Clone the items when IEnumerable.DeepClone() is called, not on each enumeration - #85
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…numeration DeepClone(this IEnumerable<T>) returned source.Select(DeepClone), a lazy view over the live source. Each enumeration cloned every item again, so edits to the cloned items were lost on the next read, and the clone followed later changes to the source. Materialize the clones when the method is called. Also null-check the source there and in Stack<T>.DeepClone, like the other overloads. Fixes #80 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KaXGMeYeXB1J32kSrLGhgJ
Keeps them clear of the tests other open PRs append to SpecializedCollectionTests.cs. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KaXGMeYeXB1J32kSrLGhgJ
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This was referenced Sep 28, 2026
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Fixes #80
What was wrong
DeepClone<T>(this IEnumerable<T>)returnedsource.Select(DeepClone), which is lazy. The result was a view over the live source, and each time it was enumerated every item was cloned again. Three consequences:clone.First()returned a different instance on every call.src.Clear(),clone.Count()returned 0.Lists, arrays, queues and the other collections the README lists as supported all bind to this overload, so the problem affected the library's main use case.
Change
DeepClone()is called ([.. source.Select(DeepClone)]). The result is a snapshot. The XML doc now says so.IEnumerable<T>.DeepCloneandStack<T>.DeepClonenow callEnsure.NotNull(source), like the other overloads.Behaviour change for the changelog: the result is no longer lazy. Code that relied on the clone following the source will see a snapshot now. That is the behaviour the method's doc already promised ("A new collection containing deep clones").
Tests
Enumerable_DeepClone_ShouldKeepEditsAcrossEnumerationsandEnumerable_DeepClone_ShouldNotTrackSourceChangesfail without the library change and pass with it.Enumerable_DeepClone_NullSource_ShouldThrowandStack_DeepClone_NullSource_ShouldThrowguard the null contract. They already passed before this change, because LINQ threw on a null source anyway.dotnet test: 46/46 pass. The two multiple-enumeration tests suppress CA1851 locally, because enumerating twice is exactly what they check.This touches a different part of
DeepCloneContainerExtensions.csfrom #84, so the two PRs don't conflict.🤖 Generated with Claude Code
https://claude.ai/code/session_01KaXGMeYeXB1J32kSrLGhgJ
Generated by Claude Code