Remove default value of offset parameter from view methods.

src/view/documentselection.js

@@ -357,7 +357,7 @@ export default class DocumentSelection {
 	 * @protected
 	 * @fires change
 	 * @param {module:engine/view/item~Item|module:engine/view/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} [offset=0] Offset or one of the flags. Used only when
+	 * @param {Number|'end'|'before'|'after'} [offset] Offset or one of the flags. Used only when
 	 * first parameter is a {@link module:engine/view/item~Item view item}.
 	 */
 	_setFocus( itemOrPosition, offset ) {

src/view/downcastwriter.js

@@ -123,7 +123,7 @@ export default class DowncastWriter {
 	 * The location can be specified in the same form as {@link module:engine/view/position~Position.createAt} parameters.
 	 *
 	 * @param {module:engine/view/item~Item|module:engine/view/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} [offset=0] Offset or one of the flags. Used only when
+	 * @param {Number|'end'|'before'|'after'} [offset] Offset or one of the flags. Used only when
 	 * first parameter is a {@link module:engine/view/item~Item view item}.
 	 */
 	setSelectionFocus( itemOrPosition, offset ) {

src/view/position.js

@@ -289,7 +289,7 @@ export default class Position {
 	 * * {@link module:engine/view/position~Position.createFromPosition}.
 	 *
 	 * @param {module:engine/view/item~Item|module:engine/model/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} [offset=0] Offset or one of the flags. Used only when
+	 * @param {Number|'end'|'before'|'after'} [offset] Offset or one of the flags. Used only when
 	 * first parameter is a {@link module:engine/view/item~Item view item}.
 	 */
 	static createAt( itemOrPosition, offset ) {
@@ -304,8 +304,10 @@ export default class Position {
 				return this.createBefore( node );
 			} else if ( offset == 'after' ) {
 				return this.createAfter( node );
-			} else if ( !offset ) {
-				offset = 0;
+			} else if ( offset !== 0 && !offset ) {
+				throw new CKEditorError(
+					'view-position-createAt-required-second-parameter: ' +
+					'Position.createAt requires the second parameter offset.' );
 			}
 
 			return new Position( node, offset );

src/view/range.js

@@ -454,7 +454,7 @@ export default class Range {
 	 * or on the given {@link module:engine/view/item~Item item}.
 	 *
 	 * @param {module:engine/view/item~Item|module:engine/view/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} [offset=0] Offset or one of the flags. Used only when
+	 * @param {Number|'end'|'before'|'after'} [offset] Offset or one of the flags. Used only when
 	 * first parameter is a {@link module:engine/view/item~Item view item}.
 	 */
 	static createCollapsedAt( itemOrPosition, offset ) {

src/view/selection.js

@@ -548,7 +548,7 @@ export default class Selection {
 	 *
 	 * @fires change
 	 * @param {module:engine/view/item~Item|module:engine/view/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} [offset=0] Offset or one of the flags. Used only when
+	 * @param {Number|'end'|'before'|'after'} [offset] Offset or one of the flags. Used only when
 	 * first parameter is a {@link module:engine/view/item~Item view item}.
 	 */
 	setFocus( itemOrPosition, offset ) {

tests/view/downcastwriter/writer.js

@@ -22,7 +22,7 @@ describe( 'DowncastWriter', () => {
 
 	describe( 'setSelection()', () => {
 		it( 'should set document view selection', () => {
-			const position = ViewPosition.createAt( root );
+			const position = ViewPosition.createAt( root, 0 );
 			writer.setSelection( position );
 
 			const ranges = Array.from( doc.selection.getRanges() );
@@ -33,7 +33,7 @@ describe( 'DowncastWriter', () => {
 		} );
 
 		it( 'should be able to set fake selection', () => {
-			const position = ViewPosition.createAt( root );
+			const position = ViewPosition.createAt( root, 0 );
 			writer.setSelection( position, { fake: true, label: 'foo' } );
 
 			expect( doc.selection.isFake ).to.be.true;
@@ -43,7 +43,7 @@ describe( 'DowncastWriter', () => {
 
 	describe( 'setSelectionFocus()', () => {
 		it( 'should use selection._setFocus method internally', () => {
-			const position = ViewPosition.createAt( root );
+			const position = ViewPosition.createAt( root, 0 );
 			writer.setSelection( position );
 
 			const spy = sinon.spy( writer.document.selection, '_setFocus' );

tests/view/position.js

@@ -572,7 +572,7 @@ describe( 'Position', () => {
 		} );
 
 		it( 'for two positions in the same element returns the element', () => {
-			const startMaecenasPosition = Position.createAt( liOl2 );
+			const startMaecenasPosition = Position.createAt( liOl2, 0 );
 			const beforeTellusPosition = new Position( liOl2, 18 );
 
 			test( startMaecenasPosition, beforeTellusPosition, liOl2 );

tests/view/range.js

@@ -690,7 +690,7 @@ describe( 'Range', () => {
 		describe( 'createCollapsedAt()', () => {
 			it( 'should return new collapsed range at the given item position', () => {
 				const item = new Element( 'p', null, new Text( 'foo' ) );
-				const range = Range.createCollapsedAt( item );
+				const range = Range.createCollapsedAt( item, 0 );
 
 				expect( range.start.parent ).to.equal( item );
 				expect( range.start.offset ).to.equal( 0 );

tests/view/view/view.js

@@ -478,8 +478,8 @@ describe( 'view', () => {
 
 					return element;
 				} );
-				writer.insert( ViewPosition.createAt( p ), ui );
-				writer.insert( ViewPosition.createAt( viewRoot ), p );
+				writer.insert( ViewPosition.createAt( p, 0 ), ui );
+				writer.insert( ViewPosition.createAt( viewRoot, 0 ), p );
 			} );
 
 			expect( renderingCalled ).to.be.true;