Native Builder: DiffKey and Differ Procol by wlan0 · Pull Request #482 · apple/container

wlan0 · 2025-08-11T08:18:04Z

This PR introduces the Differ with methods:

// Differ protocol
func diff(base: Snapshot?, target: Snapshot) async throws -> Descriptor
func apply(descriptor: Descriptor, to base: Snapshot?) async throws -> Snapshot

It also introduces DiffKey, which is a MerkeTree based key for fast diff computations between two dirs

Sources/NativeBuilder/ContainerBuildSnapshotter/Differ.swift

Sources/NativeBuilder/ContainerBuildSnapshotter/DiffKey.swift

Tests/NativeBuilderTests/ContainerBuildSnapshotterTests/BinaryPathTests.swift

katiewasnothere · 2025-08-12T16:49:26Z

Tests/NativeBuilderTests/ContainerBuildSnapshotterTests/BinaryPathTests.swift

+        // Alternative test: ensure original path with valid UTF-8 round-trips correctly
+        let utf8Path = BinaryPath(string: "/usr/local/bin")
+        let utf8Data = try encoder.encode(utf8Path)
+        let utf8Decoded = try decoder.decode(BinaryPath.self, from: utf8Data)
+        #expect(utf8Path == utf8Decoded)


I think this is covered already in CodableWithValidUTF8

katiewasnothere · 2025-08-12T17:02:56Z

Tests/NativeBuilderTests/ContainerBuildSnapshotterTests/BinaryPathTests.swift

+    @Test func PathWithMultipleSlashes() {
+        let path = BinaryPath(string: "//usr///local//bin//")
+        let components = path.components
+        #expect(components.count == 3)
+        #expect(components[0].stringValue == "usr")
+        #expect(components[1].stringValue == "local")
+        #expect(components[2].stringValue == "bin")
+    }


I think this is already covered in PathComponents

katiewasnothere

A couple minor comments on the tests, otherwise LGTM

wlan0 requested review from crosbymichael and katiewasnothere August 11, 2025 08:18