introduced IPyArgumentConverter interface, that controls marshaling o…

…f Python objects when calling .NET methods
pythonnet · lostmsu · Mar 28, 2019 · Mar 28, 2019 · Mar 28, 2019 · Mar 29, 2019
commit c355bd6995487eb5d0c993821f97a02207290a4c
diff --git a/src/runtime/methodbinder.cs b/src/runtime/methodbinder.cs
@@ -19,6 +19,7 @@ internal class MethodBinder
         public MethodBase[] methods;
         public bool init = false;
         public bool allow_threads = true;
+        readonly IPyArgumentConverter pyArgumentConverter = DefaultPyArgumentConverter.Instance;
 
         internal MethodBinder()
         {
@@ -326,7 +327,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
                     continue;
                 }
                 var outs = 0;
-                var margs = TryConvertArguments(pi, paramsArray, args, pynargs, kwargDict, defaultArgList,
+                var margs = this.TryConvertArguments(pi, paramsArray, args, pynargs, kwargDict, defaultArgList,
                     needsResolution: _methods.Length > 1,
                     outs: out outs);
 
@@ -382,7 +383,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
         /// <param name="needsResolution"><c>true</c>, if overloading resolution is required</param>
         /// <param name="outs">Returns number of output parameters</param>
         /// <returns>An array of .NET arguments, that can be passed to a method.</returns>
-        static object[] TryConvertArguments(ParameterInfo[] pi, bool paramsArray,
+        object[] TryConvertArguments(ParameterInfo[] pi, bool paramsArray,
             IntPtr args, int pyArgCount,
             Dictionary<string, IntPtr> kwargDict,
             ArrayList defaultArgList,
@@ -423,7 +424,9 @@ static object[] TryConvertArguments(ParameterInfo[] pi, bool paramsArray,
                 }
 
                 bool isOut;
-                if (!TryConvertArgument(op, parameter.ParameterType, needsResolution, out margs[paramIndex], out isOut))
+                if (!this.pyArgumentConverter.TryConvertArgument(
+                    op, parameter.ParameterType, needsResolution,
+                    out margs[paramIndex], out isOut))
                 {
                     return null;
                 }
@@ -445,7 +448,7 @@ static object[] TryConvertArguments(ParameterInfo[] pi, bool paramsArray,
             return margs;
         }
 
-        static bool TryConvertArgument(IntPtr op, Type parameterType, bool needsResolution,
+        internal static bool TryConvertArgument(IntPtr op, Type parameterType, bool needsResolution,
                                        out object arg, out bool isOut)
         {
             arg = null;

diff --git a/src/runtime/pyargconverter.cs b/src/runtime/pyargconverter.cs
@@ -0,0 +1,47 @@
+namespace Python.Runtime {
+    using System;
+
+    /// <summary>
+    /// Specifies how to convert Python objects, passed to .NET functions to the expected CLR types.
+    /// </summary>
+    public interface IPyArgumentConverter
+    {
+        /// <summary>
+        /// Attempts to convert an argument passed by Python to the specified parameter type.
+        /// </summary>
+        /// <param name="pyarg">Unmanaged pointer to the Python argument value</param>
+        /// <param name="parameterType">The expected type of the parameter</param>
+        /// <param name="needsResolution"><c>true</c> if the method is overloaded</param>
+        /// <param name="arg">This parameter will receive the converted value, matching the specified type</param>
+        /// <param name="isOut">This parameter will be set to <c>true</c>,
+        /// if the final type needs to be marshaled as an out argument.</param>
+        /// <returns><c>true</c>, if the object matches requested type,
+        /// and conversion was successful, otherwise <c>false</c></returns>
+        bool TryConvertArgument(IntPtr pyarg, Type parameterType,
+            bool needsResolution, out object arg, out bool isOut);
+    }
+
+    public class DefaultPyArgumentConverter: IPyArgumentConverter {
+        public static DefaultPyArgumentConverter Instance { get; }= new DefaultPyArgumentConverter();
+
+        /// <summary>
+        /// Attempts to convert an argument passed by Python to the specified parameter type.
+        /// </summary>
+        /// <param name="pyarg">Unmanaged pointer to the Python argument value</param>
+        /// <param name="parameterType">The expected type of the parameter</param>
+        /// <param name="needsResolution"><c>true</c> if the method is overloaded</param>
+        /// <param name="arg">This parameter will receive the converted value, matching the specified type</param>
+        /// <param name="isOut">This parameter will be set to <c>true</c>,
+        /// if the final type needs to be marshaled as an out argument.</param>
+        /// <returns><c>true</c>, if the object matches requested type,
+        /// and conversion was successful, otherwise <c>false</c></returns>
+        public virtual bool TryConvertArgument(
+            IntPtr pyarg, Type parameterType, bool needsResolution,
+            out object arg, out bool isOut)
+        {
+            return MethodBinder.TryConvertArgument(
+                pyarg, parameterType, needsResolution,
+                out arg, out isOut);
+        }
+    }
+}