MongoDb GetCollection error: get MakeGenericMethod may only be called on a method for which MethodBase.IsGenericMethodDefinition is true. #816

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1. slozier

   added

   confirmed

   Port to ipy3

   on May 24, 2022
2. slozier commented on May 24, 2022

   

   slozier

   on May 24, 2022

   Last edited by slozier

   Contributor

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   The issue appears to be something like this:

   public abstract class MyBaseClass {
       public abstract T GetCollection<T>();
   
       // this is just a helper to get an instance of the internal class
       public static MyBaseClass test() {
           return new MyInternalClass();
       }
   }
   
   internal sealed class MyInternalClass : MyBaseClass {
       public override T GetCollection<T>() {
           throw new NotImplementedException();
       }
   }

   MyBaseClass.test().GetCollection[object]

   which results in:

   SystemError: T GetCollection[T]() is not a GenericMethodDefinition. MakeGenericMethod may only be called on a method for which MethodBase.IsGenericMethodDefinition is true.
   

   A possible workaround is to enable private bindings with the PrivateBinding option.
3. bnuzhouwei commented on May 25, 2022

   

   bnuzhouwei

   on May 25, 2022

   Last edited by bnuzhouwei

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   Thanks, you are right, the code in mongodb driver is:

   namespace MongoDB.Driver
   {
   	// Token: 0x020000C0 RID: 192
   	internal sealed class MongoDatabaseImpl : MongoDatabaseBase
   }
   

   Internal without public....,

   But how to to enable private bindings with the PrivateBinding option? Can add any paramters to the CreateEngine method?

   IronPython.Hosting.Python.CreateEngine()
4. bnuzhouwei commented on May 25, 2022

   

   bnuzhouwei

   on May 25, 2022

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   I modified the source code, changed the class MongoDatabaseImpl from internal to public, and recompile it.

   namespace MongoDB.Driver
   {
   	public sealed class MongoDatabaseImpl : MongoDatabaseBase
   }

   The GetCollection in above code run correctly, but in mongodb, there are many methods with default value as default(CancellationToken), i.e.

   long CountDocuments(FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken));

   but in IronPython, when we call the method:

   GetCollection[BsonDocument]("collection")

   got

   IronPython.Runtime.Exceptions.TypeErrorException: expected CancellationToken, got NoneType

   I seems that IronPython does't support default value for structs, such as default(CancellationToken)
5. slozier commented on May 25, 2022

   

   slozier

   on May 25, 2022

   Last edited by slozier

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   But how to to enable private bindings with the PrivateBinding option? Can add any paramters to the CreateEngine method?

   You can enable private binding like this:

   Python.CreateEngine(new Dictionary<string, object> { {"PrivateBinding", true} });