feat(ios/engine): temp package cleanup

ios/engine/KMEI/KeymanEngine/Classes/KeymanPackage.swift

@@ -26,6 +26,8 @@ public class KeymanPackage {
   public let sourceFolder: URL
   public let id: String
   internal let metadata: KMPMetadata
+
+  // Used to denote Packages pending installation; referenced by ResourceFileManager.
   internal let isTemp: Bool
 
   internal init(metadata: KMPMetadata, folder: URL) {

ios/engine/KMEI/KeymanEngine/Classes/Migrations.swift

@@ -518,12 +518,7 @@ public enum Migrations {
 
       allLocalPackages = kmpFiles.compactMap { file in
         let filePath = cachedKMPsDirectory.appendingPathComponent(file)
-        do {
-          return try ResourceFileManager.shared.prepareKMPInstall(from: filePath)
-        } catch {
-          log.error("Error occurred when processing existing packages during cloud -> KMP migration: \(String(describing: error))")
-          return nil as KeymanPackage?
-        }
+        return ResourceFileManager.shared.getPackageInfo(for: filePath)
       }
     } catch {
       log.error("Could not check contents of Documents directory for resource-migration assist")

ios/engine/KMEI/KeymanEngine/Classes/Resource Management/PackageInstallViewController.swift

@@ -55,6 +55,14 @@ public class PackageInstallViewController: UIViewController {
 
   @objc func cancelBtnHandler() {
     dismiss(animated: true, completion: nil)
+    // Note:  package.sourceFolder is a temporary directory, as set by preparePackageInstall.
+    do {
+      try FileManager.default.removeItem(at: package.sourceFolder)
+    } catch {
+      // Our attempt to clean up the temporarily-extracted contents failed.
+      // At least we extracted to a temp (cache) folder; we'll let iOS
+      // handle it, then.
+    }
   }
 
   @objc func installBtnHandler() {

ios/engine/KMEI/KeymanEngine/Classes/Resource Management/ResourceFileManager.swift

@@ -138,6 +138,23 @@ public class ResourceFileManager {
     }
   }
 
+  /**
+   * Similar to `preparePackageInstall`, but the resuting `KeymanPackage` cannot be used for installation.  Use when you
+   * want information about a package's contents when not immediately looking to install its resources.
+   */
+  public func getPackageInfo(for url: URL) -> KeymanPackage? {
+    // Facilitates clean retrieval of a package's metadata by temporarily extracting
+    // its contents just long enough to parse the kmp.json.
+    do {
+      let package = try self.prepareKMPInstall(from: url)
+      try FileManager.default.removeItem(at: package.sourceFolder)
+      return package
+    } catch {
+      log.error("Error occurred attempting to extract metadata for KMP at \(String(describing: url)): \(String(describing: error))")
+      return nil
+    }
+  }
+
   public func promptPackageInstall(of package: KeymanPackage,
                                    in rootVC: UIViewController,
                                    isCustom: Bool,