Fix BL-12890 Duplicate thumbnails

src/BloomExe/Collection/BookCollection.cs

@@ -306,12 +306,19 @@ public void UpdateBookInfo(BookInfo info)
 			_bookInfos.Insert(newIndex, info);
 			NotifyCollectionChanged();
 		}
-
-		public void AddBookInfo(BookInfo bookInfo)
-		{
-			_bookInfos.Add(bookInfo);
-			NotifyCollectionChanged();
-		}
+        private void AddBookInfoInternalNoSideEffects(BookInfo bookInfo)
+        {
+            // Note BL-12890 it's actually the norm, when we add a book, that the new book will already be there
+            // by the time we officially add it.
+            if (_bookInfos.FindIndex(i => i.Id == bookInfo.Id) < 0)
+                _bookInfos.Add(bookInfo);
+        }
+
+        public void AddBookInfo(BookInfo bookInfo)
+        {
+            AddBookInfoInternalNoSideEffects(bookInfo);
+            NotifyCollectionChanged();
+        }
 
 		/// <summary>
 		/// Insert a book into the appropriate place. If there is already a book with the same FolderPath, replace it.
@@ -331,13 +338,13 @@ public void InsertBookInfo(BookInfo bookInfo)
 				if (compare > 0)
 				{
 					_bookInfos.Insert(i, bookInfo);
-					return;
-				}
-			}
-			_bookInfos.Add(bookInfo);
-		}
+                    return;
+                }
+            }
+            AddBookInfoInternalNoSideEffects(bookInfo);
+        }
 
-		private bool BackupFileExists(string folderPath)
+        private bool BackupFileExists(string folderPath)
 		{
 			var bakFiles = Directory.GetFiles(folderPath, BookStorage.BackupFilename);
 			return bakFiles.Length == 1 && RobustFile.Exists(bakFiles[0]);

src/BloomExe/CollectionTab/CollectionModel.cs

@@ -776,12 +776,15 @@ private void CreateFromSourceBook(Book.Book sourceBook)
 				// (We can't fix this by reordering things, because there will also be problems if we attempt
 				// to select an item before it is present in the collection to select.)
 				// We know this is a new book object, so there's no point in using EnsureUpToDate.
-				// When we later select it, that code uses EnsureUpToDate and will not do it again.
-				newBook.BringBookUpToDate(new NullProgress(), false);
+                // When we later select it, that code uses EnsureUpToDate and will not do it again.
+                newBook.BringBookUpToDate(new NullProgress(), false);
 
-				TheOneEditableCollection.AddBookInfo(newBook.BookInfo);
+                // You'd think this was needed, but it's not. The book is already in the collection due to
+                // the BringBookUpToDate side effects. However, I'm too chicken to rely on that, so instead
+                // I made AddBookInfo() avoid adding a duplicate (BL-12890)
+                TheOneEditableCollection.AddBookInfo(newBook.BookInfo);
 
-				if (_bookSelection != null)
+                if (_bookSelection != null)
 				{
 					Book.Book.SourceToReportForNextRename = Path.GetFileName(sourceBook.FolderPath);
 					_bookSelection.SelectBook(newBook, aboutToEdit: true);