From bc4132dba7279fdf8177aaa63687642d50ac11b6 Mon Sep 17 00:00:00 2001
From: Yury Bogdanov <yury-bogdanov@mail.ru>
Date: Mon, 18 Dec 2017 11:45:31 -0800
Subject: [PATCH] Negative size assertion

Summary:
Assertions for item's size added to prevent negative values return from IGListAdapter

Issue fixed: #977

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/992

Reviewed By: ryanolsonk

Differential Revision: D6272307

Pulled By: rnystrom

fbshipit-source-id: 844affd914329e0ca04597ada2952f1a077897af
---
 .../Internal/IGListAdapter+UICollectionView.m |  7 +++-
 Tests/IGListAdapterTests.m                    | 37 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Source/Internal/IGListAdapter+UICollectionView.m b/Source/Internal/IGListAdapter+UICollectionView.m
index 84d0973f..c6b97d37 100644
--- a/Source/Internal/IGListAdapter+UICollectionView.m
+++ b/Source/Internal/IGListAdapter+UICollectionView.m
@@ -176,7 +176,12 @@
 
 - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
     IGAssert(![self.collectionViewDelegate respondsToSelector:_cmd], @"IGListAdapter is consuming method also implemented by the collectionViewDelegate: %@", NSStringFromSelector(_cmd));
-    return [self sizeForItemAtIndexPath:indexPath];
+    
+    CGSize size = [self sizeForItemAtIndexPath:indexPath];
+    IGAssert(!isnan(size.height), @"IGListAdapter returned NaN height = %f for item at indexPath <%@>", size.height, indexPath);
+    IGAssert(!isnan(size.width), @"IGListAdapter returned NaN width = %f for item at indexPath <%@>", size.width, indexPath);
+    
+    return size;
 }
 
 - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
diff --git a/Tests/IGListAdapterTests.m b/Tests/IGListAdapterTests.m
index f80655d1..7ef91479 100644
--- a/Tests/IGListAdapterTests.m
+++ b/Tests/IGListAdapterTests.m
@@ -18,6 +18,7 @@
 #import "IGListAdapterInternal.h"
 #import "IGListTestAdapterDataSource.h"
 #import "IGListTestAdapterHorizontalDataSource.h"
+#import "IGListTestOffsettingLayout.h"
 #import "IGListTestSection.h"
 #import "IGTestSupplementarySource.h"
 #import "IGTestNibSupplementaryView.h"
@@ -1327,6 +1328,42 @@
     XCTAssertEqual(size.height, 0.0);
 }
 
+- (void)test_whenSectionControllerReturnsNANHeight_thatAssertionFires {
+    self.adapter.collectionView.collectionViewLayout = [IGListTestOffsettingLayout new];
+    self.dataSource.objects = @[@1];
+    [self.adapter reloadDataWithCompletion:nil];
+    
+    IGListTestSection *section = [self.adapter sectionControllerForObject:self.dataSource.objects[0]];
+    section.size = CGSizeMake(NAN, 1);
+    
+    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
+    XCTAssertThrows([self.adapter collectionView:self.collectionView layout:self.collectionView.collectionViewLayout sizeForItemAtIndexPath:indexPath]);
+}
+
+- (void)test_whenSectionControllerReturnsNANWidth_thatAssertionFires {
+    self.adapter.collectionView.collectionViewLayout = [IGListTestOffsettingLayout new];
+    self.dataSource.objects = @[@1];
+    [self.adapter reloadDataWithCompletion:nil];
+    
+    IGListTestSection *section = [self.adapter sectionControllerForObject:self.dataSource.objects[0]];
+    section.size = CGSizeMake(1, NAN);
+    
+    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
+    XCTAssertThrows([self.adapter collectionView:self.collectionView layout:self.collectionView.collectionViewLayout sizeForItemAtIndexPath:indexPath]);
+}
+
+- (void)test_whenSectionControllerReturnsNANWidthNANHeight_thatAssertionFires {
+    self.adapter.collectionView.collectionViewLayout = [IGListTestOffsettingLayout new];
+    self.dataSource.objects = @[@1];
+    [self.adapter reloadDataWithCompletion:nil];
+    
+    IGListTestSection *section = [self.adapter sectionControllerForObject:self.dataSource.objects[0]];
+    section.size = CGSizeMake(NAN, NAN);
+    
+    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
+    XCTAssertThrows([self.adapter collectionView:self.collectionView layout:self.collectionView.collectionViewLayout sizeForItemAtIndexPath:indexPath]);
+}
+
 - (void)test_whenSupplementarySourceReturnsNegativeSize_thatAdapterReturnsZero {
     self.dataSource.objects = @[@1];
     [self.adapter reloadDataWithCompletion:nil];