Allow registration on SSO only servers.

Stop using the homeserver from user defaults.

RiotSwiftUI/Modules/Authentication/Common/Service/MatrixSDK/AuthenticationService.swift

@@ -48,21 +48,14 @@ class AuthenticationService: NSObject {
     // MARK: - Setup
     
     override init() {
-        if let homeserverURL = URL(string: RiotSettings.shared.homeserverUrlString) {
-            // Use the same homeserver that was last used.
-            state = AuthenticationState(flow: .login, homeserverAddress: RiotSettings.shared.homeserverUrlString)
-            client = MXRestClient(homeServer: homeserverURL, unrecognizedCertificateHandler: nil)
-            
-        } else if let homeserverURL = URL(string: BuildSettings.serverConfigDefaultHomeserverUrlString) {
-            // Fall back to the default homeserver if the stored one is invalid.
-            state = AuthenticationState(flow: .login, homeserverAddress: BuildSettings.serverConfigDefaultHomeserverUrlString)
-            client = MXRestClient(homeServer: homeserverURL, unrecognizedCertificateHandler: nil)
-            
-        } else {
+        guard let homeserverURL = URL(string: BuildSettings.serverConfigDefaultHomeserverUrlString) else {
             MXLog.failure("[AuthenticationService]: Failed to create URL from default homeserver URL string.")
             fatalError("Invalid default homeserver URL string.")
         }
         
+        state = AuthenticationState(flow: .login, homeserverAddress: BuildSettings.serverConfigDefaultHomeserverUrlString)
+        client = MXRestClient(homeServer: homeserverURL, unrecognizedCertificateHandler: nil)
+        
         super.init()
     }
     
@@ -97,10 +90,6 @@ class AuthenticationService: NSObject {
         
         let loginFlows = try await loginFlow(for: homeserverAddress)
         
-        // Valid Homeserver, add it to the history.
-        // Note: we add what the user has input, as the data can contain a different value.
-        RiotSettings.shared.homeserverUrlString = homeserverAddress
-        
         state.homeserver = .init(address: loginFlows.homeserverAddress,
                                  addressFromUser: homeserverAddress,
                                  preferredLoginMode: loginFlows.loginMode,
@@ -110,9 +99,16 @@ class AuthenticationService: NSObject {
         self.loginWizard = loginWizard
         
         if flow == .registration {
-            let registrationWizard = RegistrationWizard(client: client)
-            state.homeserver.registrationFlow = try await registrationWizard.registrationFlow()
-            self.registrationWizard = registrationWizard
+            do {
+                let registrationWizard = RegistrationWizard(client: client)
+                state.homeserver.registrationFlow = try await registrationWizard.registrationFlow()
+                self.registrationWizard = registrationWizard
+            } catch {
+                guard state.homeserver.preferredLoginMode.hasSSO, error as? RegistrationError == .registrationDisabled else {
+                    throw error
+                }
+                // Continue without throwing when registration is disabled but SSO is available.
+            }
         }
         
         state.flow = flow

RiotSwiftUI/Modules/Authentication/Common/Service/MatrixSDK/RegistrationFlowHandling.swift

@@ -20,7 +20,7 @@ import Foundation
 /// A protocol with a default implementation that allows a coordinator to execute and handle registration flow steps.
 protocol RegistrationFlowHandling {
     var authenticationService: AuthenticationService { get }
-    var registrationWizard: RegistrationWizard { get }
+    var registrationWizard: RegistrationWizard? { get }
     @MainActor var completion: ((AuthenticationRegistrationCoordinatorResult) -> Void)? { get }
     
     /// Executes a registration step using the `RegistrationWizard` to complete any additional steps automatically.
@@ -31,6 +31,11 @@ protocol RegistrationFlowHandling {
 @MainActor extension RegistrationFlowHandling {
     func executeRegistrationStep(step: @escaping (RegistrationWizard) async throws -> RegistrationResult) -> Task<Void, Error> {
         return Task {
+            guard let registrationWizard = registrationWizard else {
+                MXLog.failure("[RegistrationFlowHandling] executeRegistrationStep: The registration wizard is nil.")
+                return
+            }
+            
             do {
                 let result = try await step(registrationWizard)
                 

RiotSwiftUI/Modules/Authentication/Common/Service/MatrixSDK/RegistrationWizard.swift

@@ -74,7 +74,15 @@ class RegistrationWizard {
     /// See `AuthenticationService.getFallbackUrl`
     func registrationFlow() async throws -> RegistrationResult {
         let parameters = RegistrationParameters()
-        return try await performRegistrationRequest(parameters: parameters)
+        
+        do {
+            let result = try await performRegistrationRequest(parameters: parameters)
+            return result
+        } catch {
+            // Map M_FORBIDDEN into a registration error.
+            guard let mxError = MXError(nsError: error), mxError.errcode == kMXErrCodeStringForbidden else { throw error }
+            throw RegistrationError.registrationDisabled
+        }
     }
 
     /// Can be call to check is the desired username is available for registration on the current homeserver.