RCOCOA-1883: Add "Sync is not enabled for this App" as a catchable error in error handler

CHANGELOG.md

@@ -9,6 +9,8 @@ x.y.z Release notes (yyyy-MM-dd)
 * Code sign our published xcframeworks. By Apple's requirements, we should sign our release
   binaries so Xcode can validate it was signed by the same developer on every new version. 
   ([Apple](https://developer.apple.com/support/third-party-SDK-requirements/)).
+* Report sync warnings from the server such as sync being disabled server-side to the sync error handler.
+  ([#8020](https://github.com/realm/realm-swift/issues/8020)).
 
 ### Fixed
 * <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-swift/issues/????), since v?.?.?)

Realm/ObjectServerTests/RealmServer.swift

@@ -469,6 +469,7 @@
 public enum SyncMode {
     case pbs(String) // partition based
     case flx([String]) // flexible sync
+    case notSync
 }
 
 // MARK: RealmServer
@@ -484,7 +485,7 @@
     }
 
     /// Shared RealmServer. This class only needs to be initialized and torn down once per test suite run.
     @objc public static let shared = RealmServer()
 
     /// Log level for the server and mongo processes.
     public var logLevel = LogLevel.none
@@ -815,6 +816,10 @@
             }
         }
 
+        if case .notSync = syncMode {
+            return clientAppId
+        }
+
         app.secrets.post(on: group, [
             "name": "BackingDB_uri",
             "value": "mongodb://localhost:26000"
@@ -927,6 +932,8 @@
                     "delete": true
                 ]]
             ]).get()
+        default:
+            fatalError()
         }
         _ = try app.services[serviceId].config.patch(serviceConfig).get()
 
@@ -1011,6 +1018,10 @@
         return try createApp(syncMode: .pbs(partitionKeyType), types: types, persistent: persistent)
     }
 
+    @objc public func createNotSyncApp() throws -> AppId {
+        return try createApp(syncMode: .notSync, types: [], persistent: false)
+    }
+
     /// Delete all Apps created without `persistent: true`
     @objc func deleteApps() throws {
         for appId in appIds {
@@ -1028,10 +1039,7 @@
 
     // Retrieve Atlas App Services AppId with ClientAppId using the Admin API
     public func retrieveAppServerId(_ clientAppId: String) throws -> String {
-        guard let session = session else {
-            fatalError()
-        }
-
+        let session = try XCTUnwrap(session)
         let appsListInfo = try session.apps.get().get()
         guard let appsList = appsListInfo as? [[String: Any]] else {
             throw URLError(.badServerResponse)
@@ -1052,9 +1060,7 @@
     }
 
     public func retrieveSyncServiceId(appServerId: String) throws -> String {
-        guard let session = session else {
-            fatalError()
-        }
+        let session = try XCTUnwrap(session)
         let app = session.apps[appServerId]
         // Get all services
         guard let syncServices = try app.services.get().get() as? [[String: Any]] else {
@@ -1083,14 +1089,11 @@
         }
     }
 
-    public func isSyncEnabled(flexibleSync: Bool = false, appServerId: String, syncServiceId: String) throws -> Bool {
-        let configOption = flexibleSync ? "flexible_sync" : "sync"
-        guard let session = session else {
-            fatalError()
-        }
+    public func isSyncEnabled(appServerId: String, syncServiceId: String) throws -> Bool {
+        let session = try XCTUnwrap(session)
         let app = session.apps[appServerId]
         let response = try app.services[syncServiceId].config.get().get() as? [String: Any]
-        guard let syncInfo = response?[configOption] as? [String: Any] else {
+        guard let syncInfo = response?["flexible_sync"] as? [String: Any] else {
             return false
         }
         return syncInfo["state"] as? String == "enabled"
@@ -1113,28 +1116,23 @@
         return app.sync.config.put(["development_mode_enabled": true])
     }
 
-    public func disableSync(flexibleSync: Bool = false, appServerId: String, syncServiceId: String)
-            -> Result<Any?, Error> {
-        let configOption = flexibleSync ? "flexible_sync" : "sync"
-        guard let session = session else {
-            return .failure(URLError(.unknown))
-        }
+    public func disableSync(appServerId: String, syncServiceId: String) throws -> Any? {
+        let session = try XCTUnwrap(session)
         let app = session.apps[appServerId]
-        return app.services[syncServiceId].config.patch([configOption: ["state": ""]])
+        return app.services[syncServiceId].config.patch(["flexible_sync": ["state": ""]])
     }
 
-    public func enableSync(flexibleSync: Bool = false, appServerId: String, syncServiceId: String, syncServiceConfiguration: [String: Any]) -> Result<Any?, Error> {
-        let configOption = flexibleSync ? "flexible_sync" : "sync"
+    public func enableSync(appServerId: String, syncServiceId: String, syncServiceConfiguration: [String: Any]) -> Result<Any?, Error> {
         var syncConfig = syncServiceConfiguration
         guard let session = session else {
             return .failure(URLError(.unknown))
         }
         let app = session.apps[appServerId]
-        guard var syncInfo = syncConfig[configOption] as? [String: Any] else {
+        guard var syncInfo = syncConfig["flexible_sync"] as? [String: Any] else {
             return .failure(URLError(.unknown))
         }
         syncInfo["state"] = "enabled"
-        syncConfig[configOption] = syncInfo
+        syncConfig["flexible_sync"] = syncInfo
         return app.services[syncServiceId].config.patch(syncConfig)
     }
 
@@ -1258,7 +1256,7 @@
     }
 }
 
 extension String: Error {
 }
 
 #endif

Realm/ObjectServerTests/SwiftFlexibleSyncServerTests.swift

@@ -1186,6 +1186,20 @@ class SwiftFlexibleSyncTests: SwiftSyncTestCase {
         XCTAssertEqual(downloadCount.value, 0)
         XCTAssertEqual(uploadCount.value, 0)
     }
+
+    func testFlexibleSyncNotEnabledError() throws {
+        let appId = try RealmServer.shared.createNotSyncApp()
+        let app = app(id: appId)
+        let ex = expectation(description: "Waiting for error handler to be called...")
+        ex.assertForOverFulfill = false // error handler can legally be called multiple times
+        app.syncManager.errorHandler = { @Sendable (error, _) in
+            assertSyncError(error, .serverWarning, "Sync is not enabled for this app")
+            ex.fulfill()
+        }
+
+        _ = try Realm(configuration: configuration(app: app)) // Sync is disabled so we cannot use async open
+        wait(for: [ex], timeout: 10.0)
+    }
 }
 
 #endif // os(macOS)

Realm/RLMError.h

@@ -328,6 +328,14 @@ typedef RLM_ERROR_ENUM(NSInteger, RLMSyncError, RLMSyncErrorDomain) {
      Connecting to the server failed due to a TLS issue such as an invalid certificate.
      */
     RLMSyncErrorTLSHandshakeFailed = 13,
+    /**
+     The server has encountered an error that it wants the user to know about,
+     but is not necessarily fatal.
+
+     An error with this code may indicate that either sync is not enabled or it's trying to connect to
+     an edge server app.
+     */
+    RLMSyncErrorServerWarning = 14,
 };
 
 #pragma mark - RLMSyncAuthError

Realm/RLMError.mm

@@ -292,6 +292,8 @@ - (NSString *)reason {
                 errorCode = RLMSyncErrorClientResetError;
             else if (isSyncError)
                 errorCode = RLMSyncErrorClientSessionError;
+            else if (error.server_requests_action == realm::sync::ProtocolErrorInfo::Action::Warning)
+                errorCode = RLMSyncErrorServerWarning;
             else if (!error.is_fatal)
                 return nil;
             break;