Preserve HybridCacheEntryOptions.ToDistributedCacheEntryOptions from trimming

src/libraries/Microsoft.Extensions.Caching.Abstractions/src/ILLink/ILLink.Descriptors.xml

@@ -0,0 +1,8 @@
+<linker>
+  <assembly fullname="Microsoft.Extensions.Caching.Abstractions">
+    <!-- Accessed via [UnsafeAccessor] from Microsoft.Extensions.Caching.Hybrid, which the trimmer cannot follow. -->
+    <type fullname="Microsoft.Extensions.Caching.Hybrid.HybridCacheEntryOptions">
+      <method name="ToDistributedCacheEntryOptions" />
+    </type>
+  </assembly>
+</linker>

src/libraries/Microsoft.Extensions.Caching.Abstractions/tests/TrimmingTests/HybridCacheEntryOptionsAccessorTest.cs

@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+using System;
+using System.Runtime.CompilerServices;
+using Microsoft.Extensions.Caching.Distributed;
+using Microsoft.Extensions.Caching.Hybrid;
+
+class Program
+{
+    // Mirrors the access pattern used by Microsoft.Extensions.Caching.Hybrid's DefaultHybridCache.
+    // HybridCacheEntryOptions.ToDistributedCacheEntryOptions is internal and is only reached via
+    // [UnsafeAccessor] from another assembly, which the trimmer cannot follow. It must be preserved
+    // by the ILLink.Descriptors.xml in Microsoft.Extensions.Caching.Abstractions.
+    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "ToDistributedCacheEntryOptions")]
+    extern static DistributedCacheEntryOptions? ToDistributedCacheEntryOptions(HybridCacheEntryOptions options);
+
+    static int Main()
+    {
+        TimeSpan expiration = TimeSpan.FromMinutes(5);
+        HybridCacheEntryOptions options = new() { Expiration = expiration };
+
+        // Throws MissingMethodException if the target method was trimmed away.
+        DistributedCacheEntryOptions? result = ToDistributedCacheEntryOptions(options);
+
+        if (result is null || result.AbsoluteExpirationRelativeToNow != expiration)
+        {
+            return -1;
+        }
+
+        return 100;
+    }
+}

src/libraries/Microsoft.Extensions.Caching.Abstractions/tests/TrimmingTests/Microsoft.Extensions.Caching.Abstractions.TrimmingTests.proj

@@ -0,0 +1,9 @@
+<Project DefaultTargets="Build">
+  <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.props))" />
+
+  <ItemGroup>
+    <TestConsoleAppSourceFiles Include="HybridCacheEntryOptionsAccessorTest.cs" />
+  </ItemGroup>
+
+  <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.targets))" />
+</Project>