Assert.AreEqual(expectedValue, poco.Value);
  Assert.AreEqual(expectedTime, Instant.FromDateTimeUtc(poco.Timestamp));
  }
+ 
+ [TestCase(null)]
+ [TestCase("e11351a6-62ec-468b-8b64-e1414aca2c7d")]
+ public void NullableParseableProperty(string guid)
+ {
+ string expectedTag = "test";
+ Guid? expectedValue = guid == null ? (Guid?)null : Guid.Parse(guid);
+ Instant expectedTime = Instant.FromDateTimeUtc(DateTime.UtcNow);
+
+ var record = new FluxRecord(0);
+ record.Values["tag"] = expectedTag;
+ record.Values["value"] = guid;
+ record.Values["_time"] = expectedTime;
+
+ var poco = _parser.ToPoco<NullableParseablePoco>(record);
+
+ Assert.AreEqual(expectedTag, poco.Tag);
+ Assert.AreEqual(expectedValue, poco.Value);
+ Assert.AreEqual(expectedTime, Instant.FromDateTimeUtc(poco.Timestamp));
+ }
 
  [Measurement("poco")]
  private class ParseablePoco
@@ -131,5 +151,18 @@ private class ParseablePoco
  [Column(IsTimestamp = true)]
  public DateTime Timestamp { get; set; }
  }
+
+ [Measurement("poco")]
+ private class NullableParseablePoco
+ {
+ [Column("tag", IsTag = true)]
+ public string Tag { get; set; }
+
+ [Column("value")]
+ public Guid? Value { get; set; }
+
+ [Column(IsTimestamp = true)]
+ public DateTime Timestamp { get; set; }
+ }
  }
-}
+}