Any thoughts on providing JsonObject interop instead of (or with) IDictionary?

[scarletquasar]

Currently, we have ExpandObject or IDictionary<T1, T2> interop to native JavaScript object. Any thought about providing native interop to JsonObject too?

[lahma]

So what is m missing, needed?

[ejsmith]

    [Fact]
    public void CanUseJsonObjectParameter()
    {
        var engine = new Engine();
        string code = "function test(x) { return x.prop1 + '1'; }";
        engine.Execute(code);
        var jsonObject = JsonNode.Parse("""{"prop1": "value1"}""")!.AsObject();
        var result = engine.Invoke("test", jsonObject);
        Assert.Equal("value1", result.ToString());
    }

[ejsmith]

If I just return x.prop1 it works fine, but I am using x.prop1 inside of the function and manipulating it. I get this error:

System.InvalidOperationException: The node must be of type 'JsonObject'.

System.InvalidOperationException
The node must be of type 'JsonObject'.
   at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_NodeWrongType(String typeName)
   at System.Text.Json.Nodes.JsonNode.AsObject()
   at System.Text.Json.Nodes.JsonNode.get_Item(String propertyName)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
--- End of stack trace from previous location ---
   at Jint.Runtime.ExceptionHelper.ThrowMeaningfulException(Engine engine, TargetInvocationException exception)
   at Jint.Runtime.Interop.Reflection.ReflectionAccessor.GetValue(Engine engine, Object target)
   at Jint.Runtime.Descriptors.Specialized.ReflectionDescriptor.get_CustomValue()
   at Jint.Native.Object.ObjectInstance.UnwrapJsValue(PropertyDescriptor desc, JsValue thisObject)
   at Jint.Native.Object.ObjectInstance.Get(JsValue property, JsValue receiver)
   at Jint.Runtime.Interop.ObjectWrapper.Get(JsValue property, JsValue receiver)
   at Jint.Runtime.TypeConverter.OrdinaryToPrimitive(ObjectInstance input, Types hint)
   at Jint.Runtime.TypeConverter.ToPrimitiveObjectInstance(ObjectInstance oi, Types preferredType)
   at Jint.Runtime.Interpreter.Expressions.JintBinaryExpression.PlusBinaryExpression.EvaluateInternal(EvaluationContext context)
   at Jint.Runtime.Interpreter.Expressions.JintExpression.GetValue(EvaluationContext context)
   at Jint.Runtime.Interpreter.Statements.JintReturnStatement.ExecuteInternal(EvaluationContext context)
   at Jint.Runtime.Interpreter.JintStatementList.Execute(EvaluationContext context)
   at Jint.Native.Function.ScriptFunctionInstance.Call(JsValue thisArgument, JsValue[] arguments)
   at Jint.Native.Function.FunctionInstance.Jint.Native.ICallable.Call(JsValue thisObject, JsValue[] arguments)
   at Jint.Engine.<>c__DisplayClass96_0.<Invoke>g__DoInvoke|0()
   at Jint.Engine.ExecuteWithConstraints[T](Boolean strict, Func`1 callback)
   at Jint.Engine.Invoke(JsValue value, Object thisObj, Object[] arguments)
   at Jint.Engine.Invoke(String propertyName, Object thisObj, Object[] arguments)
   at Jint.Engine.Invoke(String propertyName, Object[] arguments)
   at ConcordServicing.Tests.Unit.DataImportTests.CanUseJsonObjectParameter() in D:\Projects\Concord\ConcordServicing\tests\ConcordServicing.Tests\Unit\DataImportTests.cs:line 243
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)

[lahma]

Seems that you would need to access the Value of the target, like so:

[Fact]
public void CanUseJsonObjectParameter()
{
    var engine = new Engine();
    string code = "function test(x) { return x.prop1.value + '1'; }";
    engine.Execute(code);
    var jsonObject = JsonNode.Parse("""{"prop1": "value1"}""")!.AsObject();
    var result = engine.Invoke("test", jsonObject);
    Assert.Equal("value11", result.ToString());
}

Don't know if STJ has some interfaces that would allow getting value directly from property.

[ejsmith]

Yeah, I'd say that is pretty surprising behavior and not what I want. Right now I'm deserializing to a dictionary to make it work, but that seems like a wasteful operation when it seems like JsonObject should be the perfect type already.

[lahma]

New sample for engine configured for better STJ support has landed main: #1663 , your original test case seems to work with it without the .value workaround

[lahma]

New sample for engine configured for better STJ support has landed main: #1663 , as Jint doesn't know STJ type it needs to be taught about it.

[ejsmith]

Thank you!

[ejsmith]

@lahma Your sample worked good for reading values from a JsonObject and JsonArray, but now I'm attempting to mutate those objects in script and expect them to be updated in C# after the script runs and they are unmodified. The Jint interop engine knows about IDictionary and JsonObject implements IDictionary but that doesn't seem to work. I tried digging into things to see if I could figure out how to get it to work, but I haven't had any luck so far. Any ideas or pointers?

[lahma]

I think there's a small problem with the filter, try info.ReflectedType != typeof(JsonObject) && info.Name == "Item" && info is PropertyInfo p (so ReflectedType instead of DeclaringType).

[ejsmith]

Ok, thanks! That got me a little closer. I still needed to implement a type converter for JsonNode. Now it's working great!