TO BE CLOSED, CHANGES ON TOP OF MASTER

src/runtime/CollectionWrappers/IterableWrapper.cs

@@ -28,12 +28,16 @@ public IEnumerator<T> GetEnumerator()
             {
                 while (true)
                 {
-                    using var _ = Py.GIL();
-                    if (!iterObject.MoveNext())
+                    T result;
+                    using (Py.GIL())
                     {
-                        break;
+                        if (!iterObject.MoveNext())
+                        {
+                            break;
+                        }
+                        result = iterObject.Current.As<T>()!;
                     }
-                    yield return iterObject.Current.As<T>()!;
+                    yield return result;
                 }
             }
             finally

src/testing/IterableRegressionTester.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+
+using Python.Runtime;
+
+namespace Python.Test
+{
+    public class IterableRegressionTester
+    {
+        public string PartialIterationDoesNotHoldGIL(IEnumerable<object> iterable)
+        {
+            var iterator = iterable.GetEnumerator();
+            try
+            {
+                if (!iterator.MoveNext())
+                {
+                    return "empty";
+                }
+
+                if (DebugUtil.HaveInterpreterLock())
+                {
+                    return "gil_held_after_partial_iteration";
+                }
+
+                return "ok";
+            }
+            finally
+            {
+                iterator.Dispose();
+            }
+        }
+    }
+}

tests/test_codec.py

@@ -5,7 +5,12 @@
 import pytest
 import Python.Runtime
 import Python.Test as Test
-from Python.Test import ListConversionTester, ListMember, CodecResetter
+from Python.Test import (
+    CodecResetter,
+    IterableRegressionTester,
+    ListConversionTester,
+    ListMember,
+)
 
 
 @pytest.fixture(autouse=True)
@@ -59,6 +64,19 @@ def test_iterable():
     assert 3 == ob.GetLength2(iterable2)
 
 
+def test_iterable_partial_iteration_does_not_hold_gil():
+    """Test to ensure partial enumeration does not hold GIL"""
+    Python.Runtime.Codecs.IterableDecoder.Register()
+    probe = IterableRegressionTester()
+
+    result = probe.PartialIterationDoesNotHoldGIL(int_iterable())
+    assert result == "ok", (
+        "Partial iteration blocked managed callback thread; "
+        "IterableWrapper may still be yielding inside Py.GIL(). "
+        f"Probe result: {result}"
+    )
+
+
 def test_sequence():
     Python.Runtime.Codecs.SequenceDecoder.Register()
     ob = ListConversionTester()