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lostmsulostmsu
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allow .NET classes to override __getattr__ and __setattr__
1 parent a8a9426 commit eb6577f

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7 files changed

+145
-14
lines changed

7 files changed

+145
-14
lines changed

‎CHANGELOG.md

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@@ -10,6 +10,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
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### Added
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- Added automatic NuGet package generation in appveyor and local builds
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- Added IGetAttr and ISetAttr, so that .NET classes could override __getattr__ and __setattr__
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### Changed
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‎src/embed_tests/Python.EmbeddingTest.csproj

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@@ -89,6 +89,7 @@
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<Compile Include="TestDomainReload.cs" />
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<Compile Include="TestExample.cs" />
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<Compile Include="TestFinalizer.cs" />
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<Compile Include="TestInstanceWrapping.cs" />
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<Compile Include="TestPyAnsiString.cs" />
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<Compile Include="TestPyFloat.cs" />
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<Compile Include="TestPyInt.cs" />

‎src/embed_tests/TestInstanceWrapping.cs

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@@ -0,0 +1,60 @@
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using NUnit.Framework;
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using Python.Runtime;
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using Python.Runtime.Slots;
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namespace Python.EmbeddingTest {
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public class TestInstanceWrapping {
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[OneTimeSetUp]
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public void SetUp() {
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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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PythonEngine.Shutdown();
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}
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[Test]
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public void GetAttrCanBeOverriden() {
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var overloaded = new Overloaded();
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using (Py.GIL()) {
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var o = overloaded.ToPython();
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dynamic getNonexistingAttr = PythonEngine.Eval("lambda o: o.non_existing_attr");
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string nonexistentAttrValue = getNonexistingAttr(o);
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Assert.AreEqual(GetAttrFallbackValue, nonexistentAttrValue);
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}
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}
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[Test]
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public void SetAttrCanBeOverriden() {
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var overloaded = new Overloaded();
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using (Py.GIL())
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using (var scope = Py.CreateScope()) {
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var o = overloaded.ToPython();
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scope.Set(nameof(o), o);
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scope.Exec($"{nameof(o)}.non_existing_attr = 42");
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Assert.AreEqual(42, overloaded.Value);
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}
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}
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const string GetAttrFallbackValue = "undefined";
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class Base {}
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class Derived: Base { }
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class Overloaded: Derived, IGetAttr, ISetAttr
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{
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public int Value { get; private set; }
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public bool TryGetAttr(string name, out PyObject value) {
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value = GetAttrFallbackValue.ToPython();
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return true;
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}
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public bool TrySetAttr(string name, PyObject value) {
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this.Value = value.As<int>();
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return true;
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}
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}
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}
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}

‎src/runtime/Python.Runtime.csproj

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@@ -22,19 +22,19 @@
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</PropertyGroup>
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<!--We can relax binding to platform because code references no any platform dependent assemblies-->
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<!--This will allows to use any build of this assebly as a compile ref assebly-->
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<!--<PropertyGroup Condition=" '$(Platform)' == 'x86'">
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<PlatformTarget>x86</PlatformTarget>
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Platform)' == 'x64'">
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<PlatformTarget>x64</PlatformTarget>
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<!--<PropertyGroup Condition=" '$(Platform)' == 'x86'">
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<PlatformTarget>x86</PlatformTarget>
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Platform)' == 'x64'">
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<PlatformTarget>x64</PlatformTarget>
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</PropertyGroup>-->
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<PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMono'">
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON2;PYTHON27;UCS4</DefineConstants>
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<Optimize>true</Optimize>
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<DebugType>pdbonly</DebugType>
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMonoPY3'">
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4</DefineConstants>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4</DefineConstants>
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<Optimize>true</Optimize>
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<DebugType>pdbonly</DebugType>
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</PropertyGroup>
@@ -46,7 +46,7 @@
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Configuration)' == 'DebugMonoPY3'">
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<DebugSymbols>true</DebugSymbols>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4;TRACE;DEBUG</DefineConstants>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4;TRACE;DEBUG</DefineConstants>
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<Optimize>false</Optimize>
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<DebugType>full</DebugType>
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</PropertyGroup>
@@ -56,7 +56,7 @@
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<DebugType>pdbonly</DebugType>
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWinPY3'">
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2</DefineConstants>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2</DefineConstants>
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<Optimize>true</Optimize>
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<DebugType>pdbonly</DebugType>
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</PropertyGroup>
@@ -68,7 +68,7 @@
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</PropertyGroup>
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<PropertyGroup Condition=" '$(Configuration)' == 'DebugWinPY3'">
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<DebugSymbols>true</DebugSymbols>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2;TRACE;DEBUG</DefineConstants>
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<DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2;TRACE;DEBUG</DefineConstants>
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<Optimize>false</Optimize>
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<DebugType>full</DebugType>
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</PropertyGroup>
@@ -137,11 +137,12 @@
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<Compile Include="pythonexception.cs" />
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<Compile Include="pytuple.cs" />
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<Compile Include="runtime.cs" />
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<Compile Include="slots.cs" />
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<Compile Include="typemanager.cs" />
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<Compile Include="typemethod.cs" />
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<Compile Include="Util.cs" />
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<Compile Include="platform\Types.cs" />
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<Compile Include="platform\LibraryLoader.cs" />
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<Compile Include="platform\Types.cs" />
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<Compile Include="platform\LibraryLoader.cs" />
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</ItemGroup>
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<ItemGroup Condition=" '$(PythonInteropFile)' != '' ">
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<Compile Include="$(PythonInteropFile)" />
@@ -151,7 +152,7 @@
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<Compile Include="interop34.cs" />
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<Compile Include="interop35.cs" />
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<Compile Include="interop36.cs" />
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<Compile Include="interop37.cs" />
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<Compile Include="interop37.cs" />
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</ItemGroup>
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<ItemGroup>
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<None Include="..\pythonnet.snk" />
@@ -170,4 +171,4 @@
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<Copy SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
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<!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
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</Target>
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</Project>
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</Project>

‎src/runtime/runtime.cs

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@@ -562,6 +562,14 @@ internal static unsafe void XIncref(IntPtr op)
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#endif
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}
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/// <summary>
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/// Increase Python's ref counter for the given object, and return the object back.
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/// </summary>
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internal static IntPtr SelfIncRef(IntPtr op) {
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XIncref(op);
570+
return op;
571+
}
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internal static unsafe void XDecref(IntPtr op)
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{
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#if PYTHON_WITH_PYDEBUG || NETSTANDARD

‎src/runtime/slots.cs

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using System;
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namespace Python.Runtime.Slots
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{
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/// <summary>
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/// Implement this interface to override Python's __getattr__ for your class
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/// </summary>
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public interface IGetAttr {
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bool TryGetAttr(string name, out PyObject value);
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}
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/// <summary>
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/// Implement this interface to override Python's __setattr__ for your class
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/// </summary>
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public interface ISetAttr {
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bool TrySetAttr(string name, PyObject value);
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}
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static class SlotOverrides {
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public static IntPtr tp_getattro(IntPtr ob, IntPtr key) {
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IntPtr genericResult = Runtime.PyObject_GenericGetAttr(ob, key);
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if (genericResult != IntPtr.Zero || !Runtime.PyString_Check(key)) {
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return genericResult;
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}
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Exceptions.Clear();
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var self = (IGetAttr)((CLRObject)ManagedType.GetManagedObject(ob)).inst;
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string attr = Runtime.GetManagedString(key);
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return self.TryGetAttr(attr, out var value)
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? Runtime.SelfIncRef(value.Handle)
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: Runtime.PyObject_GenericGetAttr(ob, key);
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}
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public static int tp_setattro(IntPtr ob, IntPtr key, IntPtr val) {
36+
if (!Runtime.PyString_Check(key)) {
37+
return Runtime.PyObject_GenericSetAttr(ob, key, val);
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}
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var self = (ISetAttr)((CLRObject)ManagedType.GetManagedObject(ob)).inst;
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string attr = Runtime.GetManagedString(key);
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return self.TrySetAttr(attr, new PyObject(Runtime.SelfIncRef(val)))
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? 0
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: Runtime.PyObject_GenericSetAttr(ob, key, val);
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}
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}
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}

‎src/runtime/typemanager.cs

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@@ -4,10 +4,10 @@
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using System.Reflection;
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using System.Runtime.InteropServices;
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using Python.Runtime.Platform;
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using Python.Runtime.Slots;
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namespace Python.Runtime
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{
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/// <summary>
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/// The TypeManager class is responsible for building binary-compatible
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/// Python type objects that are implemented in managed code.
@@ -155,6 +155,14 @@ internal static IntPtr CreateType(ManagedType impl, Type clrType)
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InitializeSlots(type, impl.GetType());
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158+
if (typeof(IGetAttr).IsAssignableFrom(clrType)) {
159+
InitializeSlot(type, TypeOffset.tp_getattro, typeof(SlotOverrides).GetMethod(nameof(SlotOverrides.tp_getattro)));
160+
}
161+
162+
if (typeof(ISetAttr).IsAssignableFrom(clrType)) {
163+
InitializeSlot(type, TypeOffset.tp_setattro, typeof(SlotOverrides).GetMethod(nameof(SlotOverrides.tp_setattro)));
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}
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if (base_ != IntPtr.Zero)
159167
{
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Marshal.WriteIntPtr(type, TypeOffset.tp_base, base_);
@@ -779,6 +787,11 @@ static void InitializeSlot(IntPtr type, IntPtr slot, string name)
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Marshal.WriteIntPtr(type, offset, slot);
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}
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790+
static void InitializeSlot(IntPtr type, int slotOffset, MethodInfo method) {
791+
IntPtr thunk = Interop.GetThunk(method);
792+
Marshal.WriteIntPtr(type, slotOffset, thunk);
793+
}
794+
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/// <summary>
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/// Given a newly allocated Python type object and a managed Type that
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/// implements it, initialize any methods defined by the Type that need

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