fix: notify on new Xcode version identity, not array-count growth

Xcodes.xcodeproj/project.pbxproj

@@ -31,6 +31,7 @@
 		BDBAB7452B9FF55800694B0B /* TrailingIconLabelStyle.swift in Sources */ = {isa = PBXBuildFile; fileRef = BDBAB7442B9FF55800694B0B /* TrailingIconLabelStyle.swift */; };
 		CA11E7BA2598476C00D2EE1C /* XcodeCommands.swift in Sources */ = {isa = PBXBuildFile; fileRef = CA11E7B92598476C00D2EE1C /* XcodeCommands.swift */; };
 		CA2518EC25A7FF2B00F08414 /* AppStateUpdateTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = CA2518EB25A7FF2B00F08414 /* AppStateUpdateTests.swift */; };
+		14d2f5a1273f6c350cad4406 /* NewVersionNotificationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 884f01aed2f43048ab4d3323 /* NewVersionNotificationTests.swift */; };
 		CA378F992466567600A58CE0 /* AppState.swift in Sources */ = {isa = PBXBuildFile; fileRef = CA378F982466567600A58CE0 /* AppState.swift */; };
 		CA39711924495F0E00AFFB77 /* AppStoreButtonStyle.swift in Sources */ = {isa = PBXBuildFile; fileRef = CA39711824495F0E00AFFB77 /* AppStoreButtonStyle.swift */; };
 		CA42DD7325AEB04300BC0B0C /* Logger.swift in Sources */ = {isa = PBXBuildFile; fileRef = CA42DD7225AEB04300BC0B0C /* Logger.swift */; };
@@ -208,6 +209,7 @@
 		BDBAB7442B9FF55800694B0B /* TrailingIconLabelStyle.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TrailingIconLabelStyle.swift; sourceTree = "<group>"; };
 		CA11E7B92598476C00D2EE1C /* XcodeCommands.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = XcodeCommands.swift; sourceTree = "<group>"; };
 		CA2518EB25A7FF2B00F08414 /* AppStateUpdateTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppStateUpdateTests.swift; sourceTree = "<group>"; };
+		884f01aed2f43048ab4d3323 /* NewVersionNotificationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NewVersionNotificationTests.swift; sourceTree = "<group>"; };
 		CA378F982466567600A58CE0 /* AppState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppState.swift; sourceTree = "<group>"; };
 		CA39711824495F0E00AFFB77 /* AppStoreButtonStyle.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppStoreButtonStyle.swift; sourceTree = "<group>"; };
 		CA42DD7225AEB04300BC0B0C /* Logger.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Logger.swift; sourceTree = "<group>"; };
@@ -594,6 +596,7 @@
 				CAC281E6259FA45A00B8AB0B /* Environment+Mock.swift */,
 				CAD2E7B72449575100113D76 /* AppStateTests.swift */,
 				CA2518EB25A7FF2B00F08414 /* AppStateUpdateTests.swift */,
+				884f01aed2f43048ab4d3323 /* NewVersionNotificationTests.swift */,
 				CAD2E7B92449575100113D76 /* Info.plist */,
 			);
 			path = XcodesTests;
@@ -970,6 +973,7 @@
 				CAC281E7259FA45A00B8AB0B /* Environment+Mock.swift in Sources */,
 				CAC281E2259FA44600B8AB0B /* Bundle+XcodesTests.swift in Sources */,
 				CA2518EC25A7FF2B00F08414 /* AppStateUpdateTests.swift in Sources */,
+				14d2f5a1273f6c350cad4406 /* NewVersionNotificationTests.swift in Sources */,
 				CAB3AB0E25BCA6C200BF1B04 /* AppStateTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

Xcodes/Backend/AppState.swift

@@ -43,7 +43,7 @@ class AppState: ObservableObject {
     @Published var authenticationState: AuthenticationState = .unauthenticated
     @Published var availableXcodes: [AvailableXcode] = [] {
         willSet {
-            if newValue.count > availableXcodes.count && availableXcodes.count != 0 {
+            if !Self.newlyAvailableXcodes(oldXcodes: availableXcodes, newXcodes: newValue).isEmpty {
                 Current.notificationManager.scheduleNotification(title: localizeString("Notification.NewXcodeVersion.Title"), body: localizeString("Notification.NewXcodeVersion.Body"), category: .normal)
             }
             updateAllXcodes(
@@ -56,6 +56,17 @@ class AppState: ObservableObject {
             autoInstallIfNeeded()
         }
     }
+
+    /// Returns the `AvailableXcode`s in `newXcodes` whose `xcodeID` was not present in `oldXcodes`.
+    ///
+    /// Empty when `oldXcodes` is empty, so the initial load (empty -> populated) is NOT treated
+    /// as "a new version since you last looked".
+    static func newlyAvailableXcodes(oldXcodes: [AvailableXcode], newXcodes: [AvailableXcode]) -> [AvailableXcode] {
+        guard !oldXcodes.isEmpty else { return [] }
+        let oldIDs = Set(oldXcodes.map(\.xcodeID))
+        return newXcodes.filter { !oldIDs.contains($0.xcodeID) }
+    }
+
     @Published var allXcodes: [Xcode] = []
     @Published var selectedXcodePath: String? {
         willSet {

XcodesTests/NewVersionNotificationTests.swift

@@ -0,0 +1,145 @@
+import Version
+import XcodesKit
+@testable import Xcodes
+import XCTest
+
+/// Regression tests for the "New Xcode version available" notification trigger.
+///
+/// The decision to notify is extracted into the pure helper
+/// `AppState.newlyAvailableXcodes(oldXcodes:newXcodes:)` and asserted directly here.
+/// No notification spying and no `Current = .mock` are required: the helper is the single
+/// source of truth that the `availableXcodes.willSet` predicate consults.
+@MainActor
+final class NewVersionNotificationTests: XCTestCase {
+    // MARK: - Fixtures
+
+    /// Builds an `AvailableXcode` for `version` with a distinct download URL, mirroring the
+    /// construction style in `AppStateUpdateTests.swift` (`Version("0.0.0")!`, three components).
+    /// `architectures` defaults to `nil`.
+    private func makeAvailableXcode(
+        version: String,
+        architectures: [Architecture]? = nil,
+        urlSuffix: String = ""
+    ) -> AvailableXcode {
+        AvailableXcode(
+            version: Version(version)!,
+            url: URL(string: "https://example.com/Xcode-\(version)-\(urlSuffix).xip")!,
+            filename: "Xcode-\(version)-\(urlSuffix).xip",
+            releaseDate: nil,
+            architectures: architectures
+        )
+    }
+
+    /// The set of stable identities (`xcodeID`) for the given available Xcodes — an
+    /// order-independent comparison keyed on version + architecture, not array position.
+    private func identities(_ xcodes: [AvailableXcode]) -> Set<XcodeID> {
+        Set(xcodes.map(\.xcodeID))
+    }
+
+    // MARK: - Initial-load suppression
+
+    func testInitialLoadDoesNotNotify() {
+        // First population (empty -> populated) is the initial cache load, NOT "a new version
+        // since you last looked", so the result must be empty even though the array grew.
+        let old: [AvailableXcode] = []
+        let new = [makeAvailableXcode(version: "15.0.0")]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertTrue(result.isEmpty, "Initial population must not be treated as a new version")
+    }
+
+    // MARK: - True positive — one genuinely new version
+
+    func testGenuinelyNewVersionIsReported() {
+        let existingA = makeAvailableXcode(version: "15.0.0")
+        let existingB = makeAvailableXcode(version: "15.1.0")
+        let added = makeAvailableXcode(version: "16.0.0")
+        let old = [existingA, existingB]
+        let new = [existingA, existingB, added]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertEqual(identities(result), [added.xcodeID])
+    }
+
+    // MARK: - FALSE NEGATIVE (the bug) — new version added AND old version removed, count unchanged
+
+    func testNewVersionAddedAndOldRemovedIsReported() {
+        // The OLD count-based predicate saw "no growth" (2 -> 2) here and MISSED version C.
+        // A data source can drop an obsolete beta row the same refresh it adds the new one.
+        let existing = makeAvailableXcode(version: "15.1.0")
+        let removed = makeAvailableXcode(version: "15.0.0")
+        let added = makeAvailableXcode(version: "16.0.0")
+        let old = [removed, existing]
+        let new = [existing, added]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertEqual(identities(result), [added.xcodeID], "A genuinely new version must be reported even when the count is unchanged")
+    }
+
+    // MARK: - FALSE NEGATIVE variant — a new version appears while the list shrinks
+
+    func testNewVersionReportedEvenWhenListShrinks() {
+        // A genuinely new version can appear even when the overall count DECREASES: a data source
+        // prunes older rows the same refresh it surfaces the newest (3 -> 2 here). The OLD
+        // count-based predicate saw "no growth" and MISSED D; the identity-based helper reports it.
+        let droppedA = makeAvailableXcode(version: "15.0.0")
+        let droppedB = makeAvailableXcode(version: "15.1.0")
+        let kept = makeAvailableXcode(version: "16.0.0")
+        let added = makeAvailableXcode(version: "17.0.0")
+        let old = [droppedA, droppedB, kept]
+        let new = [kept, added]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertEqual(identities(result), [added.xcodeID], "A new version must be reported even when the list shrinks")
+    }
+
+    // MARK: - FALSE POSITIVE (the bug) — count grows with NO new identity
+
+    func testDuplicateIdentityIsNotNew() {
+        // The OLD count-based predicate FIRED here (1 -> 2); the fixed helper correctly does not.
+        // The feed returns a row whose xcodeID was already present (a duplicate, same version).
+        let present = makeAvailableXcode(version: "15.0.0")
+        let duplicate = makeAvailableXcode(version: "15.0.0", urlSuffix: "duplicate") // same version -> same xcodeID
+        let old = [present]
+        let new = [present, duplicate]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertTrue(result.isEmpty, "A duplicate of an existing xcodeID must not be treated as new")
+    }
+
+    // MARK: - Identical list
+
+    func testIdenticalListIsNotNew() {
+        let a = makeAvailableXcode(version: "15.0.0")
+        let b = makeAvailableXcode(version: "15.1.0")
+        let old = [a, b]
+        let new = [a, b]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertTrue(result.isEmpty)
+    }
+
+    // MARK: - Identity is version + architecture, not version alone
+
+    func testSameVersionDifferentArchitectureIsDistinctIdentity() {
+        // Two AvailableXcodes with the same version but different architectures have DIFFERENT
+        // xcodeIDs (XcodeID.id = version.description + architectures), so an Apple-Silicon-only
+        // release is distinct from a Universal release of the same version.
+        let universal: [Architecture] = [.arm64, .x86_64]
+        let appleSilicon: [Architecture] = [.arm64]
+        let universalRelease = makeAvailableXcode(version: "15.0.0", architectures: universal)
+        let appleSiliconRelease = makeAvailableXcode(version: "15.0.0", architectures: appleSilicon)
+        let old = [universalRelease]
+        let new = [universalRelease, appleSiliconRelease]
+
+        let result = AppState.newlyAvailableXcodes(oldXcodes: old, newXcodes: new)
+
+        XCTAssertEqual(identities(result), [appleSiliconRelease.xcodeID])
+    }
+}