possible bug: serialization of BooleanClause / Occurs (implementation of Parameter)

[Moray McConnachie]

Please let me know if this would be a question better addressed to dev. 
I have not posted this as a bug issue on the incubator, because I'm not 
sure if it is a bug or I'm just missing something.

I'm upgrading from an earlier installation of Lucene.NET 1.x to using 
Lucene.NET 2.0.004.

Our application uses a client-server architecture. The client 
application serializes a Query object and sends it to the server. The 
server runs the query and returns results.

The client/server operation is handled using .NET remoting which uses 
standard .NET binary serialisation. This is very effective and fast in 
our application.

The issue I have in upgrading to v2 is that the occur member of a 
BooleanClause object is not being deserialized correctly, with the 
result that  queries do not pass from client to server correctly.

occur is of type Occur, which inherits from Parameter, a class which 
supplies  Enum-replacements.

On looking into the code, I do not see how objects inheriting from 
Parameter will ever correctly be deserialized, because there is a static 
collection of strings definining the enums in Parameter which won't get 
serialized.

I have been able to get round the issue by intercepting the 
serialisation and deserialisation of BooleanClause, constructing a 
temporary string variable, like this

private string _occurSerialized=null;

//HACK set up BooleanClause for serialisation
       [System.Runtime.Serialization.OnSerializing()]
       internal void 
OnSerializingMethod(System.Runtime.Serialization.StreamingContext context)
       {
           _occurSerialized = occur.ToString();
       }

       [System.Runtime.Serialization.OnDeserialized()]
       internal void 
OnDeserializedMethod(System.Runtime.Serialization.StreamingContext context)
       {
           switch (_occurSerialized.ToString())
           {
               case "+":
                   occur = Occur.MUST;
                   break;
               case "-":
                   occur = Occur.MUST_NOT;
                   break;
               default:
                   occur = Occur.SHOULD;
                   break;
           }
           _occurSerialized = null;
       }

However, this is bad in the long term since

a) if the enums ever change it will need to be rewritten, and

b) it is not general across other things that may need to be serialized 
which inherit from Parameter

I could do with someone who knows more about the fundamental structures 
in Lucene helping me out with this...

Thanks,
Moray