runtime: .NET 7 regression in ZipArchive

Description

I ran into this trying to get MAUI workloads running on .NET 7. Our CI caught some test failures here.

Append to an existing ZipEntry with code such as:

using var fileStream = File.Open(path, FileMode.Open, FileAccess.ReadWrite);
using var zip = new ZipArchive(fileStream, ZipArchiveMode.Update);

var oldEntry = zip.GetEntry("foo.txt");
ArgumentNullException.ThrowIfNull(oldEntry);
var newEntry = zip.CreateEntry("foo.txt");

using var newStream = newEntry.Open();

using (var oldStream = oldEntry.Open())
{
    oldStream.CopyTo(newStream);
}

using var writer = new StreamWriter(newStream);
writer.Write("foo");

oldEntry.Delete();

In .NET 6 the code works, in .NET 7 it throws:

Message: 
System.InvalidOperationException : An entry named 'foo.txt' already exists in the archive.

Stack Trace: 
ZipArchive.DoCreateEntry(String entryName, Nullable`1 compressionLevel)
ZipArchive.CreateEntry(String entryName)
ZipArchiveTest.AppendToZip(String path) line 42
ZipArchiveTest.Test1() line 17
RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
RuntimeMethodInfo.InvokeNonEmitUnsafe(Object obj, IntPtr* arguments, Span`1 argsForTemporaryMonoSupport, BindingFlags invokeAttr)

Reproduction Steps

Here is an xunit project targeting both .NET 6 and .NET 7: zippy.zip

If you just unzip and run dotnet test you’ll see it passes on 6 and fails in 7.

Expected behavior

ZipEntry.CreateEntry() doesn’t throw in this example.

Actual behavior

ZipEntry.CreateEntry() throws an exception.

Regression?

Yes, works in .NET 6.

Known Workarounds

There may be a different way to write the above code, but I ported this example from existing code.

Configuration

> dotnet --version
7.0.100-preview.5.22229.2

I’m running on Windows 11, but this also happens on macOS where I saw this on CI.

Other information

I think this may have been introduced in: https://github.com/dotnet/runtime/pull/60973