Ampr: fix path case on Linux (#750)

tests/SharpEmu.Libs.Tests/Ampr/AmprFileRegistryTests.cs

@@ -6,6 +6,9 @@ using Xunit;
 
 namespace SharpEmu.Libs.Tests.Ampr;
 
+// AmprFileRegistry is process-global static state, so the classes that index
+// or clear it must not run concurrently with each other.
+[Collection("AmprFileRegistry")]
 public class AmprFileRegistryTests
 {
     [Fact]
@@ -62,6 +65,79 @@ public class AmprFileRegistryTests
         Assert.Equal(host, d);
     }
 
+    [Fact]
+    public void App0_index_cache_keeps_files_that_differ_only_by_case()
+    {
+        var root = Path.Combine(Path.GetTempPath(), "sharpemu-ampr-case-" + Guid.NewGuid().ToString("N"));
+        var cacheDir = Path.Combine(root, "..", "sharpemu-ampr-cache-" + Guid.NewGuid().ToString("N"));
+        var upper = Path.Combine(root, "data", "ASSET.bin");
+        var lower = Path.Combine(root, "data", "asset.bin");
+        var previousCacheDir = Environment.GetEnvironmentVariable("SHARPEMU_AMPR_INDEX_CACHE");
+        try
+        {
+            Directory.CreateDirectory(Path.Combine(root, "sce_sys"));
+            Directory.CreateDirectory(Path.Combine(root, "data"));
+            File.WriteAllText(Path.Combine(root, "sce_sys", "param.json"), "{}");
+            File.WriteAllBytes(upper, [1, 2, 3]);
+            if (File.Exists(lower))
+            {
+                // Case-insensitive host: the two names are one file, so there is
+                // nothing for an ignore-case index to lose.
+                return;
+            }
+
+            File.WriteAllBytes(lower, [4, 5, 6]);
+            Environment.SetEnvironmentVariable("SHARPEMU_AMPR_INDEX_CACHE", cacheDir);
+
+            var normalizedRoot = Path.GetFullPath(root);
+            var expectedUpper = Path.Combine(normalizedRoot, "data", "ASSET.bin");
+            var expectedLower = Path.Combine(normalizedRoot, "data", "asset.bin");
+
+            // Fresh tree walk, which also writes the on-disk index cache.
+            AmprFileRegistry.ClearForTests();
+            AmprFileRegistry.EnsureApp0Indexed(root);
+            AssertResolves(expectedUpper, expectedLower);
+
+            // Second boot: served from the cache the walk just wrote.
+            AmprFileRegistry.ClearForTests();
+            AmprFileRegistry.EnsureApp0Indexed(root);
+            AssertResolves(expectedUpper, expectedLower);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("SHARPEMU_AMPR_INDEX_CACHE", previousCacheDir);
+            AmprFileRegistry.ClearForTests();
+            TryDeleteDirectory(cacheDir);
+            TryDeleteDirectory(root);
+        }
+
+        static void AssertResolves(string expectedUpper, string expectedLower)
+        {
+            Assert.True(
+                AmprFileRegistry.TryGetHostPath(
+                    AmprFileRegistry.ComputeFileId("$/data/ASSET.bin"), out var actualUpper),
+                "data/ASSET.bin is missing from the app0 index.");
+            Assert.True(
+                AmprFileRegistry.TryGetHostPath(
+                    AmprFileRegistry.ComputeFileId("$/data/asset.bin"), out var actualLower),
+                "data/asset.bin is missing from the app0 index.");
+            Assert.Equal(expectedUpper, actualUpper);
+            Assert.Equal(expectedLower, actualLower);
+        }
+    }
+
+    private static void TryDeleteDirectory(string path)
+    {
+        try
+        {
+            Directory.Delete(path, recursive: true);
+        }
+        catch (Exception)
+        {
+            // Temp cleanup is best-effort.
+        }
+    }
+
     private static uint FnvUtf8(string text)
     {
         const uint offset = 2166136261;

tests/SharpEmu.Libs.Tests/Ampr/AmprWriteAddressTests.cs

@@ -8,6 +8,7 @@ using Xunit;
 
 namespace SharpEmu.Libs.Tests.Ampr;
 
+[Collection("AmprFileRegistry")]
 public sealed class AmprWriteAddressTests
 {
     [Fact]

tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs

@@ -9,6 +9,7 @@ using Xunit;
 
 namespace SharpEmu.Libs.Tests.Ampr;
 
+[Collection("AmprFileRegistry")]
 public sealed class AprStreamingContractTests
 {
     [Fact]