Ensure that duplicate Opts aren’t passed when starting a Caffeination

Author: aaplmath

Sources/CaffeineKit/Caffeination.swift

@@ -11,7 +11,10 @@ import Cocoa
 /// An instance of a sleep-prevention session.
 public class Caffeination {
 
-    /// An customization option for a `Caffeination`.
+    /**
+     A customization option for a `Caffeination`.
+     - Note: Any given `Caffeination` can be passed only **one** of each `Opt`. So, for instance, it is valid to pass a `.timed` and `.process` Opt; however, it is not possible to have two different `.process` Opts.
+     */
     public enum Opt {
         /// Prevents disk idle sleep.
         case disk
@@ -230,8 +233,7 @@ public class Caffeination {
         - safety: Whether to enable safety measures to ensure that no "zombie" `caffeinate` processes can outlive the current application. Set to `true` by default, which is recommended.
         - terminationHandler: A handler that will be called when the Caffeination stops. Will be set to `nil` if the parameter is not specified.
      */
-   public init(withOpts opts: [Opt] = Opt.defaults, safety: Bool = true, terminationHandler: ((Caffeination) -> Void)? = nil) {
-        // TODO: duplicate opt entries need to be disallowed because they result in unexpected behavior
+    public init(withOpts opts: [Opt] = Opt.defaults, safety: Bool = true, terminationHandler: ((Caffeination) -> Void)? = nil) {
         self.opts = opts
         if safety {
             self.interceptAppTermination = true
@@ -329,14 +331,20 @@ public class Caffeination {
         Logger.logLevel = level
     }
 
-    /// Ensures that the Caffeinate executable exists and that no Caffeination is already active.
+    /// Ensures that the Caffeinate executable exists, no Caffeination is already active, and no duplicate Opts have been passed to this Caffeination.
     private func preCaffeinateSafetyCheck() throws {
         guard isActive == false else {
             throw CaffeinationError.alreadyActive
         }
         guard Caffeination.caffeinateExists else {
             throw CaffeinationError.caffeinateNotFound
         }
+        let optsSorted = opts.sorted(by: { $0.argumentList[0] > $1.argumentList[0] })
+        for i in 1..<optsSorted.count {
+            if optsSorted[i - 1].argumentList[0] == optsSorted[i].argumentList[0] {
+                throw CaffeinationError.duplicateOpts
+            }
+        }
     }
 
     // Allows the termination handler to be mutated even after the process has started

Sources/CaffeineKit/Enums.swift

@@ -40,6 +40,9 @@ public enum CaffeinationError: Swift.Error {
 
     /// Thrown if an attempt is made to start a Caffeination on an already-active instance.
     case alreadyActive
+    
+    /// Thrown if duplicate options are passed to a Caffeination
+    case duplicateOpts
 }
 
 /// An error related to signal trapping.

Tests/CaffeineKitTests/CaffeineKitTests.swift

@@ -238,4 +238,21 @@ final class CaffeineKitTests: XCTestCase {
         let nilOpt = Caffeination.Opt.from([String(rand), "-t"])
         XCTAssert(nilOpt == nil)
     }
+    
+    func testDuplicateOptsThrows() {
+        let caf = Caffeination(withOpts: [.timed(2), .disk, .timed(4)])
+        do {
+            try caf.start()
+            XCTFail("Duplicate opts, so error should have been thrown")
+        } catch let e as CaffeinationError {
+            switch e {
+            case .duplicateOpts:
+                break
+            default:
+                XCTFail("Wrong error thrown for duplicate opts")
+            }
+        } catch {
+            XCTFail("Non-CaffeinationError thrown for duplicate opts")
+        }
+    }
 }