Use CaseIterable from Xcode 10. (#2484)

Now that Apple requires Xcode 10.1+ to submit to the App Store, we
can package the Zip file using Xcode 10.1.

Author: ryanwilson

ZipBuilder/Sources/ZipBuilder/FrameworkBuilder.swift

@@ -17,7 +17,7 @@
 import Foundation
 
 /// Different architectures to build frameworks for.
-private enum Architecture: String {
+private enum Architecture: String, CaseIterable {
   /// The target platform that the framework is built for.
   enum TargetPlatform: String {
     case device = "iphoneos"
@@ -48,11 +48,6 @@ private enum Architecture: String {
     case .i386, .x86_64: return .simulator
     }
   }
-
-  // TODO: Once we default to Swift 4.2 (in Xcode 10) we can conform to "CaseIterable" protocol to
-  //       automatically generate this method.
-  /// All the architectures to parse.
-  public static func allCases() -> [Architecture] { return [.arm64, .armv7, .i386, .x86_64] }
 }
 
 /// A structure to build a .framework in a given project directory.
@@ -356,7 +351,7 @@ struct FrameworkBuilder {
     // TODO: Pass in supported architectures here, for those that don't support individual
     // architectures (MLKit).
     var thinArchives = [URL]()
-    for arch in Architecture.allCases() {
+    for arch in Architecture.allCases {
       let buildDir = projectDir.appendingPathComponent(arch.rawValue)
       let thinArchive = buildThin(framework: framework,
                                   arch: arch,

ZipBuilder/Sources/ZipBuilder/LaunchArgs.swift

@@ -38,7 +38,7 @@ extension FileManager: FileChecker {}
 /// `-myKey myValue`.
 struct LaunchArgs {
   /// Keys associated with the launch args. See `Usage` for descriptions of each flag.
-  private enum Key: String {
+  private enum Key: String, CaseIterable {
     case cacheEnabled
     case customSpecRepos
     case coreDiagnosticsDir
@@ -76,21 +76,6 @@ struct LaunchArgs {
         return "A flag to run `pod repo update` before building the zip file."
       }
     }
-
-    // TODO: Once we default to Swift 4.2 (in Xcode 10) we can conform to "CaseIterable" protocol to
-    //       automatically generate this method.
-    /// All the subspecs to parse.
-    static func allCases() -> [Key] {
-      return [.cacheEnabled,
-              .coreDiagnosticsDir,
-              .customSpecRepos,
-              .deleteCache,
-              .existingVersions,
-              .outputDir,
-              .releasingSDKs,
-              .templateDir,
-              .updatePodRepo]
-    }
   }
 
   /// A file URL to a textproto with the contents of a `ZipBuilder_FirebaseSDKs` object. Used to
@@ -232,7 +217,7 @@ struct LaunchArgs {
 
     // Loop over all the possible keys and print their description.
     print("Usage: `swift run ZipBuilder [ARGS]` where args are:")
-    for option in Key.allCases() {
+    for option in Key.allCases {
       print("""
       -\(option.rawValue) <VALUE>
           \(option.usage)

ZipBuilder/Sources/ZipBuilder/Subspec.swift

@@ -18,7 +18,7 @@ import Foundation
 
 // TODO: Auto generate this list from the Firebase.podspec, probably with a script.
 /// All the subspecs available in the Firebase pod.
-public enum Subspec: String {
+public enum Subspec: String, CaseIterable {
   case abTesting = "ABTesting"
   case adMob = "AdMob"
   case analytics = "Analytics"
@@ -55,39 +55,6 @@ public enum Subspec: String {
     }
   }
 
-  // TODO: Once we default to Swift 4.2 (in Xcode 10) we can conform to "CaseIterable" protocol to
-  //       automatically generate this method.
-  /// All the subspecs to parse.
-  public static func allCases() -> [Subspec] {
-    return [
-      .abTesting,
-      .adMob,
-      .analytics,
-      .auth,
-      .core,
-      .crash,
-      .database,
-      .dynamicLinks,
-      .firestore,
-      .functions,
-      .inAppMessaging,
-      .inAppMessagingDisplay,
-      .invites,
-      .messaging,
-      .mlModelInterpreter,
-      .mlNaturalLanguage,
-      .mlNLLanguageID,
-      .mlVision,
-      .mlVisionBarcodeModel,
-      .mlVisionFaceModel,
-      .mlVisionLabelModel,
-      .mlVisionTextModel,
-      .performance,
-      .remoteConfig,
-      .storage,
-    ]
-  }
-
   /// The minimum supported iOS version.
   public func minSupportedIOSVersion() -> OperatingSystemVersion {
     // All ML pods have a minimum iOS version of 9.0.

ZipBuilder/Sources/ZipBuilder/ZipBuilder.swift

@@ -180,7 +180,7 @@ struct ZipBuilder {
 
     // Break the `subspecsToInstall` into a variable since it's helpful when debugging non-cache
     // builds to just install a subset: `[.core, .analytics, .storage, .firestore]` for example.
-    let subspecsToInstall = Subspec.allCases()
+    let subspecsToInstall = Subspec.allCases
 
     // We need to install all the subpsecs in order to get every single framework that we'll need
     // for the zip file. We can't install each one individually since some pods depend on different