[ios] Added deleteAllItemsFromSection to list_model

Added a function to remove all items from a section, so that only
that section can be regenerated dynamically.

Bug: 826094
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Ia873e56b0bbb8d9527b719d665ed536dddf83d41
Reviewed-on: https://chromium-review.googlesource.com/1186401
Commit-Queue: David Jean <djean@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585750}

ios/chrome/browser/ui/list_model/list_model.h

@@ -96,6 +96,10 @@ const NSInteger kItemTypeEnumZero = 100;
 // left in the section, they are removed.
 - (void)removeSectionWithIdentifier:(NSInteger)sectionIdentifier;
 
+// Deletes all items from |sectionIdentifier|, |sectionIdentifier| won't be
+// removed from the model.
+- (void)deleteAllItemsFromSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
 // Sets the header item for the section with the given |sectionIdentifier|.
 - (void)setHeader:(SupplementalType)header
     forSectionWithIdentifier:(NSInteger)sectionIdentifier;

ios/chrome/browser/ui/list_model/list_model.mm

@@ -114,6 +114,12 @@ typedef NSMutableArray<ListItem*> SectionItems;
   [_collapsedKeys removeObjectForKey:@(sectionIdentifier)];
 }
 
+- (void)deleteAllItemsFromSectionWithIdentifier:(NSInteger)sectionIdentifier {
+  NSInteger section = [self sectionForSectionIdentifier:sectionIdentifier];
+  SectionItems* items = [_sections objectAtIndex:section];
+  [items removeAllObjects];
+}
+
 - (void)setHeader:(ListItem*)header
     forSectionWithIdentifier:(NSInteger)sectionIdentifier {
   NSNumber* key = [NSNumber numberWithInteger:sectionIdentifier];

ios/chrome/browser/ui/list_model/list_model_unittest.mm

@@ -384,6 +384,70 @@ TEST_F(ListModelTest, RemoveItems) {
   EXPECT_EQ(2, indexPath.item);
 }
 
+TEST_F(ListModelTest, RemoveAllItems) {
+  ListModel* model = [[ListModel alloc] init];
+
+  [model addSectionWithIdentifier:SectionIdentifierCheese];
+  [model addItemWithType:ItemTypeCheesePepperJack
+      toSectionWithIdentifier:SectionIdentifierCheese];
+  [model addItemWithType:ItemTypeCheeseGouda
+      toSectionWithIdentifier:SectionIdentifierCheese];
+
+  [model addSectionWithIdentifier:SectionIdentifierWeasley];
+  [model addItemWithType:ItemTypeWeasleyGinny
+      toSectionWithIdentifier:SectionIdentifierWeasley];
+  [model addItemWithType:ItemTypeWeasleyArthur
+      toSectionWithIdentifier:SectionIdentifierWeasley];
+
+  [model deleteAllItemsFromSectionWithIdentifier:SectionIdentifierCheese];
+
+  // Check we still have two sections.
+  EXPECT_EQ(2, [model numberOfSections]);
+
+  // Check we have no more items in first section.
+  EXPECT_EQ(0, [model numberOfItemsInSection:0]);
+  EXPECT_EQ(2, [model numberOfItemsInSection:1]);
+
+  // Check the index path retrieval method for a single item.
+  NSIndexPath* indexPath =
+      [model indexPathForItemType:ItemTypeWeasleyGinny
+                sectionIdentifier:SectionIdentifierWeasley];
+  EXPECT_EQ(1, indexPath.section);
+  EXPECT_EQ(0, indexPath.item);
+
+  [model addItemWithType:ItemTypeCheeseGouda
+      toSectionWithIdentifier:SectionIdentifierCheese];
+
+  // Check we could still add to the section.
+  EXPECT_EQ(1, [model numberOfItemsInSection:0]);
+  EXPECT_EQ(2, [model numberOfItemsInSection:1]);
+}
+
+TEST_F(ListModelTest, RemoveAllItemsFromAnEmptySection) {
+  ListModel* model = [[ListModel alloc] init];
+
+  [model addSectionWithIdentifier:SectionIdentifierCheese];
+
+  [model addSectionWithIdentifier:SectionIdentifierWeasley];
+  [model addItemWithType:ItemTypeWeasleyGinny
+      toSectionWithIdentifier:SectionIdentifierWeasley];
+  [model addItemWithType:ItemTypeWeasleyArthur
+      toSectionWithIdentifier:SectionIdentifierWeasley];
+
+  // Check we have no more items in first section.
+  EXPECT_EQ(0, [model numberOfItemsInSection:0]);
+  EXPECT_EQ(2, [model numberOfItemsInSection:1]);
+
+  [model deleteAllItemsFromSectionWithIdentifier:SectionIdentifierCheese];
+
+  // Check we still have two sections.
+  EXPECT_EQ(2, [model numberOfSections]);
+
+  // Check we still have no items in first section.
+  EXPECT_EQ(0, [model numberOfItemsInSection:0]);
+  EXPECT_EQ(2, [model numberOfItemsInSection:1]);
+}
+
 TEST_F(ListModelTest, RemoveSections) {
   ListModel* model = [[ListModel alloc] init];