Improve performance in cases of small or no diff updates

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Fixed
 
+- [Significant performance improvements](https://github.com/kyleve/Listable/pull/179) for list updates which contain either no changes, or only in-place updates to existing items and sections. In many cases, these updates will now be 80% faster. This change also improves performance for other types of changes such as insertions, removals, or moves, but not to the same degree.
+
 ### Added
 
 - [Added additional layout configuration options](https://github.com/kyleve/Listable/pull/173/): `headerToFirstSectionSpacing` and `lastSectionToFooterSpacing` now let you control the spacing between the list header and content, and the content and the list footer.

Debugging and Logging/SignpostLoggerTests.swift

@@ -0,0 +1,22 @@
+//
+//  SignpostLoggerTests.swift
+//  Listable-Unit-Tests
+//
+//  Created by Kyle Van Essen on 6/30/20.
+//
+
+import XCTest
+@testable import Listable
+
+
+class SignpostLoggerTests : XCTestCase {
+
+    func test_isLoggingEnabled_true_in_debug()
+    {
+        /// Test to validate that no one has accidentally committed disabling `isLoggingEnabled` in `DEBUG`.
+
+        #if DEBUG
+        XCTAssertEqual(true, SignpostLogger.isLoggingEnabled)
+        #endif
+    }
+}

Demo/Sources/Demos/Demo Screens/AutoScrollingViewController.swift

@@ -41,7 +41,7 @@ final class AutoScrollingViewController : UIViewController
 
     @objc private func addItem()
     {
-        let last = items.last?.identifier.toAny
+        let last = items.last?.identifier
 
         items.append(BottomPinnedItem(text: "Item \(items.count)"))
 

Demo/Sources/Demos/XcodePreviewDemo.swift

@@ -9,6 +9,7 @@
 import SwiftUI
 import BlueprintUICommonControls
 import BlueprintLists
+import Listable
 
 
 fileprivate struct XcodePreviewDemoContent : BlueprintItemContent, Equatable
@@ -83,6 +84,7 @@ fileprivate struct XcodePreviewDemoContent : BlueprintItemContent, Equatable
     }
 }
 
+#if DEBUG && canImport(SwiftUI) && !arch(i386) && !arch(arm)
 
 @available(iOS 13.0, *)
 struct ElementPreview : PreviewProvider {
@@ -94,3 +96,5 @@ struct ElementPreview : PreviewProvider {
         )
     }
 }
+
+#endif

Listable/Sources/Debugging and Logging/SignpostLogger.swift

@@ -49,13 +49,29 @@ struct SignpostLoggingInfo {
 ///
 /// Resources
 /// ---------
-///  WWDC: https://developer.apple.com/videos/play/wwdc2018/405/
+///  WWDC 2018: https://developer.apple.com/videos/play/wwdc2018/405/
+///  WWDC 2019: https://developer.apple.com/wwdc20/10168
 ///  Swift By Sundell: https://www.swiftbysundell.com/wwdc2018/getting-started-with-signposts/
 ///
 struct SignpostLogger {
-
+
+    #if DEBUG
+    /// You may temporarily set this param to `false` to disable os_signpost logging,
+    /// for example if debugging performance in Instruments.app.
+    ///
+    /// Note that tests will fail while this is set to `false` in `DEBUG`, to ensure
+    /// this is not accidentally commited as `false`.
+    static let isLoggingEnabled = true
+    #else
+    static let isLoggingEnabled = false
+    #endif
+
     static func log<Output>(log : OSLog, name: StaticString, for loggable : SignpostLoggable? = nil, _ output : () -> Output) -> Output
     {
+        guard self.isLoggingEnabled else {
+            return output()
+        }
+
         self.log(.begin, log: log, name: name, for: loggable)
 
         let output = output()
@@ -67,6 +83,10 @@ struct SignpostLogger {
 
     static func log(_ type : EventType, log : OSLog, name: StaticString, for loggable : SignpostLoggable? = nil)
     {
+        guard self.isLoggingEnabled else {
+            return
+        }
+
         if #available(iOS 12.0, *) {
             if let loggable = loggable {
                 os_signpost(

Listable/Sources/Identifier.swift

@@ -8,17 +8,21 @@
 import Foundation
 
 
-public final class AnyIdentifier : Hashable, CustomDebugStringConvertible
+public class AnyIdentifier : Hashable, CustomDebugStringConvertible
 {
-    private let value : AnyHashable
+    private let representedType : ObjectIdentifier
+
+    fileprivate let value : AnyHashable
 
     private let hash : Int
 
-    public init<Represented>(_ value : Identifier<Represented>)
+    fileprivate init(type : ObjectIdentifier, value : AnyHashable)
     {
-        self.value = AnyHashable(value)
+        self.representedType = type
+        self.value = value
 
         var hasher = Hasher()
+        hasher.combine(self.representedType)
         hasher.combine(self.value)
         self.hash = hasher.finalize()
     }
@@ -27,7 +31,7 @@ public final class AnyIdentifier : Hashable, CustomDebugStringConvertible
 
     public static func == (lhs: AnyIdentifier, rhs: AnyIdentifier) -> Bool
     {
-        return lhs.hash == rhs.hash && lhs.value == rhs.value
+        return lhs.hash == rhs.hash && lhs.representedType == rhs.representedType && lhs.value == rhs.value
     }
 
     // MARK: Hashable
@@ -39,19 +43,14 @@ public final class AnyIdentifier : Hashable, CustomDebugStringConvertible
 
     // MARK: CustomDebugStringConvertible
 
-    public var debugDescription: String {
-        self.value.identifierContentString
+    public var debugDescription : String {
+        fatalError()
     }
 }
 
 
-public final class Identifier<Represented> : Hashable, CustomDebugStringConvertible
+public final class Identifier<Represented> : AnyIdentifier
 {
-    private let type : ObjectIdentifier
-    private let value : AnyHashable
-
-    private let hash : Int
-
     /// Identifier which identifies by the type of `Represented` only.
     /// If you have multiple of `Represented` within a list, it is recommended that
     /// you use `init(_ value:)` to provide a unique inner value.
@@ -62,36 +61,15 @@ public final class Identifier<Represented> : Hashable, CustomDebugStringConverti
 
     public init<Value:Hashable>(_ value : Value)
     {
-        self.value = AnyHashable(value)
-        self.type = ObjectIdentifier(Represented.self)
-
-        var hasher = Hasher()
-        hasher.combine(self.type)
-        hasher.combine(self.value)
-        self.hash = hasher.finalize()
-    }
-
-    public var toAny : AnyIdentifier {
-        AnyIdentifier(self)
-    }
-
-    // MARK: Equatable
-
-    public static func == (lhs: Identifier<Represented>, rhs: Identifier<Represented>) -> Bool
-    {
-        return lhs.hash == rhs.hash && lhs.type == rhs.type && lhs.value == rhs.value
-    }
-
-    // MARK: Hashable
-
-    public func hash(into hasher: inout Hasher)
-    {
-        hasher.combine(self.hash)
+        super.init(
+            type: ObjectIdentifier(Represented.self),
+            value: AnyHashable(value)
+        )
     }
 
     // MARK: CustomDebugStringConvertible
 
-    public var debugDescription: String {
+    public override var debugDescription : String {
         "Identifier<\(String(describing: Represented.self))>: \(self.value.identifierContentString)"
     }
 }