Avoid using Combine FlatMap, that leaks memory when Fail is returned (#…

…32)
teufelaudio · Jan 25, 2022 · 21010b4 · 21010b4
1 parent a2a0775
commit 21010b4
Show file tree

Hide file tree

Showing 6 changed files with 32 additions and 18 deletions.
diff --git a/Sources/FoundationExtensions/Combine/Publisher+FlatMapResult.swift b/Sources/FoundationExtensions/Combine/Publisher+FlatMapResult.swift
@@ -13,10 +13,9 @@ import Foundation
 @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 extension Publisher {
     public func flatMapResult<T>(
-        maxPublishers: Subscribers.Demand = .unlimited,
         _ transform: @escaping (Self.Output) -> Result<T, Failure>
-    ) -> Publishers.FlatMap<Result<T, Failure>.Publisher, Self> {
-        flatMap(maxPublishers: maxPublishers) { value in
+    ) -> Publishers.FlatMapLatest<Self, Result<T, Failure>.Publisher> {
+        flatMapLatest { value in
             transform(value).publisher
         }
     }

diff --git a/Sources/FoundationExtensions/Combine/Publishers+PrependLatest.swift b/Sources/FoundationExtensions/Combine/Publishers+PrependLatest.swift
@@ -13,7 +13,7 @@ import Combine
 @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 extension Publishers.CombineLatest {
     public func prependLatest<P: Publisher>(_ publisher: P) -> AnyPublisher<Output, Failure> where P.Output == Output, P.Failure == Failure {
-        publisher.flatMap { left, right in
+        publisher.flatMapLatest { left, right in
             Publishers.CombineLatest(
                 self.a.prepend(left),
                 self.b.prepend(right)

diff --git a/Sources/FoundationExtensions/Promise/NonEmptyPublisher.swift b/Sources/FoundationExtensions/Promise/NonEmptyPublisher.swift
@@ -34,7 +34,7 @@ public struct NonEmptyPublisher<Upstream: Publisher>: Publisher {
         upstream
             .map(EmptyStream.someValue)
             .replaceEmpty(with: EmptyStream.empty)
-            .flatMap { valueType -> AnyPublisher<Output, Failure> in
+            .flatMapLatest { valueType -> AnyPublisher<Output, Failure> in
                 switch valueType {
                 case .empty:
                     switch fallback() {

diff --git a/Sources/FoundationExtensions/Promise/Promise+HTTPStatusCode.swift b/Sources/FoundationExtensions/Promise/Promise+HTTPStatusCode.swift
@@ -4,14 +4,14 @@ import Foundation
 @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 extension Publishers.Promise where Success == (data: Data, response: URLResponse), Failure == URLError {
     public func validStatusCode() -> Publishers.Promise<Void, URLError> {
-        flatMap { _, response -> Publishers.Promise<Void, URLError> in
+        flatMapResult { _, response -> Result<Void, URLError> in
             guard let httpResponse = response as? HTTPURLResponse else {
-                return Publishers.Promise(error: URLError(.badServerResponse))
+                return .failure(URLError(.badServerResponse))
             }
 
             return (200..<400) ~= httpResponse.statusCode
-                ? Publishers.Promise(value: ())
-                : Publishers.Promise(error: URLError(.badServerResponse))
+                ? .success(())
+                : .failure(URLError(.badServerResponse))
         }
     }
 }
diff --git a/Sources/FoundationExtensions/Promise/PromiseType+DefaultOperators.swift b/Sources/FoundationExtensions/Promise/PromiseType+DefaultOperators.swift
@@ -63,19 +63,34 @@ extension PromiseType {
         Publishers.Promise { self.eraseToAnyPublisher().print(prefix, to: stream) }
     }
 
-    public func flatMapResult<T>(maxPublishers: Subscribers.Demand = .unlimited, _ transform: @escaping (Output) -> Result<T, Failure>) -> Publishers.Promise<T, Failure> {
-        Publishers.Promise { self.eraseToAnyPublisher().flatMapResult(maxPublishers: maxPublishers, transform) }
+    public func flatMapResult<T>(_ transform: @escaping (Output) -> Result<T, Failure>) -> Publishers.Promise<T, Failure> {
+        Publishers.Promise { self.eraseToAnyPublisher().flatMapResult(transform) }
     }
 
-    public func flatMap<O>(maxPublishers: Subscribers.Demand = .unlimited, _ transform: @escaping (Output) -> Publishers.Promise<O, Never>) -> Publishers.Promise<O, Failure> {
+    public func flatMap<O>(_ transform: @escaping (Output) -> Publishers.Promise<O, Never>) -> Publishers.Promise<O, Failure> {
+        Publishers.Promise { self.eraseToAnyPublisher().flatMapLatest { transform($0).setFailureType(to: Failure.self) } }
+    }
+
+    public func flatMap<O, E: Error>(_ transform: @escaping (Output) -> Publishers.Promise<O, E>) -> Publishers.Promise<O, E> where Failure == Never {
+        Publishers.Promise { self.eraseToAnyPublisher().setFailureType(to: E.self).flatMapLatest(transform) }
+    }
+
+    public func flatMap<O>(_ transform: @escaping (Output) -> Publishers.Promise<O, Failure>) -> Publishers.Promise<O, Failure> {
+        Publishers.Promise { self.eraseToAnyPublisher().flatMapLatest(transform) }
+    }
+
+    @available(*, deprecated, message: "Please use the function without providing maxPublishers, as the original Combine FlatMap may have some issues when returning error.")
+    public func flatMap<O>(maxPublishers: Subscribers.Demand, _ transform: @escaping (Output) -> Publishers.Promise<O, Never>) -> Publishers.Promise<O, Failure> {
         Publishers.Promise { self.eraseToAnyPublisher().flatMap(maxPublishers: maxPublishers) { transform($0).setFailureType(to: Failure.self) } }
     }
 
-    public func flatMap<O, E: Error>(maxPublishers: Subscribers.Demand = .unlimited, _ transform: @escaping (Output) -> Publishers.Promise<O, E>) -> Publishers.Promise<O, E> where Failure == Never {
+    @available(*, deprecated, message: "Please use the function without providing maxPublishers, as the original Combine FlatMap may have some issues when returning error.")
+    public func flatMap<O, E: Error>(maxPublishers: Subscribers.Demand, _ transform: @escaping (Output) -> Publishers.Promise<O, E>) -> Publishers.Promise<O, E> where Failure == Never {
         Publishers.Promise { self.eraseToAnyPublisher().setFailureType(to: E.self).flatMap(maxPublishers: maxPublishers, transform) }
     }
 
-    public func flatMap<O>(maxPublishers: Subscribers.Demand = .unlimited, _ transform: @escaping (Output) -> Publishers.Promise<O, Failure>) -> Publishers.Promise<O, Failure> {
+    @available(*, deprecated, message: "Please use the function without providing maxPublishers, as the original Combine FlatMap may have some issues when returning error.")
+    public func flatMap<O>(maxPublishers: Subscribers.Demand, _ transform: @escaping (Output) -> Publishers.Promise<O, Failure>) -> Publishers.Promise<O, Failure> {
         Publishers.Promise { self.eraseToAnyPublisher().flatMap(maxPublishers: maxPublishers, transform) }
     }
 

diff --git a/Sources/FoundationExtensions/Reader/Reader+Publisher.swift b/Sources/FoundationExtensions/Reader/Reader+Publisher.swift
@@ -28,18 +28,18 @@ extension Reader where Value: Publisher {
         mapValue { $0.map(transform).mapError(errorTransform).eraseToAnyPublisher() }
     }
 
-    public func flatMapPublisher<NewPublisher: Publisher>(
+    public func flatMapLatestPublisher<NewPublisher: Publisher>(
         _ transform: @escaping (Value.Output) -> NewPublisher
     ) -> Reader<Environment, AnyPublisher<NewPublisher.Output, Value.Failure>> where NewPublisher.Failure == Value.Failure {
-        mapValue { $0.flatMap { transform($0) }.eraseToAnyPublisher() }
+        mapValue { $0.flatMapLatest { transform($0) }.eraseToAnyPublisher() }
     }
 
-    public func flatMapPublisher<NewPublisher: Publisher>(
+    public func flatMapLatestPublisher<NewPublisher: Publisher>(
         _ transform: @escaping (Value.Output) -> Reader<Environment, NewPublisher>
     ) -> Reader<Environment, AnyPublisher<NewPublisher.Output, NewPublisher.Failure>> where Value: Publisher, Value.Failure == NewPublisher.Failure {
         flatMap { publisher -> Reader<Environment, AnyPublisher<NewPublisher.Output, NewPublisher.Failure>> in
             Reader<Environment, AnyPublisher<NewPublisher.Output, NewPublisher.Failure>> { env in
-                publisher.flatMap { value -> AnyPublisher<NewPublisher.Output, NewPublisher.Failure> in
+                publisher.flatMapLatest { value -> AnyPublisher<NewPublisher.Output, NewPublisher.Failure> in
                     transform(value).inject(env).eraseToAnyPublisher()
                 }.eraseToAnyPublisher()
             }