Do not reload UI if the Reading List entry does not exist

The custom accessibility actions check for the existence of the ReadingListModel
entry when configuring a cell. This CL changes this behavior to do nothing when
the entry does not exist instead of reloading the UI.

BUG=676290, 701956

Review-Url: https://codereview.chromium.org/2750623006
Cr-Commit-Position: refs/heads/master@{#457382}

ios/chrome/browser/ui/reading_list/reading_list_collection_view_controller.mm

@@ -120,7 +120,7 @@ using ItemsMapByDate = std::multimap<int64_t, ReadingListCollectionViewItem*>;
 // Stops observing the ReadingListModel.
 - (void)stopObservingReadingListModel;
 // Returns the ReadingListEntry associated with the |item|. If there is not such
-// an entry, returns nullptr and reloads the UI.
+// an entry, returns nullptr.
 - (const ReadingListEntry*)readingListEntryForItem:
     (ReadingListCollectionViewItem*)item;
 // Updates the toolbar state according to the selected items.
@@ -698,12 +698,6 @@ using ItemsMapByDate = std::multimap<int64_t, ReadingListCollectionViewItem*>;
   const ReadingListEntry* readingListEntry =
       self.readingListModel->GetEntryByURL(item.url);
 
-  if (!readingListEntry) {
-    // The entry has been removed from the model, reload all data to synchronize
-    // the UI with the model.
-    [self reloadData];
-  }
-
   return readingListEntry;
 }
 

ios/chrome/browser/ui/reading_list/reading_list_egtest.mm

@@ -13,6 +13,7 @@
 #import "ios/chrome/browser/ui/commands/generic_chrome_command.h"
 #include "ios/chrome/browser/ui/commands/ios_command_ids.h"
 #import "ios/chrome/browser/ui/reading_list/reading_list_collection_view_item.h"
+#import "ios/chrome/browser/ui/reading_list/reading_list_empty_collection_background.h"
 #include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "ios/chrome/grit/ios_theme_resources.h"
@@ -195,6 +196,12 @@ size_t ModelReadSize(ReadingListModel* model) {
   }
   return size;
 }
+
+// Returns a match for the Reading List Empty Collection Background.
+id<GREYMatcher> EmptyBackground() {
+  return grey_accessibilityID(
+      [ReadingListEmptyCollectionBackground accessibilityIdentifier]);
+}
 }  // namespace
 
 // Test class for the Reading List menu.
@@ -528,4 +535,29 @@ size_t ModelReadSize(ReadingListModel* model) {
                  GetReadingListModel()->unread_size());
 }
 
+// Tests that you can delete multiple read items in the Reading List without
+// creating a crash (crbug.com/701956).
+- (void)testDeleteMultipleItems {
+  // Add entries.
+  ReadingListModel* model = GetReadingListModel();
+  for (int i = 0; i < 11; i++) {
+    std::string increment = std::to_string(i);
+    model->AddEntry(GURL(kReadURL + increment),
+                    std::string(kReadTitle + increment),
+                    reading_list::ADDED_VIA_CURRENT_APP);
+    model->SetReadStatus(GURL(kReadURL + increment), true);
+  }
+
+  // Delete them from the Reading List view.
+  OpenReadingList();
+  [[EarlGrey selectElementWithMatcher:EmptyBackground()]
+      assertWithMatcher:grey_nil()];
+  TapButtonWithID(IDS_IOS_READING_LIST_EDIT_BUTTON);
+  TapButtonWithID(IDS_IOS_READING_LIST_DELETE_ALL_READ_BUTTON);
+
+  // Verify the background string is displayed.
+  [[EarlGrey selectElementWithMatcher:EmptyBackground()]
+      assertWithMatcher:grey_notNil()];
+}
+
 @end

ios/chrome/browser/ui/reading_list/reading_list_empty_collection_background.h

@@ -14,6 +14,8 @@
 - (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
 - (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;
 
++ (NSString*)accessibilityIdentifier;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_READING_LIST_READING_LIST_EMPTY_COLLECTION_BACKGROUND_H_

ios/chrome/browser/ui/reading_list/reading_list_empty_collection_background.mm

@@ -64,6 +64,8 @@ const CGFloat kPercentageFromTopForPosition = 0.4;
 
 @implementation ReadingListEmptyCollectionBackground
 
+#pragma mark - Public
+
 - (instancetype)init {
   self = [super initWithFrame:CGRectZero];
   if (self) {
@@ -172,6 +174,8 @@ const CGFloat kPercentageFromTopForPosition = 0.4;
     label.numberOfLines = 0;
     label.textAlignment = NSTextAlignmentCenter;
     label.accessibilityLabel = accessibilityLabel;
+    label.accessibilityIdentifier =
+        [ReadingListEmptyCollectionBackground accessibilityIdentifier];
     [label setTranslatesAutoresizingMaskIntoConstraints:NO];
     [self addSubview:label];
 
@@ -185,6 +189,12 @@ const CGFloat kPercentageFromTopForPosition = 0.4;
   return self;
 }
 
++ (NSString*)accessibilityIdentifier {
+  return @"ReadingListBackgroundViewIdentifier";
+}
+
+#pragma mark - Private
+
 - (void)attachIconNamed:(NSString*)iconName
                toString:(NSMutableAttributedString*)instructionString
               withCaret:(NSMutableAttributedString*)caret