[ASCellNode] Added indexPath property. (#2468)

* [ASCellNode] Added indexPath property.

* [ASCellNode] Cached the type of scrollView we're using in the node, and placed that logic in setScrollView.

* [ASCellNode] Removed table and collection view from indexPath, since they return the index paths from the view-space.

* Changed the logic for getting indexPath so that it works even when the cell is not displayed.

* [VerticalWithinHorizontalScrolling] Explicitally synthesized indexPath property.

AsyncDisplayKit/ASCellNode+Internal.h

@@ -63,6 +63,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, copy, nullable) NSIndexPath *cachedIndexPath;
 
+@property (weak, nonatomic, nullable) ASDisplayNode *owningNode;
+
 @end
 
 NS_ASSUME_NONNULL_END

AsyncDisplayKit/ASCellNode.h

@@ -108,6 +108,20 @@ typedef NS_ENUM(NSUInteger, ASCellNodeVisibilityEvent) {
  */
 @property (nonatomic, assign, getter=isHighlighted) BOOL highlighted;
 
+/**
+ * The current index path of this cell node, or @c nil if this node is
+ * not a valid item inside a table node or collection node.
+ *
+ * @note This property must be accessed on the main thread.
+ */
+@property (nonatomic, readonly, nullable) NSIndexPath *indexPath;
+
+/**
+ * The owning node (ASCollectionNode/ASTableNode) of this cell node, or @c nil if this node is
+ * not a valid item inside a table node or collection node or if those nodes are nil.
+ */
+@property (weak, nonatomic, readonly, nullable) ASDisplayNode *owningNode;
+
 /*
  * ASCellNode must forward touch events in order for UITableView and UICollectionView tap handling to work. Overriding
  * these methods (e.g. for highlighting) requires the super method be called.

AsyncDisplayKit/ASCellNode.mm

@@ -36,6 +36,12 @@
   ASDisplayNode *_viewControllerNode;
   UIViewController *_viewController;
   BOOL _suspendInteractionDelegate;
+
+  struct {
+    unsigned int isTableNode:1;
+    unsigned int isCollectionNode:1;
+  } _owningNodeType;
+
 }
 
 @end
@@ -186,6 +192,19 @@ static NSMutableSet *__cellClassesForVisibilityNotifications = nil; // See +init
   }
 }
 
+- (void)setOwningNode:(ASDisplayNode *)owningNode
+{
+  _owningNode = owningNode;
+
+  memset(&_owningNodeType, 0, sizeof(_owningNodeType));
+
+  if ([owningNode isKindOfClass:[ASTableNode class]]) {
+    _owningNodeType.isTableNode      = 1;
+  } else if ([owningNode isKindOfClass:[ASCollectionNode class]]) {
+    _owningNodeType.isCollectionNode = 1;
+  }
+}
+
 - (void)__setSelectedFromUIKit:(BOOL)selected;
 {
   if (selected != _selected) {
@@ -204,6 +223,19 @@ static NSMutableSet *__cellClassesForVisibilityNotifications = nil; // See +init
   }
 }
 
+- (NSIndexPath *)indexPath
+{
+  ASDisplayNodeAssertMainThread();
+
+  if (_owningNodeType.isTableNode) {
+    return [(ASTableNode *)self.owningNode indexPathForNode:self];
+  } else if (_owningNodeType.isCollectionNode) {
+    return [(ASCollectionNode *)self.owningNode indexPathForNode:self];
+  }
+
+  return nil;
+}
+
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wobjc-missing-super-calls"
 

AsyncDisplayKit/Details/ASCollectionDataController.mm

@@ -233,15 +233,14 @@
 
 - (void)_populateSupplementaryNodesOfKind:(NSString *)kind withSections:(NSIndexSet *)sections mutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts
 {
-  id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
+  __weak id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
-  ASEnvironmentTraitCollection environmentTraitCollection = environment.environmentTraitCollection;
 
   [sections enumerateRangesUsingBlock:^(NSRange range, BOOL * _Nonnull stop) {
     for (NSUInteger sec = range.location; sec < NSMaxRange(range); sec++) {
       NSUInteger itemCount = [self.collectionDataSource dataController:self supplementaryNodesOfKind:kind inSection:sec];
       for (NSUInteger i = 0; i < itemCount; i++) {
         NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:sec];
-        [self _populateSupplementaryNodeOfKind:kind atIndexPath:indexPath mutableContexts:contexts environmentTraitCollection:environmentTraitCollection];
+        [self _populateSupplementaryNodeOfKind:kind atIndexPath:indexPath mutableContexts:contexts environment:environment];
       }
     }
   }];
@@ -249,8 +248,7 @@
 
 - (void)_populateSupplementaryNodesOfKind:(NSString *)kind atIndexPaths:(NSArray<NSIndexPath *> *)indexPaths mutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts
 {
-  id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
+  __weak id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
-  ASEnvironmentTraitCollection environmentTraitCollection = environment.environmentTraitCollection;
 
   NSMutableIndexSet *sections = [NSMutableIndexSet indexSet];
   for (NSIndexPath *indexPath in indexPaths) {
@@ -262,13 +260,13 @@
       NSUInteger itemCount = [self.collectionDataSource dataController:self supplementaryNodesOfKind:kind inSection:sec];
       for (NSUInteger i = 0; i < itemCount; i++) {
         NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:sec];
-        [self _populateSupplementaryNodeOfKind:kind atIndexPath:indexPath mutableContexts:contexts environmentTraitCollection:environmentTraitCollection];
+        [self _populateSupplementaryNodeOfKind:kind atIndexPath:indexPath mutableContexts:contexts environment:environment];
       }
     }
   }];
 }
 
-- (void)_populateSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath mutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts environmentTraitCollection:(ASEnvironmentTraitCollection)environmentTraitCollection
+- (void)_populateSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath mutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts environment:(id<ASEnvironment>)environment
 {
   ASCellNodeBlock supplementaryCellBlock;
   if (_dataSourceImplementsSupplementaryNodeBlockOfKindAtIndexPath) {
@@ -283,7 +281,7 @@
                                                                         indexPath:indexPath
                                                          supplementaryElementKind:kind
                                                                   constrainedSize:constrainedSize
-                                                       environmentTraitCollection:environmentTraitCollection];
+                                                                      environment:environment];
   [contexts addObject:context];
 }
 

AsyncDisplayKit/Details/ASDataController.mm

@@ -476,8 +476,7 @@ NSString * const ASDataControllerRowNodeKind = @"_ASDataControllerRowNodeKind";
 {
   ASDisplayNodeAssertMainThread();
   
-  id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
+  __weak id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
-  ASEnvironmentTraitCollection environmentTraitCollection = environment.environmentTraitCollection;
   
   std::vector<NSInteger> counts = [self itemCountsFromDataSource];
   NSMutableArray<ASIndexedNodeContext *> *contexts = [NSMutableArray array];
@@ -493,7 +492,7 @@ NSString * const ASDataControllerRowNodeKind = @"_ASDataControllerRowNodeKind";
                                                                   indexPath:indexPath
                                                    supplementaryElementKind:nil
                                                             constrainedSize:constrainedSize
-                                                 environmentTraitCollection:environmentTraitCollection]];
+                                                                environment:environment]];
       }
     }
   }];
@@ -743,8 +742,7 @@ NSString * const ASDataControllerRowNodeKind = @"_ASDataControllerRowNodeKind";
   NSArray *sortedIndexPaths = [indexPaths sortedArrayUsingSelector:@selector(compare:)];
   NSMutableArray<ASIndexedNodeContext *> *contexts = [[NSMutableArray alloc] initWithCapacity:indexPaths.count];
 
-  id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
+  __weak id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
-  ASEnvironmentTraitCollection environmentTraitCollection = environment.environmentTraitCollection;
   
   for (NSIndexPath *indexPath in sortedIndexPaths) {
     ASCellNodeBlock nodeBlock = [_dataSource dataController:self nodeBlockAtIndexPath:indexPath];
@@ -753,7 +751,7 @@ NSString * const ASDataControllerRowNodeKind = @"_ASDataControllerRowNodeKind";
                                                               indexPath:indexPath
                                                supplementaryElementKind:nil
                                                         constrainedSize:constrainedSize
-                                             environmentTraitCollection:environmentTraitCollection]];
+                                                            environment:environment]];
   }
 
   ASInsertElementsIntoMultidimensionalArrayAtIndexPaths(_nodeContexts[ASDataControllerRowNodeKind], sortedIndexPaths, contexts);

AsyncDisplayKit/Details/ASIndexedNodeContext.h

@@ -24,13 +24,14 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly, strong) NSIndexPath *indexPath;
 @property (nonatomic, readonly, copy, nullable) NSString *supplementaryElementKind;
 @property (nonatomic, readonly, assign) ASSizeRange constrainedSize;
+@property (weak, nonatomic) id<ASEnvironment> environment;
 @property (nonatomic, readonly, assign) ASEnvironmentTraitCollection environmentTraitCollection;
 
 - (instancetype)initWithNodeBlock:(ASCellNodeBlock)nodeBlock
                         indexPath:(NSIndexPath *)indexPath
          supplementaryElementKind:(nullable NSString *)supplementaryElementKind
                   constrainedSize:(ASSizeRange)constrainedSize
-       environmentTraitCollection:(ASEnvironmentTraitCollection)environmentTraitCollection;
+                      environment:(id<ASEnvironment>)environment;
 
 /**
  * @return The node, running the node block if necessary. The node block will be discarded

AsyncDisplayKit/Details/ASIndexedNodeContext.mm

@@ -31,7 +31,7 @@
                         indexPath:(NSIndexPath *)indexPath
          supplementaryElementKind:(nullable NSString *)supplementaryElementKind
                   constrainedSize:(ASSizeRange)constrainedSize
-       environmentTraitCollection:(ASEnvironmentTraitCollection)environmentTraitCollection
+                      environment:(id<ASEnvironment>)environment
 {
   NSAssert(nodeBlock != nil && indexPath != nil, @"Node block and index path must not be nil");
   self = [super init];
@@ -40,7 +40,8 @@
     _indexPath = indexPath;
     _supplementaryElementKind = [supplementaryElementKind copy];
     _constrainedSize = constrainedSize;
-    _environmentTraitCollection = environmentTraitCollection;
+    _environment = environment;
+    _environmentTraitCollection = environment.environmentTraitCollection;
   }
   return self;
 }
@@ -57,6 +58,7 @@
     }
     node.cachedIndexPath = _indexPath;
     node.supplementaryElementKind = _supplementaryElementKind;
+    node.owningNode = (ASDisplayNode *)_environment;
     ASEnvironmentStatePropagateDown(node, _environmentTraitCollection);
     _node = node;
   }

AsyncDisplayKitTests/ASCollectionViewTests.mm

@@ -504,6 +504,45 @@
   }
 }
 
+- (void)testCellNodeIndexPathConsistency
+{
+  updateValidationTestPrologue
+
+  // Test with a visible cell
+  NSIndexPath *indexPath = [NSIndexPath indexPathForItem:2 inSection:0];
+  ASCellNode *cell = [cn nodeForItemAtIndexPath:indexPath];
+
+  // Check if cell's indexPath corresponds to the indexPath being tested
+  XCTAssertTrue(cell.indexPath.section == indexPath.section && cell.indexPath.item == indexPath.item, @"Expected the cell's indexPath to be the same as the indexPath being tested.");
+
+  // Remove an item prior to the cell's indexPath from the same section and check for indexPath consistency
+  --del->_itemCounts[indexPath.section];
+  [cn deleteItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:0 inSection:indexPath.section]]];
+  XCTAssertTrue(cell.indexPath.section == indexPath.section && cell.indexPath.item == (indexPath.item - 1), @"Expected the cell's indexPath to be updated once a cell with a lower index is deleted.");
+
+  // Remove the section that includes the indexPath and check if the cell's indexPath is now nil
+  del->_itemCounts.erase(del->_itemCounts.begin());
+  [cn deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section]];
+  XCTAssertNil(cell.indexPath, @"Expected the cell's indexPath to be nil once the section that contains the node is deleted.");
+
+  // Run the same tests but with a non-displayed cell
+  indexPath = [NSIndexPath indexPathForItem:2 inSection:(del->_itemCounts.size() - 1)];
+  cell = [cn nodeForItemAtIndexPath:indexPath];
+
+  // Check if cell's indexPath corresponds to the indexPath being tested
+  XCTAssertTrue(cell.indexPath.section == indexPath.section && cell.indexPath.item == indexPath.item, @"Expected the cell's indexPath to be the same as the indexPath in question.");
+
+  // Remove an item prior to the cell's indexPath from the same section and check for indexPath consistency
+  --del->_itemCounts[indexPath.section];
+  [cn deleteItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:0 inSection:indexPath.section]]];
+  XCTAssertTrue(cell.indexPath.section == indexPath.section && cell.indexPath.item == (indexPath.item - 1), @"Expected the cell's indexPath to be updated once a cell with a lower index is deleted.");
+
+  // Remove the section that includes the indexPath and check if the cell's indexPath is now nil
+  del->_itemCounts.pop_back();
+  [cn deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section]];
+  XCTAssertNil(cell.indexPath, @"Expected the cell's indexPath to be nil once the section that contains the node is deleted.");
+}
+
 /**
  * https://github.com/facebook/AsyncDisplayKit/issues/2011
  *

examples/VerticalWithinHorizontalScrolling/Sample/RandomCoreGraphicsNode.m

@@ -22,6 +22,8 @@
 
 @implementation RandomCoreGraphicsNode
 
+@synthesize indexPath=_indexPath;
+
 + (UIColor *)randomColor
 {
   CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0