Refactor FXIOS-10205 [Swiftlint] Enable implicitly_unwrapped_optional…

… rule but keep it disabled for test files using nested Swiftlint configurations (#24031)

* Enable implicitly_unwrapped_optional rule in swiftlint configuration

* Disable rule for test files using swiftlint nested configuration

* Disable rule for focus-ios using swiftlint nested config

* Resolve implicitly_unwrapped_optional violation in SampleComponentLibraryApp

* Resolve implicitly_unwrapped_optional violations in SampleBrowser

.swiftlint.yml

@@ -86,6 +86,7 @@ only_rules: # Only enforce these rules, ignore all others
   - accessibility_trait_for_button
   - force_cast
   - closure_body_length
+  - implicitly_unwrapped_optional
 
 # These rules were originally opted into. Disabling for now to get
 # Swiftlint up and running.

BrowserKit/Tests/.swiftlint.yml

@@ -0,0 +1,9 @@
+# Swiftlint configuration overloads that will be applied to all files
+# in this folder and all its children recursively, unless another
+# nested configuration takes over.
+# https://github.com/realm/SwiftLint#nested-configurations.
+
+disabled_rules:
+  # Many test use implicitly unwrapped optional properties that 
+  # initialized in setUp and reset in tearDown.
+  - implicitly_unwrapped_optional

SampleBrowser/SampleBrowser/Engine/EngineProvider.swift

@@ -7,15 +7,15 @@ import WebEngine
 
 struct EngineProvider {
     // We only have one session in the SampleBrowser
-    private(set) var session: EngineSession?
+    private(set) var session: EngineSession
     let view: EngineView
 
-    init(engine: Engine = WKEngine.factory(),
-         sessionDependencies: EngineSessionDependencies? = nil) {
+    init?(engine: Engine = WKEngine.factory(),
+          sessionDependencies: EngineSessionDependencies? = nil) {
         do {
             session = try engine.createSession(dependencies: sessionDependencies)
         } catch {
-            session = nil
+            return nil
         }
 
         view = engine.createView()

SampleBrowser/SampleBrowser/SceneDelegate.swift

@@ -8,15 +8,15 @@ import WebEngine
 
 class SceneDelegate: UIResponder, UIWindowSceneDelegate {
     var window: UIWindow?
-    var engineProvider: EngineProvider = {
+    var engineProvider: EngineProvider? = {
         let dependencies = EngineSessionDependencies(telemetryProxy: TelemetryHandler())
         return EngineProvider(sessionDependencies: dependencies)
     }()
 
     func scene(_ scene: UIScene,
                willConnectTo session: UISceneSession,
                options connectionOptions: UIScene.ConnectionOptions) {
-        guard let windowScene = (scene as? UIWindowScene) else { return }
+        guard let windowScene = (scene as? UIWindowScene), let engineProvider else { return }
         let windowUUID = UUID()
         let baseViewController = RootViewController(engineProvider: engineProvider, windowUUID: windowUUID)
         window = UIWindow(windowScene: windowScene)

SampleBrowser/SampleBrowser/UI/Browser/BrowserViewController.swift

@@ -21,7 +21,7 @@ class BrowserViewController: UIViewController,
                              FindInPageHelperDelegate {
     weak var navigationDelegate: NavigationDelegate?
     private lazy var progressView: UIProgressView = .build { _ in }
-    private var engineSession: EngineSession!
+    private var engineSession: EngineSession
     private var engineView: EngineView
     private let urlFormatter: URLFormatter
 
@@ -203,7 +203,7 @@ class BrowserViewController: UIViewController,
         guard let url = linkURL else { return nil }
 
         let previewProvider: UIContextMenuContentPreviewProvider = {
-            let previewEngineProvider = EngineProvider()
+            guard let previewEngineProvider = EngineProvider() else { return nil }
             let previewVC = BrowserViewController(engineProvider: previewEngineProvider)
             previewVC.engineSession.load(url: url.absoluteString)
             return previewVC

SampleBrowser/SampleBrowser/UI/Suggestion/SuggestionViewController.swift

@@ -10,7 +10,7 @@ protocol SuggestionViewControllerDelegate: AnyObject {
 
 class SuggestionViewController: UIViewController, UITableViewDelegate {
     private var tableView: UITableView
-    private var dataSource: SuggestionDataSource!
+    private var dataSource: SuggestionDataSource?
     private weak var delegate: SuggestionViewControllerDelegate?
 
     private var gradientLayer: CAGradientLayer?
@@ -87,14 +87,14 @@ class SuggestionViewController: UIViewController, UITableViewDelegate {
 
     func updateUI(for suggestions: [String]) {
         tableView.isHidden = suggestions.isEmpty
-        dataSource.suggestions = suggestions
+        dataSource?.suggestions = suggestions
         tableView.reloadData()
     }
 
     // MARK: - UITableViewDelegate
 
     func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
-        let term = dataSource.suggestions[indexPath.row]
+        guard let term = dataSource?.suggestions[indexPath.row] else { return }
         delegate?.tapOnSuggestion(term: term)
     }
 }

SampleComponentLibraryApp/SampleComponentLibraryApp/BottomSheet/BottomSheetChildViewController.swift

@@ -25,8 +25,6 @@ class BottomSheetChildViewController: UIViewController, BottomSheetChild, Themea
         label.numberOfLines = 0
     }
 
-    private var heightConstraint: NSLayoutConstraint!
-
     init(themeManager: ThemeManager = AppContainer.shared.resolve()) {
         self.themeManager = themeManager
         super.init(nibName: nil, bundle: nil)

firefox-ios/firefox-ios-tests/Tests/.swiftlint.yml

@@ -0,0 +1,9 @@
+# Swiftlint configuration overloads that will be applied to all files
+# in this folder and all its children recursively, unless another
+# nested configuration takes over.
+# https://github.com/realm/SwiftLint#nested-configurations.
+
+disabled_rules:
+  # Many test use implicitly unwrapped optional properties that 
+  # initialized in setUp and reset in tearDown.
+  - implicitly_unwrapped_optional

focus-ios/.swiftlint.yml

@@ -14,4 +14,5 @@ disabled_rules:
   - attributes
   - trailing_whitespace
   - vertical_whitespace
+  - implicitly_unwrapped_optional