base red: the app server link's launcher and route move to CmuxNextCloudCredentials (tip arch red from ccb777fdde80)

Packages/macOS/CmuxNext/Sources/CmuxNextApp/Cloud/CloudService.swift

@@ -239,27 +239,13 @@ final class CloudService {
         // The app server link: this Mac's `cmux link`, or with `CMUX_NEXT_CLOUD_NATIVE_LINK=1` the Native
         // device route (#28947) with `cmux link` as its fallback when Native does not start.
         let linkBuild = LaunchIdentity.current().build
-        let cmuxLink = CloudLinkLauncher.forApp(build: linkBuild, relay: relay)
-        let launcher: (any CloudLinkLaunching)?
-        if configuration.linkSource != .appServer {
-            launcher = nil
-            linkRoute = { "legacy" }
-        } else if CloudNativeFirstLauncher.choice() == .link {
-            launcher = cmuxLink
-            linkRoute = { "link" }
-        } else if let native = CloudNativeRouteHolder.forApp(identity: identity, auth: auth, paths: paths,
-                                                             build: linkBuild, deviceName: Self.deviceName) {
-            let logger = Logger(subsystem: "com.cmuxterm.app.next", category: "app.cloud")
-            let first = CloudNativeFirstLauncher(native: native, link: cmuxLink) { error in
-                logger.error("cloud.link native route failed, using cmux link: \(String(describing: error), privacy: .public)")
-            }
-            launcher = first
-            linkRoute = { first.route }
-        } else {
-            launcher = cmuxLink
-            linkRoute = { "link (native asked; no Native route holder for this app)" }
+        let appServerLink = CloudAppServerLink(appServer: configuration.linkSource == .appServer, link: CloudLinkLauncher.forApp(build: linkBuild, relay: relay),
+            native: { CloudNativeRouteHolder.forApp(identity: identity, auth: auth, paths: paths, build: linkBuild, deviceName: Self.deviceName) }) { error in
+            Logger(subsystem: "com.cmuxterm.app.next", category: "app.cloud")
+                .error("cloud.link native route failed, using cmux link: \(String(describing: error), privacy: .public)")
         }
-        link = CloudLinkLifecycle(launcher: launcher, installID: { [identity] in await identity.installID() },
+        linkRoute = appServerLink.route
+        link = CloudLinkLifecycle(launcher: appServerLink.launcher, installID: { [identity] in await identity.installID() },
                                   connection: { [machines] in machines.local.connection })
         binary = try? DaemonLauncher.resolveBinary(bundle: .main, environment: ProcessInfo.processInfo.environment)
         move.cli = binary

Packages/macOS/CmuxNext/Sources/CmuxNextCloudCredentials/CloudAppServerLink.swift

@@ -0,0 +1,28 @@
+public import CmuxNextDaemon
+
+/// The app server link's launcher, and its route as launched for `cloud.machines`' `link_route`: `legacy`,
+/// `link`, or the Native-first launcher's (``CloudNativeFirstLauncher/route``).
+@MainActor
+public struct CloudAppServerLink {
+    /// Nil for the legacy link (no app server link).
+    public let launcher: (any CloudLinkLaunching)?
+    public let route: @MainActor () -> String
+
+    /// The launcher of an `appServer` link source: this Mac's `cmux link` (`link`), or with `choice` `.native`
+    /// (`CMUX_NEXT_CLOUD_NATIVE_LINK=1`, #28947) the Native device route `native()` makes, with `link` as its
+    /// fallback when Native does not start (`onFallback` says why). `native` runs only for that choice.
+    public init(appServer: Bool, link: (any CloudLinkLaunching)?,
+                choice: CloudNativeFirstLauncher.Choice = CloudNativeFirstLauncher.choice(),
+                native: () -> (any CloudLinkLaunching)?, onFallback: @escaping (any Error) -> Void) {
+        if !appServer {
+            (launcher, route) = (nil, { "legacy" })
+        } else if choice == .link {
+            (launcher, route) = (link, { "link" })
+        } else if let native = native() {
+            let first = CloudNativeFirstLauncher(native: native, link: link, onFallback: onFallback)
+            (launcher, route) = (first, { first.route })
+        } else {
+            (launcher, route) = (link, { "link (native asked; no Native route holder for this app)" })
+        }
+    }
+}

Packages/macOS/CmuxNext/Tests/CmuxNextAppTests/CloudNativeFirstLauncherTests.swift

@@ -50,6 +50,28 @@ struct CloudNativeFirstLauncherTests {
         #expect(try await launcher.ensure(install: "i").status == "native")
     }
 
+    /// `cloud.machines`' `link_route` (#32494): the launcher each link source and choice gets, and its route.
+    @Test func theAppServerLinkReportsTheRouteItLaunched() async throws {
+        let link = FakeLauncher(status: "link")
+        var asked = 0
+        let legacy = CloudAppServerLink(appServer: false, link: link, choice: .native, native: { asked += 1; return nil }) { _ in }
+        #expect(legacy.launcher == nil && legacy.route() == "legacy")
+        let cmuxLink = CloudAppServerLink(appServer: true, link: link, choice: .link, native: { asked += 1; return nil }) { _ in }
+        #expect(cmuxLink.launcher as? FakeLauncher === link && cmuxLink.route() == "link")
+        #expect(asked == 0, "the Native route holder was made for a choice that does not use it")
+        let noHolder = CloudAppServerLink(appServer: true, link: link, choice: .native, native: { asked += 1; return nil }) { _ in }
+        #expect(asked == 1 && noHolder.launcher as? FakeLauncher === link)
+        #expect(noHolder.route() == "link (native asked; no Native route holder for this app)")
+
+        let native = FakeLauncher(status: "native", failure: NativeDeviceEnrollmentError.refused(400))
+        var reasons = 0
+        let first = CloudAppServerLink(appServer: true, link: link, choice: .native, native: { native }) { _ in reasons += 1 }
+        #expect(first.launcher is CloudNativeFirstLauncher && first.route() == "native")
+        #expect(try await first.launcher?.ensure(install: "i").status == "link")
+        #expect(reasons == 1)
+        #expect(first.route() == "link (native failed: \(NativeDeviceEnrollmentError.refused(400)))")
+    }
+
     @Test func signedOutIsNotARouteFailure() async {
         let native = FakeLauncher(status: "native", failure: NativeDeviceEnrollmentError.signedOut)
         let link = FakeLauncher(status: "link")