Account for table view cell separator when reporting height (#2883)

Author: Adlai Holler

AsyncDisplayKit/ASTableView.mm

@@ -819,7 +819,18 @@ - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(N
 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
 {
   ASCellNode *node = [_dataController nodeAtIndexPath:indexPath];
-  return node.calculatedSize.height;
+  CGFloat height = node.calculatedSize.height;
+  
+  /**
+   * Weirdly enough, Apple expects the return value here to _include_ the height
+   * of the separator, if there is one! So if our node wants to be 43.5, we need
+   * to return 44. UITableView will make a cell of height 44 with a content view
+   * of height 43.5.
+   */
+  if (tableView.separatorStyle != UITableViewCellSeparatorStyleNone) {
+    height += 1.0 / ASScreenScale();
+  }
+  return height;
 }
 
 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView

AsyncDisplayKitTests/ASTableViewTests.mm

@@ -19,6 +19,7 @@
 #import "ASTableView+Undeprecated.h"
 #import <JGMethodSwizzler/JGMethodSwizzler.h>
 #import "ASXCTExtensions.h"
+#import "ASInternalHelpers.h"
 
 #define NumberOfSections 10
 #define NumberOfReloadIterations 50
@@ -234,7 +235,7 @@ - (void)testDataSourceImplementsNecessaryMethods
 - (void)testConstrainedSizeForRowAtIndexPath
 {
   // Initial width of the table view is non-zero and all nodes are measured with this size.
-  // Any subsequence size change must trigger a relayout.
+  // Any subsequent size change must trigger a relayout.
   // Width and height are swapped so that a later size change will simulate a rotation
   ASTestTableView *tableView = [[ASTestTableView alloc] __initWithFrame:CGRectMake(0, 0, 100, 400)
                                                                   style:UITableViewStylePlain];
@@ -249,12 +250,13 @@ - (void)testConstrainedSizeForRowAtIndexPath
   [tableView setNeedsLayout];
   [tableView layoutIfNeeded];
 
+  CGFloat separatorHeight = 1.0 / ASScreenScale();
   for (int section = 0; section < NumberOfSections; section++) {
       for (int row = 0; row < [tableView numberOfRowsInSection:section]; row++) {
         NSIndexPath *indexPath = [NSIndexPath indexPathForRow:row inSection:section];
         CGRect rect = [tableView rectForRowAtIndexPath:indexPath];
         XCTAssertEqual(rect.size.width, 100);  // specified width should be ignored for table
-        XCTAssertEqual(rect.size.height, 42);
+        XCTAssertEqual(rect.size.height, 42 + separatorHeight);
       }
   }
 }
@@ -775,7 +777,7 @@ - (void)testIssue2252
   [window layoutIfNeeded];
   [node waitUntilAllUpdatesAreCommitted];
   XCTAssertEqual(node.view.numberOfSections, NumberOfSections);
-  ASXCTAssertEqualRects(CGRectMake(0, 32, 375, 43.5), [node rectForRowAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]], @"This text requires very specific geometry. The rect for the first row should match up.");
+  ASXCTAssertEqualRects(CGRectMake(0, 32, 375, 44), [node rectForRowAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]], @"This text requires very specific geometry. The rect for the first row should match up.");
 
   __unused XCTestExpectation *e = [self expectationWithDescription:@"Did a bunch of rounds of updates."];
   NSInteger totalCount = 20;