Preview 8 System.Text.Json error deserializing ObservableCollection

[dweatherman]

Preview 8 System.Text.Json error deserializing ObservableCollection

Example

ObservableCollection<bool> col = new ObservableCollection<bool>();

col.Add(true);
col.Add(false);

string json = System.Text.Json.JsonSerializer.Serialize(col, typeof(ObservableCollection<bool>));
ObservableCollection<bool> result = (ObservableCollection<bool>)System.Text.Json.JsonSerializer.Deserialize(json, typeof(ObservableCollection<bool>));

Result is an exception;

System.Text.Json.JsonException: The JSON value could not be converted to System.Collections.Generic.ICollection`1[System.Boolean]. Path: $ | LineNumber: 0 | BytePositionInLine: 1.
   at System.Text.Json.ThrowHelper.ThrowJsonException(String message, Utf8JsonReader& reader, String path, Exception innerException)
   at System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue(Type propertyType, Utf8JsonReader& reader, String path, Exception innerException)
   at System.Text.Json.ReadStackFrame.CreateEnumerableValue(Utf8JsonReader& reader, ReadStack& state)
   at System.Text.Json.JsonSerializer.HandleStartArray(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& readStack)
   at System.Text.Json.JsonSerializer.ReadCore(Type returnType, JsonSerializerOptions options, Utf8JsonReader& reader)
   at System.Text.Json.JsonSerializer.ParseCore(String json, Type returnType, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.Deserialize(String json, Type returnType, JsonSerializerOptions options)`

If I can help with more information please just ask.

[dweatherman]

Closing... just noticed project is referencing preview 7. Will retest with 8.

[dweatherman]

Reopening... updated project to preview 8 and same issue occurs.

[scalablecory]

CC @ahsonkhan

[ahsonkhan]

Looks like serialization works fine for ObservableCollection<T> which derives from Collection<T>, but deserialization fails.

Is this behavior expected for 3.0, and is this issue a duplicate of https://github.com/dotnet/corefx/issues/40479?

If so, we should be failing gracefully, potentially with NSE.

[Fact]
public static void ObservableCollection_Bool()
{
    object result = JsonSerializer.Deserialize("[true,false]", typeof(ObservableCollection<bool>));
}

System.Text.Json.Serialization.Tests.CustomConverterTests.ObservableCollection_Bool [FAIL]
        System.Text.Json.JsonException : The JSON value could not be converted to System.Collections.Generic.ICollection`1[System.Boolean]. Path: $ | LineNumber: 0 | BytePositionInLine: 1.
        Stack Trace:
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\ThrowHelper.Serialization.cs(142,0): at System.Text.Json.ThrowHelper.ThrowJsonException(String message, Utf8JsonReader& reader, String path, Exception innerException)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\ThrowHelper.Serialization.cs(39,0): at System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue(Type propertyType, Utf8JsonReader& reader, String path, Exception innerException)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\ReadStackFrame.cs(195,0): at System.Text.Json.ReadStackFrame.CreateEnumerableValue(Utf8JsonReader& reader, ReadStack& state)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\JsonSerializer.Read.HandleArray.cs(65,0): at System.Text.Json.JsonSerializer.HandleStartArray(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& state)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\JsonSerializer.Read.cs(99,0): at System.Text.Json.JsonSerializer.ReadCore(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& readStack)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\JsonSerializer.Read.Helpers.cs(22,0): at System.Text.Json.JsonSerializer.ReadCore(Type returnType, JsonSerializerOptions options, Utf8JsonReader& reader)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\JsonSerializer.Read.String.cs(74,0): at System.Text.Json.JsonSerializer.ParseCore(String json, Type returnType, JsonSerializerOptions options)
          E:\GitHub\Fork\corefx\src\System.Text.Json\src\System\Text\Json\Serialization\JsonSerializer.Read.String.cs(60,0): at System.Text.Json.JsonSerializer.Deserialize(String json, Type returnType, JsonSerializerOptions options)
          E:\GitHub\Fork\corefx\src\System.Text.Json\tests\Serialization\CustomConverterTests.DerivedTypes.cs(16,0): at System.Text.Json.Serialization.Tests.CustomConverterTests.ObservableCollection_Bool()

cc @steveharter, @layomia - please take a look.

[ahsonkhan]

Re-opening until we know which milestone to target.

cc @ericstj - this issue is currently tagged as 3.0 but the fix is in master only.

I believe support for built-in collection types outside of System.Collections and System.Collections.Generic
namespaces is out-of-scope for 3.0. And this issue is about handling the collection type from System.Collections.ObjectModel. This can be vNext only if the change is too risky.

[ahsonkhan]

Moving this to 5.0 since it isn't critical for 3.0.

[ahsonkhan]

Fixed in dotnet/corefx#40654