[WIP] Mergeable theme from multiple files with hot reloading

Example/AppDelegate.swift

@@ -19,7 +19,8 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
 
         let url = URL(fileURLWithPath: #file).deletingLastPathComponent().appendingPathComponent("Style.yaml")
-        Stylist.shared.watch(url: url, animateChanges: true) { error in
+        let commonURL = URL(fileURLWithPath: #file).deletingLastPathComponent().appendingPathComponent("common.yml")
+        Stylist.shared.localMergeWatch(urls: [url, commonURL], animateChanges: true) { error in
             print("Error loading theme:\n\(error)")
         }
 

Example/common.yml

@@ -0,0 +1,5 @@
+variables:
+  primaryColor: F000FF
+styles:
+  largeFont:
+    font: title 1

Stylist.xcodeproj/project.pbxproj

@@ -12,6 +12,7 @@
 		52D6D9871BEFF229002C0205 /* Stylist.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 52D6D97C1BEFF229002C0205 /* Stylist.framework */; };
 		535BD3EF11C3878517DE35E8 /* Pods_Stylist_iOS.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = C186A7E7F661536D838BB3A0 /* Pods_Stylist_iOS.framework */; };
 		5CC7AE9BC309934F44DC1CE1 /* Pods_Stylist_tvOS_Tests.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9245472812F659E9F0E1973B /* Pods_Stylist_tvOS_Tests.framework */; };
+		829ED8B321F0B85F00A572A2 /* common.yml in Resources */ = {isa = PBXBuildFile; fileRef = 829ED8B221F0B85F00A572A2 /* common.yml */; };
 		8933C7851EB5B820000D00A4 /* Stylist.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7841EB5B820000D00A4 /* Stylist.swift */; };
 		8933C7881EB5B820000D00A4 /* Stylist.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7841EB5B820000D00A4 /* Stylist.swift */; };
 		8933C78E1EB5B82C000D00A4 /* StylistTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7891EB5B82A000D00A4 /* StylistTests.swift */; };
@@ -144,6 +145,7 @@
 		52D6D9F01BEFFFBE002C0205 /* Stylist.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Stylist.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		6E17AEA69B829DF29439909B /* Pods_Stylist_macOS_Tests.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_Stylist_macOS_Tests.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		77B3C447D96463E91495C16D /* Pods-Stylist-tvOS Tests.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Stylist-tvOS Tests.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Stylist-tvOS Tests/Pods-Stylist-tvOS Tests.debug.xcconfig"; sourceTree = "<group>"; };
+		829ED8B221F0B85F00A572A2 /* common.yml */ = {isa = PBXFileReference; lastKnownFileType = text; path = common.yml; sourceTree = "<group>"; };
 		859CDAE0E43DE87EEAF810A4 /* Pods-Stylist-macOS.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Stylist-macOS.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Stylist-macOS/Pods-Stylist-macOS.debug.xcconfig"; sourceTree = "<group>"; };
 		8933C7841EB5B820000D00A4 /* Stylist.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Stylist.swift; sourceTree = "<group>"; };
 		8933C7891EB5B82A000D00A4 /* StylistTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = StylistTests.swift; sourceTree = "<group>"; };
@@ -371,6 +373,7 @@
 				CC68ECD01F47A1540063AE1F /* Style.yaml */,
 				CC0B571E20B568140022E84E /* SectionView.swift */,
 				CC8C104A20C4F1D1001E593B /* ExampleViewController.swift */,
+				829ED8B221F0B85F00A572A2 /* common.yml */,
 			);
 			path = Example;
 			sourceTree = "<group>";
@@ -592,6 +595,7 @@
 				CC23851B1F478E8A00FB0073 /* LaunchScreen.storyboard in Resources */,
 				CC2385181F478E8A00FB0073 /* Assets.xcassets in Resources */,
 				CC2385161F478E8A00FB0073 /* Main.storyboard in Resources */,
+				829ED8B321F0B85F00A572A2 /* common.yml in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Stylist/Stylist.swift

@@ -187,6 +187,55 @@ public class Stylist {
         }
         return fileWatcher
     }
+
+    public func localMergeWatch(urls: [URL], animateChanges: Bool = true, parsingError: @escaping (ThemeError) -> Void) -> [FileWatcherProtocol] {
+        var fileWatchers = [FileWatcherProtocol]()
+
+        var hasLoaded = false
+        func updateThemes() {
+            let stylist = self
+            do {
+                let theme = try Theme(paths: urls.map { $0.path })
+                self.themes[urls.map { $0.path }.joined()] = theme
+                stylist.apply(theme: theme, animateChanges: animateChanges && hasLoaded)
+                hasLoaded = true
+            } catch let error as ThemeError {
+                parsingError(error)
+            } catch {
+                // unknown error occured
+            }
+        }
+
+        var fileUpdatedCount = 0
+        for url in urls {
+            let fileWatcher: FileWatcherProtocol
+            if url.isFileURL {
+                fileWatcher = FileWatcher.Local(path: url.path)
+            } else {
+                parsingError(ThemeError.remoteFileWatcherNotSupported)
+                break
+            }
+
+            do {
+                try fileWatcher.start { result in
+                    switch result {
+                    case .noChanges:
+                        break
+                    case .updated:
+                        fileUpdatedCount += 1
+                        if fileUpdatedCount >= urls.count {
+                            updateThemes()
+                        }
+                    }
+                }
+            } catch {
+                parsingError(ThemeError.notFound)
+            }
+
+            fileWatchers.append(fileWatcher)
+        }
+        return fileWatchers
+    }
 }
 
 struct WeakContainer<T: AnyObject> {

Stylist/Theme.swift

@@ -34,6 +34,33 @@ extension Theme {
         try self.init(data: data)
     }
 
+    public init(paths: [String]) throws {
+
+        var mergedDictionary = ["variables": [:], "styles": [:]]
+
+        for path in paths {
+            guard let data = FileManager.default.contents(atPath: path) else {
+                throw ThemeError.notFound
+            }
+            guard let string = String(data: data, encoding: .utf8) else {
+                throw ThemeError.decodingError
+            }
+            let yaml = try Yams.load(yaml: string)
+            guard let dictionary = yaml as? [String: Any] else {
+                throw ThemeError.decodingError
+            }
+            let variables: [String: Any] = dictionary["variables"] as? [String: Any] ?? [:]
+            let stylesDictionary = (dictionary["styles"] as? [String: Any]) ?? [:]
+
+            mergedDictionary["variables"] = (mergedDictionary["variables"] as? [String: Any])?.merging(variables, uniquingKeysWith: { (current, _) in current }) ?? [:]
+
+            mergedDictionary["styles"] = (mergedDictionary["styles"] as? [String: Any])?.merging(stylesDictionary, uniquingKeysWith: { (current, _) in current }) ?? [:]
+
+        }
+
+        try self.init(dictionary: mergedDictionary)
+    }
+
     public init(data: Data) throws {
         guard let string = String(data: data, encoding: .utf8) else {
             throw ThemeError.decodingError

Stylist/ThemeError.swift

@@ -19,4 +19,5 @@ public enum ThemeError: Error, Equatable {
     case invalidSizeClass(name: String, sizeClass: String)
     case invalidStyleContext(String)
     case invalidStyleSelector(String)
+    case remoteFileWatcherNotSupported
 }