Cannot access child value on Newtonsoft.Json.Linq.JValue in OrchardCore

[jptissot]

An unhandled exception has occurred while executing the request.
System.InvalidOperationException: Cannot access child value on Newtonsoft.Json.Linq.JValue.
   at Jint.Runtime.Descriptors.Specialized.IndexDescriptor.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.TypeConverter.OrdinaryToPrimitive(ObjectInstance input, Types hint)
   at Jint.Runtime.TypeConverter.ToPrimitive(JsValue input, Types preferredType)
   at Jint.Runtime.Interpreter.Expressions.JintExpression.EqualUnlikely(JsValue x, JsValue y)
   at Jint.Runtime.Interpreter.Expressions.JintExpression.Equal(JsValue x, JsValue y)
   at Jint.Runtime.Interpreter.Expressions.JintBinaryExpression.EqualBinaryExpression.EvaluateInternal()
   at Jint.Runtime.Interpreter.Expressions.JintBinaryExpression.GetValue()
   at Jint.Runtime.Interpreter.Statements.JintIfStatement.ExecuteInternal()
   at Jint.Runtime.Interpreter.JintStatementList.Execute()
   at Jint.Engine.Execute(Script program)
   at OrchardCore.Scripting.JavaScript.JavaScriptEngine.Evaluate(IScriptingScope scope, String script) in C:\projects\orchardcore\src\OrchardCore\OrchardCore.Scripting.JavaScript\JavaScriptEngine.cs:line 47
   at OrchardCore.Scripting.DefaultScriptingManager.Evaluate(String directive, IFileProvider fileProvider, String basePath, IEnumerable`1 scopedMethodProviders) in C:\projects\orchardcore\src\OrchardCore\OrchardCore.Infrastructure\Scripting\DefaultScriptingManager.cs:line 45

See OrchardCMS/OrchardCore#7452
and OrchardCMS/OrchardCore#7485

[lahma]

I had a quick look and I think this might be the reason:

0f2c39b#diff-cb9f1edd4924c5cce48293a371cbf0f53cfec3693d40c0657c7264f7e1b4b40dL100-L103

We used to swallow this kind of exception and just return Undefined. So probably wasn't working correctly before, now just manifesting the the error. And the root cause is Jint's ToPrimitive handling when it tries to find Symbol from object attributes and JValue doesn't like that at all.