NullReferenceException when Deserializing with null PropertyNamingPolicy option

[cedemax]

Deserializing a complex object (I could not replicate the error with a dummy object) with a null PropertyNamingPolicy throws NullReferenceException.

My code :

var a = JsonSerializer.Deserialize<T>(jsonString,options);  // options.PropertyNamingPolicy = null

Stack trace:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=System.Text.Json
  StackTrace:
   at System.Text.Json.JsonPropertyInfo.Read(JsonTokenType tokenType, ReadStack& state, Utf8JsonReader& reader) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonPropertyInfo.cs:line 345
   at System.Text.Json.JsonSerializer.HandleValue(JsonTokenType tokenType, JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& state) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.HandleValue.cs:line 28
   at System.Text.Json.JsonSerializer.ReadCore(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& readStack) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.cs:line 50
   at System.Text.Json.JsonSerializer.ReadCore(Type returnType, JsonSerializerOptions options, Utf8JsonReader& reader) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.Helpers.cs:line 22
   at System.Text.Json.JsonSerializer.ParseCore(String json, Type returnType, JsonSerializerOptions options) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.String.cs:line 73
   at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, JsonSerializerOptions options) in /_/src/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.String.cs:line 28

The jsonString

{"General":{"InnerRegionMode":"Hole"},"File":{"Format":"svg","PreferZip":false,"PreferOneFile":false,"SupportedFormats":[["svg"]]},"Coordinates":{"System":{"Projection":{"Name":"ETRS-TM35FIN"},"Scale":1000.0,"Origin":{"X":0.0,"Y":0.0,"Z":0.0},"Unit":{"UnitOf":2,"Name":"millimetre","Scale":0.001,"Symbol":"mm"}},"Flatten":false,"Centering":false,"Grids":null,"OneMetre":1.0,"OneMillimetre":0.001,"OneCentimetre":0.01},"Terrain":{"Exaggerate":2.5,"Contours":{"Closed":true,"Delta":0.5,"Reduce":0.1,"Smooth":0.0,"MinArea":9.0,"Highlights":{"N":10,"OutlineColor":"rgba(0,0,0,0.54)","FillColor":null,"StrokeWidth":0.9,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Labels":1,"LabelSpacing":50.0,"IndividualLayers":false,"OutlineColor":"rgba(0,0,0,0.29)","FillColor":null,"StrokeWidth":0.5,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Mesh":null,"Compression":{"InnerDensity":1.0,"OuterDensity":1.0,"DensityProfile":"Flat","InnerRegionTemplateId":null,"Enabled":false,"Layer":null,"Flatten":false,"ClipMode":0},"Texture":{"Colors":["rgba(69,114,45,1)","rgba(144,160,110,1)","rgba(195,160,105,1)","rgba(243,243,243,1)"],"ColorMap":{"Colors":["69, 114, 45","144, 160, 110","195, 160, 105","243, 243, 243"],"WaterColor":"","Contrast":0.0,"Min":0.0,"Max":1.0,"IsClear":false},"FlatColor":"DarkGray","Style":"ColorMap","SupportedStyles":null,"Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"CellLimit":0.0,"Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Shores":{"GuessDepth":false,"OutlineColor":"rgba(0,100,200,0.59)","FillColor":"rgba(66,164,194,0.48)","StrokeWidth":1.0,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Roads":{"DefaultWidth":3.0,"ExtraWidth":0.0,"OutlineColor":"rgba(53,51,51,0.92)","FillColor":"rgba(184,167,167,1)","StrokeWidth":1.0,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Buildings":{"GuessHeight":false,"ManualHeight":0.0,"ShowID":false,"OutlineColor":"rgba(0,0,0,1)","FillColor":"rgba(138,138,138,1)","StrokeWidth":1.0,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Properties":{"Text":{"ProportionalSize":true,"MinSize":1.0,"MaxSize":50.0,"OutlineColor":"rgba(0,0,0,1)","FillColor":"rgba(255,255,255,1)","StrokeWidth":4.0,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0},"Markers":{"ShowAccuracyBounds":true,"ShowID":false,"OutlineColor":"rgba(255,0,255,1)","FillColor":null,"StrokeWidth":0.3,"DataStyle":"Outline2D","Enabled":false,"Layer":null,"Flatten":false,"ClipMode":0},"OutlineColor":"rgba(132,35,221,0.79)","FillColor":null,"StrokeWidth":1.0,"DataStyle":"Outline2D","Enabled":true,"Layer":null,"Flatten":false,"ClipMode":0}}

The type it maps to has a lot of code so I won't be posting it here. The deserialization 'works', but everything is null after deserialization when using JsonNamingPolicy.CamelCase.
If using PropertyNameCaseInsensitive = true and JsonNamingPolicy.CamelCase then it will again throw NullReferenceException on the same line as before...

EDIT:

This seemed to be caused by having a custom JsonConverter<System.Drawing.Color?>, but no JsonConverter<System.Drawing.Color> defined... The complex class contained both Color and Color? objects. Adding the non-nullable version fixed the issue. The error was quite unhelpful however.

[steveharter]

This seemed to be caused by having a custom JsonConverter<System.Drawing.Color?>, but no JsonConverter<System.Drawing.Color> defined.

You only need to define a custom converter for the non-nullable type. Nullable is handled automatically.

However, the NullReferenceException is a bug and should be fixed. Thanks for creating the issue.

[buyaa-n]

Seems this one fixed with https://github.com/dotnet/corefx/pull/40501/files

[layomia]

Can't repro this. #32006 added logic to use a compatible JsonConverter for a type T? when specified with [JsonConverter]. Please reopen if you still face issues here.