Remove default value of offset parameter from model methods.

src/model/position.js

@@ -816,7 +816,7 @@ export default class Position {
 	 * * {@link module:engine/model/position~Position.createFromPosition}.
 	 *
 	 * @param {module:engine/model/item~Item|module:engine/model/position~Position} itemOrPosition
-	 * @param {Number|'end'|'before'|'after'} offset 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/model/item~Item model item}.
 	 */
 	static createAt( itemOrPosition, offset ) {
@@ -834,7 +834,7 @@ export default class Position {
 			} else if ( offset !== 0 && !offset ) {
 				throw new CKEditorError(
 					'model-position-createAt-required-second-parameter: ' +
-					'Position.createAt requires the second parameter offset.' );
+					'Position.createAt requires the second parameter offset when first parameter is a model item.' );
 			}
 
 			return this.createFromParentAndOffset( node, offset );

src/model/range.js

@@ -824,7 +824,7 @@ export default class Range {
 	 * or on the given {@link module:engine/model/item~Item item}.
 	 *
 	 * @param {module:engine/model/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/model/item~Item model item}.
 	 */
 	static createCollapsedAt( itemOrPosition, offset ) {

src/model/selection.js

@@ -485,7 +485,7 @@ export default class Selection {
 	 *
 	 * @fires change:range
 	 * @param {module:engine/model/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/model/item~Item model item}.
 	 */
 	setFocus( itemOrPosition, offset ) {

src/model/writer.js

@@ -153,7 +153,7 @@ export default class Writer {
 	 * @param {module:engine/model/item~Item|module:engine/model/documentfragment~DocumentFragment} item Item or document
 	 * fragment to insert.
 	 * @param {module:engine/model/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
 	 * second parameter is a {@link module:engine/model/item~Item model item}.
 	 */
 	insert( item, itemOrPosition, offset = 0 ) {
@@ -230,7 +230,7 @@ export default class Writer {
 	 * @param {String} data Text data.
 	 * @param {Object} [attributes] Text attributes.
 	 * @param {module:engine/model/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
 	 * third parameter is a {@link module:engine/model/item~Item model item}.
 	 */
 	insertText( text, attributes, itemOrPosition, offset ) {
@@ -262,7 +262,7 @@ export default class Writer {
 	 * @param {String} name Name of the element.
 	 * @param {Object} [attributes] Elements attributes.
 	 * @param {module:engine/model/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
 	 * third parameter is a {@link module:engine/model/item~Item model item}.
 	 */
 	insertElement( name, attributes, itemOrPosition, offset ) {
@@ -440,7 +440,7 @@ export default class Writer {
 	 *
 	 * @param {module:engine/model/range~Range} range Source range.
 	 * @param {module:engine/model/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
 	 * second parameter is a {@link module:engine/model/item~Item model item}.
 	 */
 	move( range, itemOrPosition, offset ) {

src/view/position.js

@@ -307,7 +307,7 @@ export default class Position {
 			} else if ( offset !== 0 && !offset ) {
 				throw new CKEditorError(
 					'view-position-createAt-required-second-parameter: ' +
-					'Position.createAt requires the second parameter offset.' );
+					'Position.createAt requires the second parameter offset when first parameter is a view item.' );
 			}
 
 			return new Position( node, offset );

tests/model/position.js

@@ -158,7 +158,7 @@ describe( 'Position', () => {
 	} );
 
 	describe( 'createAt()', () => {
-		it( 'should throw if uknown offset is passed', () => {
+		it( 'should throw if no offset is passed', () => {
 			expect( () => Position.createAt( ul ) ).to.throw( CKEditorError, /model-position-createAt-required-second-parameter/ );
 		} );
 

tests/view/position.js

@@ -152,12 +152,18 @@ describe( 'Position', () => {
 	} );
 
 	describe( 'createAt', () => {
+		it( 'should throw if no offset is passed', () => {
+			const element = new Element( 'p' );
+
+			expect( () => Position.createAt( element ) ).to.throw( CKEditorError, /view-position-createAt-required-second-parameter/ );
+		} );
+
 		it( 'should create positions from positions', () => {
 			const spy = sinon.spy( Position, 'createFromPosition' );
 
 			const p = new Element( 'p' );
 			const position = new Position( p, 0 );
-			const created = Position.createAt( position );
+			const created = Position.createAt( position, 0 );
 
 			expect( created.isEqual( position ) ).to.be.true;
 			expect( spy.calledOnce ).to.be.true;