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koubaakoubaa
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Provide hook to implement __repr__
Issue: 680
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‎AUTHORS.md‎

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@@ -36,6 +36,7 @@
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- Luke Stratman ([@lstratman](https://github.com/lstratman))
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- Konstantin Posudevskiy ([@konstantin-posudevskiy](https://github.com/konstantin-posudevskiy))
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- Matthias Dittrich ([@matthid](https://github.com/matthid))
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- Mohamed Koubaa ([@koubaa](https://github.com/koubaa))
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- Patrick Stewart ([@patstew](https://github.com/patstew))
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- Raphael Nestler ([@rnestler](https://github.com/rnestler))
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- Rickard Holmberg ([@rickardraysearch](https://github.com/rickardraysearch))

‎CHANGELOG.md‎

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@@ -23,6 +23,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
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- Incorporated reference-style links to issues and pull requests in the CHANGELOG ([#608][i608])
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- Added detailed comments about aproaches and dangers to handle multi-app-domains ([#625][p625])
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- Python 3.7 support, builds and testing added. Defaults changed from Python 3.6 to 3.7 ([#698][p698])
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- Added support for C# types to provide `__repr__` ([#680][p680])
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### Changed
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‎src/runtime/classbase.cs‎

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@@ -233,7 +233,75 @@ public static IntPtr tp_str(IntPtr ob)
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}
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try
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{
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//As per python doc:
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//The return value must be a string object. If a class defines __repr__() but not __str__(),
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//then __repr__() is also used when an “informal” string representation of instances of that
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//class is required.
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//In C#, everything provides ToString(), so the check here will be whether the type explicitly
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//provides ToString() or if it is language provided (i.e. the fully qualified type name as a string)
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//First check which type in the object hierarchy provides ToString()
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//ToString has two "official" overloads so loop over GetMethods to get the one without parameters
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var instType = co.inst.GetType();
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foreach (var method in instType.GetMethods())
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{
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//TODO this could probably be done more cleanly with Linq
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if (!method.IsPublic) continue; //skip private/protected methods
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if (method.Name != "ToString") continue; //only look for ToString
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if (method.DeclaringType == typeof(object)) continue; //ignore default from object
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if (method.GetParameters().Length != 0) continue; //ignore Formatter overload of ToString
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//match! something other than object provides a parameter-less overload of ToString
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return Runtime.PyString_FromString(co.inst.ToString());
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}
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//If the object defines __repr__, call it.
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System.Reflection.MethodInfo reprMethodInfo = instType.GetMethod("__repr__");
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if (reprMethodInfo != null && reprMethodInfo.IsPublic)
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{
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var reprString = reprMethodInfo.Invoke(co.inst, null) as string;
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return Runtime.PyString_FromString(reprString);
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}
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//otherwise fallback to object's ToString() implementation
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return Runtime.PyString_FromString(co.inst.ToString());
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}
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catch (Exception e)
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{
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if (e.InnerException != null)
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{
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e = e.InnerException;
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}
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Exceptions.SetError(e);
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return IntPtr.Zero;
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}
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}
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public static IntPtr tp_repr(IntPtr ob)
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{
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var co = GetManagedObject(ob) as CLRObject;
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if (co == null)
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{
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return Exceptions.RaiseTypeError("invalid object");
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}
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try
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{
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//if __repr__ is defined, use it
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var instType = co.inst.GetType();
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System.Reflection.MethodInfo methodInfo = instType.GetMethod("__repr__");
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if (methodInfo != null && methodInfo.IsPublic)
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{
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var reprString = methodInfo.Invoke(co.inst, null) as string;
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return Runtime.PyString_FromString(reprString);
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}
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//otherwise use the standard object.__repr__(inst)
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IntPtr args = Runtime.PyTuple_New(1);
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Runtime.PyTuple_SetItem(args, 0, ob);
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IntPtr reprFunc = Runtime.PyObject_GetAttrString(Runtime.PyBaseObjectType, "__repr__");
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return Runtime.PyObject_Call(reprFunc, args, IntPtr.Zero);
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}
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catch (Exception e)
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{

‎src/runtime/exceptions.cs‎

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@@ -36,6 +36,29 @@ internal static Exception ToException(IntPtr ob)
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return e;
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}
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/// <summary>
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/// Exception __repr__ implementation
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/// </summary>
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public static IntPtr tp_repr(IntPtr ob)
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{
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Exception e = ToException(ob);
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if (e == null)
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{
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return Exceptions.RaiseTypeError("invalid object");
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}
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string name = e.GetType().Name;
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string message;
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if (e.Message != String.Empty)
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{
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message = String.Format("{0}('{1}')", name, e.Message);
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}
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else
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{
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message = String.Format("{0}()", name);
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}
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return Runtime.PyUnicode_FromString(message);
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}
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/// <summary>
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/// Exception __str__ implementation
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/// </summary>

‎src/testing/Python.Test.csproj‎

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<Compile Include="threadtest.cs" />
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<Compile Include="doctest.cs" />
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<Compile Include="subclasstest.cs" />
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<Compile Include="reprtest.cs" />
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</ItemGroup>
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<ItemGroup>
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<Reference Include="Microsoft.CSharp" />

‎src/testing/ReprTest.cs‎

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using System;
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using System.Text;
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namespace Python.Test
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{
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/// <summary>
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/// Supports repr unit tests.
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/// </summary>
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public class ReprTest
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{
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public class Point
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{
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public Point(double x, double y)
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{
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X = x;
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Y = y;
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}
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public double X { get; set; }
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public double Y { get; set; }
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public override string ToString()
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{
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return base.ToString() + ": X=" + X.ToString() + ", Y=" + Y.ToString();
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}
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public string __repr__()
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{
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return "Point(" + X.ToString() + "," + Y.ToString() + ")";
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}
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}
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public class Foo
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{
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public string __repr__()
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{
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return "I implement __repr__() but not ToString()!";
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}
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}
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public class Bar
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{
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public override string ToString()
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{
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return "I implement ToString() but not __repr__()!";
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}
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}
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public class BazBase
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{
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public override string ToString()
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{
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return "Base class implementing ToString()!";
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}
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}
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public class BazMiddle : BazBase
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{
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public override string ToString()
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{
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return "Middle class implementing ToString()!";
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}
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}
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//implements ToString via BazMiddle
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public class Baz : BazMiddle
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{
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}
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public class Quux
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{
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public string ToString(string format)
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{
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return "I implement ToString() with an argument!";
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}
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}
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public class QuuzBase
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{
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protected string __repr__()
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{
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return "I implement __repr__ but it isn't public!";
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}
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}
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public class Quuz : QuuzBase
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{
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}
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public class Corge
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{
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public string __repr__(int i)
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{
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return "__repr__ implemention with input parameter!";
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}
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}
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public class Grault
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{
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public int __repr__()
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{
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return "__repr__ implemention with wrong return type!".Length;
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}
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}
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}
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}

‎src/tests/test_repr.py‎

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# -*- coding: utf-8 -*-
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"""Test __repr__ output"""
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import System
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import pytest
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from Python.Test import ReprTest
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def test_basic():
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"""Test Point class which implements both ToString and __repr__ without inheritance"""
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ob = ReprTest.Point(1,2)
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# point implements ToString() and __repr__()
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assert ob.__repr__() == "Point(1,2)"
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assert str(ob) == "Python.Test.ReprTest+Point: X=1, Y=2"
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def test_system_string():
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"""Test system string"""
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ob = System.String("hello")
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assert str(ob) == "hello"
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assert "<System.String object at " in ob.__repr__()
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def test_repr_only():
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"""Test class implementing __repr__() but not ToString()"""
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ob = ReprTest.Foo()
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assert str(ob) == "I implement __repr__() but not ToString()!"
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assert ob.__repr__() == "I implement __repr__() but not ToString()!"
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def test_str_only():
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"""Test class implementing ToString() but not __repr__()"""
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ob = ReprTest.Bar()
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assert str(ob) == "I implement ToString() but not __repr__()!"
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assert "<Python.Test.Bar object at " in ob.__repr__()
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def test_hierarchy1():
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"""Test inheritance heirarchy with base & middle class implementing ToString"""
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ob1 = ReprTest.BazBase()
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assert str(ob1) == "Base class implementing ToString()!"
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assert "<Python.Test.BazBase object at " in ob1.__repr__()
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ob2 = ReprTest.BazMiddle()
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assert str(ob2) == "Middle class implementing ToString()!"
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assert "<Python.Test.BazMiddle object at " in ob2.__repr__()
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ob3 = ReprTest.Baz()
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assert str(ob3) == "Middle class implementing ToString()!"
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assert "<Python.Test.Baz object at " in ob3.__repr__()
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def bad_tostring():
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"""Test ToString that can't be used by str()"""
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ob = ReprTest.Quux()
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assert str(ob) == "Python.Test.ReprTest+Quux"
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assert "<Python.Test.Quux object at " in ob.__repr__()
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def bad_repr():
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"""Test incorrect implementation of repr"""
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ob1 = ReprTest.QuuzBase()
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assert str(ob1) == "Python.Test.ReprTest+QuuzBase"
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assert "<Python.Test.QuuzBase object at " in ob.__repr__()
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ob2 = ReprTest.Quuz()
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assert str(ob2) == "Python.Test.ReprTest+Quuz"
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assert "<Python.Test.Quuz object at " in ob.__repr__()
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ob3 = ReprTest.Corge()
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with pytest.raises(Exception):
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str(ob3)
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with pytest.raises(Exception):
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ob3.__repr__()
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ob4 = ReprTest.Grault()
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with pytest.raises(Exception):
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str(ob4)
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with pytest.raises(Exception):
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ob4.__repr__()

‎src/tests/tests.pyproj‎

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<Compile Include="test_recursive_types.py" />
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<Compile Include="test_subclass.py" />
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<Compile Include="test_thread.py" />
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<Compile Include="test_repr.py" />
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<Compile Include="utils.py" />
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<Compile Include="fixtures\argv-fixture.py" />
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</ItemGroup>

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