Make it possible to use inherited indexers

danabr · danabr · commit b40da05a3c92 · 2020-10-07T06:39:17.000+02:00
If a class A had indexer, and class B derived from it, Python.NET would
not consider class B to have any indexer.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -30,6 +30,7 @@ details about the cause of the failure
 -    Fix incorrect choice of method to invoke when using keyword arguments.
 -    Fix non-delegate types incorrectly appearing as callable.
 -    Indexers can now be used with interface objects
+-    Fixed a bug where indexers could not be used if they were inherited
 
 ## [2.5.0][] - 2020-06-14
 
diff --git a/src/runtime/classmanager.cs b/src/runtime/classmanager.cs
@@ -389,6 +389,25 @@ private static ClassInfo GetClassInfo(Type type)
                 ci.members[name] = ob;
             }
 
+            if (ci.indexer == null && type.IsClass)
+            {
+                // Indexer may be inherited.
+                var parent = type.BaseType;
+                while (parent != null && ci.indexer == null)
+                {
+                    foreach (var prop in parent.GetProperties()) {
+                        var args = prop.GetIndexParameters();
+                        if (args.GetLength(0) > 0)
+                        {
+                            ci.indexer = new Indexer();
+                            ci.indexer.AddProperty(prop);
+                            break;
+                        }
+                    }
+                    parent = parent.BaseType;
+                }
+            }
+
             return ci;
         }
     }
diff --git a/src/testing/indexertest.cs b/src/testing/indexertest.cs
@@ -411,4 +411,12 @@ public MultiDefaultKeyIndexerTest() : base()
             }
         }
     }
+
+    public class PublicInheritedIndexerTest : PublicIndexerTest { }
+
+    public class ProtectedInheritedIndexerTest : ProtectedIndexerTest { }
+
+    public class PrivateInheritedIndexerTest : ProtectedIndexerTest { }
+
+    public class InternalInheritedIndexerTest : InternalIndexerTest { }
 }
diff --git a/src/tests/test_indexer.py b/src/tests/test_indexer.py
@@ -614,3 +614,25 @@ def test_using_indexer_on_object_without_indexer():
 
     with pytest.raises(TypeError):
         o[0] = 1
+
+
+def test_inherited_indexer():
+    """Test that inherited indexers are accessible"""
+    from Python.Test import PublicInheritedIndexerTest
+    from Python.Test import ProtectedInheritedIndexerTest
+    from Python.Test import PrivateInheritedIndexerTest
+    from Python.Test import InternalInheritedIndexerTest
+
+    pub = PublicInheritedIndexerTest()
+    pub[0] = "zero"
+    assert pub[0] == "zero"
+
+    def assert_no_indexer(obj):
+        with pytest.raises(TypeError):
+            obj[0]
+        with pytest.raises(TypeError):
+            obj[0] = "zero"
+
+    assert_no_indexer(PrivateInheritedIndexerTest)
+    assert_no_indexer(ProtectedInheritedIndexerTest)
+    assert_no_indexer(InternalInheritedIndexerTest)

Original file line number	Diff line number	Diff line change
`@@ -411,4 +411,12 @@ public MultiDefaultKeyIndexerTest() : base()`
`411`	`411`	`}`
`412`	`412`	`}`
`413`	`413`	`}`
	`414`	`+`
	`415`	`+ public class PublicInheritedIndexerTest : PublicIndexerTest { }`
	`416`	`+`
	`417`	`+ public class ProtectedInheritedIndexerTest : ProtectedIndexerTest { }`
	`418`	`+`
	`419`	`+ public class PrivateInheritedIndexerTest : ProtectedIndexerTest { }`
	`420`	`+`
	`421`	`+ public class InternalInheritedIndexerTest : InternalIndexerTest { }`
`414`	`422`	`}`