From 0569d1e41fe32fa18858c593a93b9757c8a48a39 Mon Sep 17 00:00:00 2001
From: John Lambert <john_lambert@sil.org>
Date: Fri, 11 Oct 2024 10:20:01 -0400
Subject: [PATCH 1/2] If there are no enumerators, it enters an infinite loop.

---
 src/SIL.Machine/Utils/EnumerableExtensions.cs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/SIL.Machine/Utils/EnumerableExtensions.cs b/src/SIL.Machine/Utils/EnumerableExtensions.cs
index 1c2fc72b0..8bab692e2 100644
--- a/src/SIL.Machine/Utils/EnumerableExtensions.cs
+++ b/src/SIL.Machine/Utils/EnumerableExtensions.cs
@@ -13,6 +13,8 @@ Func<IEnumerable<TSource>, TResult> selector
         {
             // ToList is necessary to avoid deferred execution
             List<IEnumerator<TSource>> enumerators = source.Select(seq => seq.GetEnumerator()).ToList();
+            if (enumerators.Count == 0)
+                yield break;
             try
             {
                 while (true)

From 4c31e2f1a8559b32502907d9ed0749824d17a8ab Mon Sep 17 00:00:00 2001
From: John Lambert <john_lambert@sil.org>
Date: Fri, 11 Oct 2024 15:10:54 -0400
Subject: [PATCH 2/2] Add test

---
 .../Utils/EnumberableExtensionTests.cs        | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 tests/SIL.Machine.Tests/Utils/EnumberableExtensionTests.cs

diff --git a/tests/SIL.Machine.Tests/Utils/EnumberableExtensionTests.cs b/tests/SIL.Machine.Tests/Utils/EnumberableExtensionTests.cs
new file mode 100644
index 000000000..7524087e1
--- /dev/null
+++ b/tests/SIL.Machine.Tests/Utils/EnumberableExtensionTests.cs
@@ -0,0 +1,23 @@
+using NUnit.Framework;
+
+namespace SIL.Machine.Utils;
+
+[TestFixture]
+public class EnumerableExtensionTests
+{
+    [Test]
+    public void ZipMany_None()
+    {
+        var seqs = new List<IEnumerable<int>>();
+        IEnumerable<int> result = seqs.ZipMany(x => x.Sum());
+        Assert.That(result, Is.Empty);
+    }
+
+    [Test]
+    public void ZipMany_Two()
+    {
+        var seqs = new List<IEnumerable<int>> { new[] { 1, 2, 3 }, new[] { 4, 5, 6 } };
+        IEnumerable<int> result = seqs.ZipMany(x => x.Sum());
+        Assert.That(result, Is.EqualTo(new[] { 5, 7, 9 }));
+    }
+}