Handle helper installation errors

Xcodes/Backend/AppState+Install.swift

@@ -303,32 +303,29 @@ extension AppState {
     }
 
     func enableDeveloperMode() -> AnyPublisher<Void, Error> {
-        if helperInstallState == .notInstalled {
-            installHelper()
-        }
-
-        return Current.helper.devToolsSecurityEnable()
+        installHelperIfNecessary()
+            .flatMap {
+                Current.helper.devToolsSecurityEnable()
+            }
             .flatMap {
                 Current.helper.addStaffToDevelopersGroup()
             }
             .eraseToAnyPublisher()
     }
 
     func approveLicense(for xcode: InstalledXcode) -> AnyPublisher<Void, Error> {
-        if helperInstallState == .notInstalled {
-            installHelper()
-        }
-
-        return Current.helper.acceptXcodeLicense(xcode.path.string)
+        installHelperIfNecessary()
+            .flatMap {
+                Current.helper.acceptXcodeLicense(xcode.path.string)
+            }
             .eraseToAnyPublisher()
     }
 
     func installComponents(for xcode: InstalledXcode) -> AnyPublisher<Void, Swift.Error> {
-        if helperInstallState == .notInstalled {
-            installHelper()
-        }
-
-        return Current.helper.runFirstLaunch(xcode.path.string)
+        installHelperIfNecessary()
+            .flatMap {
+                Current.helper.runFirstLaunch(xcode.path.string)
+            }
             .flatMap {
                 Current.shell.getUserCacheDir().map { $0.out }
                     .combineLatest(

Xcodes/Backend/AppState.swift

@@ -203,9 +203,29 @@ class AppState: ObservableObject {
 
     // MARK: - Helper
 
-    func installHelper() {
-        Current.helper.install()
-        checkIfHelperIsInstalled()
+    func installHelperIfNecessary() {
+        installHelperIfNecessary()
+            .sink(
+                receiveCompletion: { [unowned self] completion in
+                    if case let .failure(error) = completion {
+                        self.error = error
+                    }
+                }, 
+                receiveValue: {}
+            )
+            .store(in: &cancellables)
+    }
+
+    func installHelperIfNecessary() -> AnyPublisher<Void, Error> {
+        Result {
+            if helperInstallState == .notInstalled {
+                try Current.helper.install()
+                checkIfHelperIsInstalled()
+            }
+        }
+        .publisher
+        .subscribe(on: DispatchQueue.main)
+        .eraseToAnyPublisher()
     }
 
     private func checkIfHelperIsInstalled() {
@@ -320,16 +340,15 @@ class AppState: ObservableObject {
     }
 
     func select(id: Xcode.ID) {
-        if helperInstallState == .notInstalled {
-            installHelper()
-        }
-
         guard 
             let installedXcode = Current.files.installedXcodes(Path.root/"Applications").first(where: { $0.version == id }),
             selectPublisher == nil
         else { return }
 
-        selectPublisher = HelperClient().switchXcodePath(installedXcode.path.string)
+        selectPublisher = installHelperIfNecessary()
+            .flatMap {
+                Current.helper.switchXcodePath(installedXcode.path.string)
+            }
             .flatMap { [unowned self] _ in
                 self.updateSelectedXcodePath()
             }

Xcodes/Backend/Environment.swift

@@ -237,7 +237,7 @@ public struct Defaults {
 
 private let helperClient = HelperClient()
 public struct Helper {
-    var install: () -> Void = helperClient.install
+    var install: () throws -> Void = helperClient.install
     var checkIfLatestHelperIsInstalled: () -> AnyPublisher<Bool, Never> = helperClient.checkIfLatestHelperIsInstalled
     var getVersion: () -> AnyPublisher<String, Error> = helperClient.getVersion
     var switchXcodePath: (_ absolutePath: String) -> AnyPublisher<Void, Error> = helperClient.switchXcodePath

Xcodes/Backend/HelperClient.swift

@@ -307,7 +307,7 @@ final class HelperClient {
     // MARK: - Install
     // From https://github.com/securing/SimpleXPCApp/
 
-    func install() {
+    func install() throws {
         Logger.helperClient.info(#function)
 
         var authItem = kSMRightBlessPrivilegedHelper.withCString { name in
@@ -329,13 +329,19 @@ final class HelperClient {
             Logger.helperClient.info("\(#function): Finished installation")
         } catch {
             Logger.helperClient.error("\(#function): \(error.localizedDescription)")
+
+            throw error
         }
     }
 
     private func executeAuthorizationFunction(_ authorizationFunction: () -> (OSStatus) ) throws {
         let osStatus = authorizationFunction()
         guard osStatus == errAuthorizationSuccess else {
-            throw HelperClientError.message(String(describing: SecCopyErrorMessageString(osStatus, nil)))
+            if let message = SecCopyErrorMessageString(osStatus, nil) {
+                throw HelperClientError.message(String(message as NSString))
+            } else {
+                throw HelperClientError.message("Unknown error")
+            }
         }
     }
 

Xcodes/Frontend/Preferences/AdvancedPreferencePane.swift

@@ -55,7 +55,7 @@ struct AdvancedPreferencePane: View {
                         HStack {
                             Text("Helper is not installed")
                             Button("Install helper") {
-                                appState.installHelper()
+                                appState.installHelperIfNecessary()
                             }
                         }
                     }