Select all columns in previous table rows when the last row is fully …

…selected.

packages/ckeditor5-table/src/tableselection.ts

@@ -368,9 +368,10 @@ export default class TableSelection extends Plugin {
 
 		const startColumn = Math.min( startLocation.column, endLocation.column );
 		const endColumn = Math.max( startLocation.column, endLocation.column );
+		const table = anchorCell.findAncestor( 'table' )!;
 
-		// 2-dimensional array of the selected cells to ease flipping the order of cells for backward selections.
-		const selectionMap: Array<Array<Element>> = new Array( endRow - startRow + 1 ).fill( null ).map( () => [] );
+		// First collect cells based on initial selection
+		let selectionMap: Array<Array<Element>> = createSelectionMap( endRow - startRow + 1 );
 
 		const walkerOptions = {
 			startRow,
@@ -379,10 +380,41 @@ export default class TableSelection extends Plugin {
 			endColumn
 		};
 
-		for ( const { row, cell } of new TableWalker( anchorCell.findAncestor( 'table' )!, walkerOptions ) ) {
+		for ( const { row, cell } of new TableWalker( table, walkerOptions ) ) {
 			selectionMap[ row - startRow ].push( cell );
 		}
 
+		// If the entire last row is selected, extend the selection to include all columns in the rows above for better UX.
+		// This prevents a scenario where selecting the entire last row (which may contain colspans) results in only one column
+		// being selected in the row above, instead of all columns (when colspan is equal to the total amount of columns in the table).
+		// This adjustment is only active for top-left to bottom-right selections.
+		// See: https://github.com/ckeditor/ckeditor5/issues/17538
+		if ( !startColumn && startLocation.row <= endLocation.row ) {
+			// Pick total width of the last selection row. It includes colspan values and not-fully selected cells.
+			const totalRowWidth = getTotalColumnsInRow( table, endRow );
+
+			// Pick width of all selected cells in the last selection row.
+			const selectedCellsWidth = getTotalCellsWidth( selectionMap[ selectionMap.length - 1 ] );
+
+			// If last row is fully selected, adjust selection to include all columns in all rows above
+			if ( selectedCellsWidth === totalRowWidth ) {
+				const totalTableColumns = tableUtils.getColumns( table );
+				const fullSelectorWalker = new TableWalker( table, {
+					startRow,
+					endRow,
+					startColumn: 0,
+					endColumn: totalTableColumns
+				} );
+
+				// Let's reset the selection map and fill it with the full row selection
+				selectionMap = createSelectionMap( endRow - startRow + 1 );
+
+				for ( const { row, cell } of fullSelectorWalker ) {
+					selectionMap[ row - startRow ].push( cell );
+				}
+			}
+		}
+
 		const flipVertically = endLocation.row < startLocation.row;
 		const flipHorizontally = endLocation.column < startLocation.column;
 
@@ -400,3 +432,42 @@ export default class TableSelection extends Plugin {
 		};
 	}
 }
+
+/**
+ * Creates a 2D array of selections based on the given size.
+ *
+ * @param size The size of the map
+ * @returns An array of arrays of elements
+ */
+function createSelectionMap( size: number ): Array<Array<Element>> {
+	return new Array( size ).fill( null ).map( () => [] );
+}
+
+/**
+ * Calculates the total width of columns in a table row by getting the sum of colspan values
+ * of all cells in that row.
+ *
+ * @param table The table element to calculate the row width for
+ * @param rowIndex The index of the row to process
+ * @returns The total width of the row (sum of colspan values)
+ */
+function getTotalColumnsInRow( table: Element, rowIndex: number ): number {
+	const cells = Array
+		.from( new TableWalker( table, { row: rowIndex } ) )
+		.map( ( { cell } ) => cell );
+
+	return getTotalCellsWidth( cells );
+}
+
+/**
+ * Calculates the total width of the given cells by summing up their colspan values.
+ *
+ * @param cells An array of table cell elements to process
+ * @returns The total width (sum of colspan values) of all provided cells
+ */
+function getTotalCellsWidth( cells: Array<Element> ): number {
+	return cells.reduce(
+		( width, cell ) => width + ( parseInt( cell.getAttribute( 'colspan' ) as string ) || 1 ),
+		0
+	);
+}

packages/ckeditor5-table/tests/commands/mergecellscommand.js

@@ -745,10 +745,9 @@ describe( 'MergeCellsCommand', () => {
 
 				expect( getData( model ) ).to.equalMarkup( modelTable( [
 					[
-						'<paragraph>[00</paragraph><paragraph>01</paragraph>' +
+						'<paragraph>[00</paragraph><paragraph>01</paragraph><paragraph>02</paragraph>' +
 						'<paragraph>10</paragraph><paragraph>11</paragraph>' +
-						'<paragraph>20</paragraph><paragraph>21]</paragraph>',
-						'02'
+						'<paragraph>20</paragraph><paragraph>21]</paragraph>'
 					]
 				] ) );
 			} );