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lostmsulostmsu
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enabled an ability to override Python to .NET argument coversion using PyArgConverter attribute
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3 files changed

+134
-4
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3 files changed

+134
-4
lines changed

‎src/embed_tests/TestCustomArgMarshal.cs

Lines changed: 55 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,55 @@
1+
using System;
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using NUnit.Framework;
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using Python.Runtime;
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namespace Python.EmbeddingTest
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{
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class TestCustomArgMarshal
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{
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[OneTimeSetUp]
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public void SetUp()
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{
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PythonEngine.Initialize();
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}
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[OneTimeTearDown]
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public void Dispose()
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{
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PythonEngine.Shutdown();
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}
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[Test]
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public void CustomArgMarshaller()
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{
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var obj = new CustomArgMarshaling();
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using (Py.GIL()) {
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dynamic callWithInt = PythonEngine.Eval("lambda o: o.CallWithInt('42')");
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callWithInt(obj.ToPython());
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}
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Assert.AreEqual(expected: 42, actual: obj.LastArgument);
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}
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}
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[PyArgConverter(typeof(CustomArgConverter))]
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class CustomArgMarshaling {
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public object LastArgument { get; private set; }
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public void CallWithInt(int value) => this.LastArgument = value;
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}
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class CustomArgConverter : DefaultPyArgumentConverter {
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public override bool TryConvertArgument(IntPtr pyarg, Type parameterType, bool needsResolution,
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out object arg, out bool isOut) {
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if (parameterType != typeof(int))
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return base.TryConvertArgument(pyarg, parameterType, needsResolution, out arg, out isOut);
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bool isString = base.TryConvertArgument(pyarg, typeof(string), needsResolution,
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out arg, out isOut);
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if (!isString) return false;
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int number;
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if (!int.TryParse((string)arg, out number)) return false;
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arg = number;
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return true;
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}
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}
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}

‎src/runtime/methodbinder.cs

Lines changed: 36 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,15 @@
11
using System;
22
using System.Collections;
3+
using System.Diagnostics;
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using System.Reflection;
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using System.Text;
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using System.Collections.Generic;
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using System.Linq;
78

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namespace Python.Runtime
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{
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using System.Linq;
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1013
/// <summary>
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/// A MethodBinder encapsulates information about a (possibly overloaded)
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/// managed method, and is responsible for selecting the right method given
@@ -19,16 +22,16 @@ internal class MethodBinder
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public MethodBase[] methods;
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public bool init = false;
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public bool allow_threads = true;
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readonly IPyArgumentConverter pyArgumentConverter = DefaultPyArgumentConverter.Instance;
25+
IPyArgumentConverter pyArgumentConverter;
2326

2427
internal MethodBinder()
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{
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list = new ArrayList();
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}
2831

29-
internal MethodBinder(MethodInfo mi)
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internal MethodBinder(MethodInfo mi): this()
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{
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list = new ArrayList { mi };
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this.AddMethod(mi);
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}
3336

3437
public int Count
@@ -38,6 +41,7 @@ public int Count
3841

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internal void AddMethod(MethodBase m)
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{
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Debug.Assert(!init);
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list.Add(m);
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}
4347

@@ -165,11 +169,40 @@ internal MethodBase[] GetMethods()
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// I'm sure this could be made more efficient.
166170
list.Sort(new MethodSorter());
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methods = (MethodBase[])list.ToArray(typeof(MethodBase));
172+
pyArgumentConverter = this.GetArgumentConverter();
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init = true;
169174
}
170175
return methods;
171176
}
172177

178+
IPyArgumentConverter GetArgumentConverter() {
179+
IPyArgumentConverter converter = null;
180+
Type converterType = null;
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foreach (MethodBase method in this.methods)
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{
183+
var attribute = method.DeclaringType?
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.GetCustomAttributes(typeof(PyArgConverterAttribute), inherit: false)
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.OfType<PyArgConverterAttribute>()
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.SingleOrDefault()
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?? method.DeclaringType?.Assembly
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.GetCustomAttributes(typeof(PyArgConverterAttribute), inherit: false)
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.OfType<PyArgConverterAttribute>()
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.SingleOrDefault();
191+
if (converterType == null)
192+
{
193+
if (attribute == null) continue;
194+
195+
converterType = attribute.ConverterType;
196+
converter = attribute.Converter;
197+
} else if (converterType != attribute?.ConverterType)
198+
{
199+
throw new NotSupportedException("All methods must have the same IPyArgumentConverter");
200+
}
201+
}
202+
203+
return converter ?? DefaultPyArgumentConverter.Instance;
204+
}
205+
173206
/// <summary>
174207
/// Precedence algorithm largely lifted from Jython - the concerns are
175208
/// generally the same so we'll start with this and tweak as necessary.

‎src/runtime/pyargconverter.cs

Lines changed: 43 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -21,8 +21,14 @@ bool TryConvertArgument(IntPtr pyarg, Type parameterType,
2121
bool needsResolution, out object arg, out bool isOut);
2222
}
2323

24+
/// <summary>
25+
/// The implementation of <see cref="IPyArgumentConverter"/> used by default
26+
/// </summary>
2427
public class DefaultPyArgumentConverter: IPyArgumentConverter {
25-
public static DefaultPyArgumentConverter Instance { get; }= new DefaultPyArgumentConverter();
28+
/// <summary>
29+
/// Gets the singleton instance.
30+
/// </summary>
31+
public static DefaultPyArgumentConverter Instance { get; } = new DefaultPyArgumentConverter();
2632

2733
/// <summary>
2834
/// Attempts to convert an argument passed by Python to the specified parameter type.
@@ -44,4 +50,40 @@ public virtual bool TryConvertArgument(
4450
out arg, out isOut);
4551
}
4652
}
53+
54+
/// <summary>
55+
/// Specifies an argument converter to be used, when methods in this class/assembly are called from Python.
56+
/// </summary>
57+
[AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct)]
58+
public class PyArgConverterAttribute : Attribute
59+
{
60+
static readonly Type[] EmptyArgTypeList = new Type[0];
61+
static readonly object[] EmptyArgList = new object[0];
62+
63+
/// <summary>
64+
/// Gets the instance of the converter, that will be used when calling methods
65+
/// of this class/assembly from Python
66+
/// </summary>
67+
public IPyArgumentConverter Converter { get; }
68+
/// <summary>
69+
/// Gets the type of the converter, that will be used when calling methods
70+
/// of this class/assembly from Python
71+
/// </summary>
72+
public Type ConverterType { get; }
73+
74+
/// <summary>
75+
/// Specifies an argument converter to be used, when methods
76+
/// in this class/assembly are called from Python.
77+
/// </summary>
78+
/// <param name="converterType">Type of the converter to use.
79+
/// Must implement <see cref="IPyArgumentConverter"/>.</param>
80+
public PyArgConverterAttribute(Type converterType)
81+
{
82+
if (converterType == null) throw new ArgumentNullException(nameof(converterType));
83+
var ctor = converterType.GetConstructor(EmptyArgTypeList);
84+
if (ctor == null) throw new ArgumentException("Specified converter must have public parameterless constructor");
85+
this.Converter = (IPyArgumentConverter)ctor.Invoke(EmptyArgList);
86+
this.ConverterType = converterType;
87+
}
88+
}
4789
}

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