remove mutating properties from context.

client/ios/DivKit/DivBlockModelingContext.swift

@@ -13,8 +13,8 @@ import AppKit
 
 public struct DivBlockModelingContext {
   public let cardId: DivCardID
-  var cardLogId: String?
-  var parentDivStatePath: DivStatePath?
+  private(set) var cardLogId: String?
+  private(set) var parentDivStatePath: DivStatePath?
   let stateManager: DivStateManager
   public let blockStateStorage: DivBlockStateStorage
   let visibilityCounter: DivVisibilityCounting
@@ -30,9 +30,9 @@ public struct DivBlockModelingContext {
   let debugParams: DebugParams
   let scheduler: Scheduling
   let playerFactory: PlayerFactory?
-  var childrenA11yDescription: String?
+  private(set) var childrenA11yDescription: String?
   private(set) weak var parentScrollView: ScrollView?
-  public internal(set) var errorsStorage: DivErrorsStorage
+  public private(set) var errorsStorage: DivErrorsStorage
   private let persistentValuesStorage: DivPersistentValuesStorage
   let tooltipViewFactory: DivTooltipViewFactory?
   public let variablesStorage: DivVariablesStorage
@@ -40,20 +40,8 @@ public struct DivBlockModelingContext {
   private let variableValueProvider: (String) -> Any?
   private let functionsProvider: FunctionsProvider
   private let variableTracker: ExpressionResolver.VariableTracker
-
-  public internal(set) var parentPath: UIElementPath {
-    didSet {
-      expressionResolver = makeExpressionResolver(
-        variableValueProvider: variableValueProvider,
-        functionsProvider: functionsProvider,
-        parentPath: parentPath,
-        errorsStorage: errorsStorage,
-        variableTracker: variableTracker
-      )
-    }
-  }
-
-  var sizeModifier: DivSizeModifier?
+  public private(set) var parentPath: UIElementPath
+  private(set) var sizeModifier: DivSizeModifier?
 
   public init(
     cardId: DivCardID,
@@ -82,6 +70,85 @@ public struct DivBlockModelingContext {
     variableTracker: DivVariableTracker? = nil,
     persistentValuesStorage: DivPersistentValuesStorage? = nil,
     tooltipViewFactory: DivTooltipViewFactory? = nil
+  ) {
+    let variableTracker: ExpressionResolver.VariableTracker = { variables in
+      variableTracker?.onVariablesUsed(cardId: cardId, variables: variables)
+    }
+    var extensionsHandlersDictionary = [String: DivExtensionHandler]()
+    extensionHandlers.forEach {
+      let id = $0.id
+      if extensionsHandlersDictionary[id] != nil {
+        DivKitLogger.failure("Duplicate DivExtensionHandler for: \(id)")
+        return
+      }
+      extensionsHandlersDictionary[id] = $0
+    }
+    var stateInterceptorsDictionary = [String: DivStateInterceptor]()
+    stateInterceptors.forEach {
+      let id = $0.id
+      if stateInterceptorsDictionary[id] != nil {
+        DivKitLogger.failure("Duplicate DivStateInterceptor for: \(id)")
+        return
+      }
+      stateInterceptorsDictionary[id] = $0
+    }
+    self.init(
+      cardId: cardId,
+      cardLogId: cardLogId,
+      parentPath: parentPath,
+      parentDivStatePath: parentDivStatePath,
+      stateManager: stateManager,
+      blockStateStorage: blockStateStorage,
+      visibilityCounter: visibilityCounter,
+      lastVisibleBoundsCache: lastVisibleBoundsCache,
+      imageHolderFactory: imageHolderFactory,
+      highPriorityImageHolderFactory: highPriorityImageHolderFactory,
+      divCustomBlockFactory: divCustomBlockFactory,
+      fontProvider: fontProvider,
+      flagsInfo: flagsInfo,
+      extensionHandlers: extensionsHandlersDictionary,
+      stateInterceptors: stateInterceptorsDictionary,
+      variablesStorage: variablesStorage,
+      playerFactory: playerFactory,
+      debugParams: debugParams,
+      scheduler: scheduler,
+      childrenA11yDescription: childrenA11yDescription,
+      parentScrollView: parentScrollView,
+      errorsStorage: errorsStorage,
+      layoutDirection: layoutDirection,
+      variableTracker: variableTracker,
+      persistentValuesStorage: persistentValuesStorage,
+      tooltipViewFactory: tooltipViewFactory
+    )
+  }
+
+  init(
+    cardId: DivCardID,
+    cardLogId: String?,
+    parentPath: UIElementPath?,
+    parentDivStatePath: DivStatePath?,
+    stateManager: DivStateManager,
+    blockStateStorage: DivBlockStateStorage,
+    visibilityCounter: DivVisibilityCounting?,
+    lastVisibleBoundsCache: DivLastVisibleBoundsCache?,
+    imageHolderFactory: DivImageHolderFactory,
+    highPriorityImageHolderFactory: DivImageHolderFactory?,
+    divCustomBlockFactory: DivCustomBlockFactory?,
+    fontProvider: DivFontProvider?,
+    flagsInfo: DivFlagsInfo,
+    extensionHandlers: [String: DivExtensionHandler],
+    stateInterceptors: [String: DivStateInterceptor],
+    variablesStorage: DivVariablesStorage,
+    playerFactory: PlayerFactory?,
+    debugParams: DebugParams,
+    scheduler: Scheduling?,
+    childrenA11yDescription: String?,
+    parentScrollView: ScrollView?,
+    errorsStorage: DivErrorsStorage?,
+    layoutDirection: UserInterfaceLayoutDirection,
+    variableTracker: @escaping ExpressionResolver.VariableTracker,
+    persistentValuesStorage: DivPersistentValuesStorage?,
+    tooltipViewFactory: DivTooltipViewFactory?
   ) {
     self.cardId = cardId
     self.cardLogId = cardLogId
@@ -104,36 +171,13 @@ public struct DivBlockModelingContext {
     self.parentScrollView = parentScrollView
     self.errorsStorage = errorsStorage ?? DivErrorsStorage(errors: [])
     self.layoutDirection = layoutDirection
-    let variableTracker: ExpressionResolver.VariableTracker = { variables in
-      variableTracker?.onVariablesUsed(cardId: cardId, variables: variables)
-    }
     self.variableTracker = variableTracker
     let persistentValuesStorage = persistentValuesStorage ?? DivPersistentValuesStorage()
     self.persistentValuesStorage = persistentValuesStorage
     self.tooltipViewFactory = tooltipViewFactory
     self.variablesStorage = variablesStorage
-
-    var extensionsHandlersDictionary = [String: DivExtensionHandler]()
-    extensionHandlers.forEach {
-      let id = $0.id
-      if extensionsHandlersDictionary[id] != nil {
-        DivKitLogger.failure("Duplicate DivExtensionHandler for: \(id)")
-        return
-      }
-      extensionsHandlersDictionary[id] = $0
-    }
-    self.extensionHandlers = extensionsHandlersDictionary
-
-    var stateInterceptorsDictionary = [String: DivStateInterceptor]()
-    stateInterceptors.forEach {
-      let id = $0.id
-      if stateInterceptorsDictionary[id] != nil {
-        DivKitLogger.failure("Duplicate DivStateInterceptor for: \(id)")
-        return
-      }
-      stateInterceptorsDictionary[id] = $0
-    }
-    self.stateInterceptors = stateInterceptorsDictionary
+    self.extensionHandlers = extensionHandlers
+    self.stateInterceptors = stateInterceptors
 
     let variableValueProvider: (String) -> Any? = {
       variablesStorage.getVariableValue(
@@ -149,7 +193,7 @@ public struct DivBlockModelingContext {
       },
       persistentValuesStorage: persistentValuesStorage
     )
-    expressionResolver = makeExpressionResolver(
+    self.expressionResolver = makeExpressionResolver(
       variableValueProvider: variableValueProvider,
       functionsProvider: functionsProvider,
       parentPath: parentPath,
@@ -211,6 +255,47 @@ public struct DivBlockModelingContext {
   }
 }
 
+extension DivBlockModelingContext {
+  func modifying(
+    cardLogId: String? = nil,
+    parentPath: UIElementPath? = nil,
+    parentDivStatePath: DivStatePath? = nil,
+    errorsStorage: DivErrorsStorage? = nil,
+    sizeModifier: DivSizeModifier? = nil
+  ) -> Self {
+    let expressionResolver: ExpressionResolver
+    let parentPath = parentPath ?? self.parentPath
+    let errorsStorage = errorsStorage ?? self.errorsStorage
+    if parentPath == self.parentPath {
+      expressionResolver = self.expressionResolver
+    } else {
+      expressionResolver = makeExpressionResolver(
+        variableValueProvider: variableValueProvider,
+        functionsProvider: functionsProvider,
+        parentPath: parentPath,
+        errorsStorage: errorsStorage,
+        variableTracker: variableTracker
+      )
+    }
+    return modified(self) {
+      $0.cardLogId = cardLogId ?? self.cardLogId
+      $0.parentPath = parentPath
+      $0.parentDivStatePath = parentDivStatePath ?? self.parentDivStatePath
+      $0.errorsStorage = errorsStorage
+      $0.sizeModifier = sizeModifier ?? self.sizeModifier
+      $0.expressionResolver = expressionResolver
+    }
+  }
+
+  func modifying(
+    childrenA11yDescription: String?
+  ) -> Self {
+    modified(self) {
+      $0.childrenA11yDescription = childrenA11yDescription
+    }
+  }
+}
+
 private func makeExpressionResolver(
   variableValueProvider: @escaping AnyCalcExpression.ValueProvider,
   functionsProvider: FunctionsProvider,

client/ios/DivKit/Extensions/ArrayExtensions.swift

@@ -8,10 +8,10 @@ extension Array where Element == Div {
     mappedBy modificator: (Div, Block) throws -> T
   ) rethrows -> [T] {
     try iterativeFlatMap { div, index in
-      let itemContext = modified(context) {
-        $0.parentPath += index
-        $0.sizeModifier = sizeModifier
-      }
+      let itemContext = context.modifying(
+        parentPath: context.parentPath + index,
+        sizeModifier: sizeModifier
+      )
       let block: Block
       do {
         block = try modifyError({

client/ios/DivKit/Extensions/DivContainer/DivContainerExtensions.swift

@@ -7,9 +7,9 @@ extension DivContainer: DivBlockModeling {
   public func makeBlock(context: DivBlockModelingContext) throws -> Block {
     try applyBaseProperties(
       to: { try makeBaseBlock(context: context) },
-      context: modified(context) {
-        $0.childrenA11yDescription = resolveChildrenA11yDescription($0)
-      },
+      context: context.modifying(
+        childrenA11yDescription: resolveChildrenA11yDescription(context)
+      ),
       actionsHolder: self
     )
   }
@@ -17,11 +17,11 @@ extension DivContainer: DivBlockModeling {
   var nonNilItems: [Div] {
     items ?? []
   }
-  
+
   private func makeBaseBlock(context: DivBlockModelingContext) throws -> Block {
-    let childContext = modified(context) {
-      $0.parentPath = $0.parentPath + (id ?? DivContainer.type)
-    }
+    let childContext = context.modifying(
+      parentPath: context.parentPath + (id ?? DivContainer.type)
+    )
     let expressionResolver = context.expressionResolver
     let orientation = resolveOrientation(expressionResolver)
     switch orientation {
@@ -55,9 +55,9 @@ extension DivContainer: DivBlockModeling {
       vertical: resolveContentAlignmentVertical(expressionResolver).alignment
     )
 
-    let childrenContext = modified(context) {
-      $0.errorsStorage = DivErrorsStorage(errors: [])
-    }
+    let childrenContext = context.modifying(
+      errorsStorage: DivErrorsStorage(errors: [])
+    )
     let children = nonNilItems.makeBlocks(
       context: childrenContext,
       sizeModifier: DivContainerSizeModifier(
@@ -121,9 +121,9 @@ extension DivContainer: DivBlockModeling {
       uiLayoutDirection: context.layoutDirection
     )
 
-    let childrenContext = modified(context) {
-      $0.errorsStorage = DivErrorsStorage(errors: [])
-    }
+    let childrenContext = context.modifying(
+      errorsStorage: DivErrorsStorage(errors: [])
+    )
 
     // Before block's making we need to filter items and remove
     // what has "matchParent" for opposite directions

client/ios/DivKit/Extensions/DivData/DivDataExtensions.swift

@@ -20,11 +20,12 @@ extension DivData: DivBlockModeling {
     let stateId = String(state.stateId)
     let statePath = DivStatePath(rawValue: UIElementPath(stateId))
     let div = state.div
-    let divContext = modified(context) {
-      $0.cardLogId = $0.cardLogId ?? logId
-      $0.parentPath = $0.parentPath + stateId
-      $0.parentDivStatePath = statePath
-    }
+
+    let divContext = context.modifying(
+      cardLogId: logId,
+      parentPath: context.parentPath + stateId,
+      parentDivStatePath: statePath
+    )
 
     stateManager.updateBlockIdsWithStateChangeTransition(
       statePath: statePath,

client/ios/DivKit/Extensions/DivGallery/DivGalleryExtensions.swift

@@ -17,9 +17,7 @@ extension DivGallery: DivBlockModeling, DivGalleryProtocol {
   private func makeBaseBlock(context: DivBlockModelingContext) throws -> Block {
     let galleryPath = context.parentPath + (id ?? DivGallery.type)
     let expressionResolver = context.expressionResolver
-    let galleryContext = modified(context) {
-      $0.parentPath = galleryPath
-    }
+    let galleryContext = context.modifying(parentPath: galleryPath)
     let defaultAlignment = resolveCrossContentAlignment(expressionResolver)
       .blockAlignment
     let itemSpacing = resolveItemSpacing(expressionResolver)

client/ios/DivKit/Extensions/DivGallery/DivGalleryProtocol.swift

@@ -21,9 +21,7 @@ extension DivGalleryProtocol {
     scrollbar: GalleryViewModel.Scrollbar = .none
   ) throws -> GalleryViewModel {
     let expressionResolver = context.expressionResolver
-    let childrenContext = modified(context) {
-      $0.errorsStorage = DivErrorsStorage(errors: [])
-    }
+    let childrenContext = context.modifying(errorsStorage: DivErrorsStorage(errors: []))
     var children: [GalleryViewModel.Item] = items.makeBlocks(
       context: childrenContext,
       sizeModifier: DivGallerySizeModifier(

client/ios/DivKit/Extensions/DivGridExtensions.swift

@@ -12,16 +12,12 @@ extension DivGrid: DivBlockModeling {
 
   private func makeBaseBlock(context: DivBlockModelingContext) throws -> Block {
     let gridPath = context.parentPath + DivGrid.type
-    let gridContext = modified(context) {
-      $0.parentPath = gridPath
-    }
-    let gridItemsContext = modified(gridContext) {
-      $0.errorsStorage = DivErrorsStorage(errors: [])
-    }
+    let gridContext = context.modifying(parentPath: gridPath)
+    let gridItemsContext = gridContext.modifying(errorsStorage: DivErrorsStorage(errors: []))
     let gridItems = items.enumerated().compactMap { tuple in
-      let itemContext = modified(gridItemsContext) {
-        $0.parentPath = $0.parentPath + tuple.offset
-      }
+      let itemContext = gridItemsContext.modifying(
+        parentPath: gridItemsContext.parentPath + tuple.offset
+      )
       do {
         return try tuple.element.value.makeGridItem(
           context: itemContext

client/ios/DivKit/Extensions/DivPagerExtensions.swift

@@ -17,9 +17,7 @@ extension DivPager: DivBlockModeling, DivGalleryProtocol {
   private func makeBaseBlock(context: DivBlockModelingContext) throws -> Block {
     let pagerPath = context.parentPath + (id ?? DivPager.type)
     let expressionResolver = context.expressionResolver
-    let itemContext = modified(context) {
-      $0.parentPath = pagerPath
-    }
+    let itemContext = context.modifying(parentPath: pagerPath)
     let pagerModelPath = id.map {
       PagerPath(
         cardId: context.cardId.rawValue,

client/ios/DivKit/Extensions/DivStateExtensions.swift

@@ -148,10 +148,10 @@ extension DivBlockModelingContext {
     id: String,
     stateId: String
   ) -> DivBlockModelingContext {
-    modified(self) {
-      $0.parentPath = parentPath + id + stateId
-      $0.parentDivStatePath = parentDivStatePath + id + stateId
-    }
+    modifying(
+      parentPath: parentPath + id + stateId,
+      parentDivStatePath: parentDivStatePath + id + stateId
+    )
   }
 }
 

client/ios/DivKit/Extensions/DivTabsExtensions.swift

@@ -21,12 +21,8 @@ extension DivTabs: DivBlockModeling {
     context: DivBlockModelingContext,
     tabsPath: UIElementPath
   ) throws -> Block {
-    let tabsContext = modified(context) {
-      $0.parentPath = tabsPath
-    }
-    let tabsItemContext = modified(tabsContext) {
-      $0.errorsStorage = DivErrorsStorage(errors: [])
-    }
+    let tabsContext = context.modifying(parentPath: tabsPath)
+    let tabsItemContext = tabsContext.modifying(errorsStorage: DivErrorsStorage(errors: []))
     let tabs = items.iterativeFlatMap { item, index in
       do {
         return try item.makeTab(context: tabsItemContext, index: index)
@@ -192,8 +188,8 @@ extension Typo {
 
 extension DivTabs.Item {
   fileprivate func makeTab(context: DivBlockModelingContext, index: Int) throws -> Tab {
-    let tabContext = modified(context) { $0.parentPath = $0.parentPath + index }
-    let pageContext = modified(tabContext) { $0.parentPath += "page" }
+    let tabContext = context.modifying(parentPath: context.parentPath + index)
+    let pageContext = tabContext.modifying(parentPath: tabContext.parentPath + "page")
     let title = makeTitle(context: tabContext)
     let page = try div.value
       .makeBlock(context: pageContext)
@@ -202,9 +198,9 @@ extension DivTabs.Item {
   }
 
   private func makeTitle(context: DivBlockModelingContext) -> UILink {
-    let titleContext = modified(context) {
-      $0.parentPath += "title"
-    }
+    let titleContext = context.modifying(
+      parentPath: context.parentPath + "title"
+    )
     let action = titleClickAction?.uiAction(context: context)
     return UILink(
       text: resolveTitle(titleContext.expressionResolver) ?? "",

client/ios/DivKit/Extensions/DivTooltipExtensions.swift

@@ -58,9 +58,9 @@ extension Optional where Wrapped == [DivTooltip] {
     context: DivBlockModelingContext
   ) throws -> [BlockTooltip] {
     try self?.iterativeFlatMap { div, index in
-      let tooltipContext = modified(context) {
-        $0.parentPath = $0.parentPath + "tooltip" + index
-      }
+      let tooltipContext = context.modifying(
+        parentPath: context.parentPath + "tooltip" + index
+      )
       return try div.makeTooltip(context: tooltipContext)
     } ?? []
   }

client/ios/DivKit/Extensions/DivVideoExtensions.swift

@@ -43,9 +43,7 @@ extension DivVideo: DivBlockModeling {
     )
 
     let videoPath = context.parentPath + (id ?? DivVideo.type)
-    let videoContext = modified(context) {
-      $0.parentPath = videoPath
-    }
+    let videoContext = context.modifying(parentPath: videoPath)
 
     let state: VideoBlockViewState = videoContext.blockStateStorage
       .getState(videoContext.parentPath) ?? .init(state: autostart == true ? .playing : .paused)