Hello,

the TCustomJSONRPCHandler.DoCheckParamArray in fpjsonrpc.pp causes an exception with the message "List index (0) out of bounds".

This happens, for example, if ParamArray is empty and there are not required parameter in ParamDef (required not set). In that case ParamArray[i] not exists, so Param:=ParamArray[i] raises "index out of bounds" exception.

I would like to check this before assignment, may be like this

procedure TCustomJSONRPCHandler.DoCheckParamArray(const ParamArray:
TJSONArray);
var
   I : Integer;
   Param: TJSONData;
   Def : TJSONParamDef;
begin
   for I:=0 to ParamDefs.Count-1 do
     begin
     Def:=ParamDefs[i];
     if I>=ParamArray.Count then
       if ParamDefs[i].Required then
         JSONRPCParamError(SErrParamsRequiredParamNotFound,[def.Name]);
     //Check ParamArray.Count first
     if (I<ParamArray.Count) then begin //<< added
       Param:=ParamArray[i];
       // jtUnkown accepts all data types
       if (def.DataTypejtUnknown) and not
(Param.JSONType=def.DataType) then
JSONRPCParamError(SErrParamsDataTypeMismatch,[def.Name,JSONTypeName(def.DataType),JSONTypeName(Param.JSONType)]);
       end;
     end;  //<< added
end;

As it happens, I was working on adding some things to fpjsonrpc, so I fixed this issue by putting the code in an else branch. I pushed that change.

Michael.