Promise: make call to observe() a call finishing the promise chain

1 files changed, 9 insertions, 10 deletions

diff --git a/ios/MullvadVPN/Promise/Promise.swift b/ios/MullvadVPN/Promise/Promise.swift
index 91aa4ebdef..d1466e6dc6 100644
--- a/ios/MullvadVPN/Promise/Promise.swift
+++ b/ios/MullvadVPN/Promise/Promise.swift
@@ -45,17 +45,16 @@ final class Promise<Value> {
 
     deinit {
         switch state {
-        case .resolved, .cancelled:
+        case .resolved, .cancelled, .pending:
             break
-        case .pending, .executing:
+        case .executing:
             preconditionFailure("\(Self.self) is deallocated in \(state) state without being resolved or cancelled.")
         }
     }
 
     /// Observe the result of Promise.
     /// This method starts the promise execution if it hasn't started yet.
-    @discardableResult
-    func observe(_ receiveCompletion: @escaping (PromiseCompletion<Value>) -> Void) -> Self {
+    func observe(_ receiveCompletion: @escaping (PromiseCompletion<Value>) -> Void) {
         return lock.withCriticalBlock {
             switch state {
             case .resolved(let value, let queue):
@@ -72,7 +71,6 @@ final class Promise<Value> {
             case .executing:
                 observers.append(AnyPromiseObserver<Value>(receiveCompletion))
             }
-            return self
         }
     }
 
@@ -97,10 +95,10 @@ final class Promise<Value> {
     /// Trasform the value by producing a promise.
     func then<NewValue>(_ onResolve: @escaping (Value) -> Promise<NewValue>) -> Promise<NewValue> {
         return Promise<NewValue> { resolver in
-            _ = self.observe { completion in
+            self.observe { completion in
                 switch completion {
                 case .finished(let value):
-                    _ = onResolve(value).observe { completion in
+                    onResolve(value).observe { completion in
                         resolver.resolve(completion: completion)
                     }
                 case .cancelled:
@@ -113,7 +111,7 @@ final class Promise<Value> {
     /// Transform the value.
     func then<NewValue>(_ onResolve: @escaping (Value) -> NewValue) -> Promise<NewValue> {
         return Promise<NewValue> { resolver in
-            _ = self.observe { completion in
+            self.observe { completion in
                 resolver.resolve(completion: completion.map(onResolve))
             }
         }
@@ -159,7 +157,7 @@ final class Promise<Value> {
         defer { condition.unlock() }
 
         var returnValue: PromiseCompletion<Value>!
-        _ = observe { completion in
+        observe { completion in
             returnValue = completion
             condition.signal()
         }
@@ -221,6 +219,7 @@ final class PromiseCancellationToken {
 }
 
 struct PromiseResolver<Value> {
+    /// Target promise.
     private let promise: Promise<Value>
 
     /// Private initializer.
@@ -257,7 +256,7 @@ struct PromiseResolver<Value> {
 
     /// Set cancellation handler.
     func setCancelHandler(_ cancellation: @escaping () -> Void) {
-        _ = promise.observe { completion in
+        promise.observe { completion in
             switch completion {
             case .finished:
                 break