/** * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved. * For licensing, see LICENSE.md. */ /** * @module engine/model/schema */ import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror'; import ObservableMixin from '@ckeditor/ckeditor5-utils/src/observablemixin'; import mix from '@ckeditor/ckeditor5-utils/src/mix'; import Range from './range'; import Position from './position'; import Element from './element'; import TreeWalker from './treewalker'; /** * The model's schema. It defines allowed and disallowed structures of nodes as well as nodes' attributes. * The schema is usually defined by features and based on them the editing framework and features * make decisions how to change and process the model. * * The instance of schema is available in {@link module:engine/model/model~Model#schema `editor.model.schema`}. * * # Schema definitions * * Schema defines allowed model structures and allowed attributes separately. They are also checked separately * by using the {@link ~Schema#checkChild} and {@link ~Schema#checkAttribute} methods. * * ## Defining allowed structures * * When a feature introduces a model element it should register it in the schema. Besides * defining that such an element may exist in the model, the feature also needs to define where * this element may be placed: * * schema.register( 'myElement', { * allowIn: '$root' * } ); * * This lets the schema know that `` may be a child of the `<$root>` element. `$root` is one of generic * nodes defined by the editing framework. By default, the editor names the main root element a `<$root>`, * so the above definition allows `` in the main editor element. * * In other words, this would be correct: * * <$root> * * While this would not be correct: * * <$root> * * ## Generic items * * There are three basic generic items: `$root`, `$block` and `$text`. * They are defined as follows: * * this.schema.register( '$root', { * isLimit: true * } ); * this.schema.register( '$block', { * allowIn: '$root', * isBlock: true * } ); * this.schema.register( '$text', { * allowIn: '$block' * } ); * * These definitions can then be reused by features to create their own definitions in a more extensible way. * For example, the {@link module:paragraph/paragraph~Paragraph} feature will define its item as: * * schema.register( 'paragraph', { * inheritAllFrom: '$block' * } ); * * Which translates to: * * schema.register( 'paragraph', { * allowWhere: '$block', * allowContentOf: '$block', * allowAttributesOf: '$block', * inheritTypesFrom: '$block' * } ); * * Which can be read as: * * * The `` element will be allowed in elements in which `<$block>` is allowed (e.g. in `<$root>`). * * The `` element will allow all nodes which are allowed in `<$block>` (e.g. `$text`). * * The `` element will allow all attributes allowed on `<$block>`. * * The `` element will inherit all `is*` properties of `<$block>` (e.g. `isBlock`). * * Thanks to the fact that ``'s definition is inherited from `<$block>` other features can use the `<$block>` * type to indirectly extend ``'s definition. For example, the {@link module:block-quote/blockquote~BlockQuote} * feature does this: * * schema.register( 'blockQuote', { * allowWhere: '$block', * allowContentOf: '$root' * } ); * * Thanks to that, despite the fact that block quote and paragraph features know nothing about themselves, paragraphs * will be allowed in block quotes and block quotes will be allowed in all places where blocks are. So if anyone will * register a `
` element (with `allowContentOf: '$root'` rule), that `
` elements will allow * block quotes too. * * The side effect of such a definition inheritance is that now `
` is allowed in `
` which needs to be * resolved by a callback which will disallow this specific structure. * * You can read more about the format of an item definition in {@link module:engine/model/schema~SchemaItemDefinition}. * * ## Defining advanced rules in `checkChild()`'s callbacks * * The {@link ~Schema#checkChild} method which is the base method used to check whether some element is allowed in a given structure * is {@link module:utils/observablemixin~ObservableMixin#decorate a decorated method}. * It means that you can add listeners to implement your specific rules which are not limited by the declarative * {@link module:engine/model/schema~SchemaItemDefinition API}. * * Those listeners can be added either by listening directly to the {@link ~Schema#event:checkChild} event or * by using the handy {@link ~Schema#addChildCheck} method. * * For instance, the block quote feature defines such a listener to disallow nested `
` structures: * * schema.addChildCheck( context, childDefinition ) => { * // Note that context is automatically normalized to SchemaContext instance and * // child to its definition (SchemaCompiledItemDefinition). * * // If checkChild() is called with a context that ends with blockQuote and blockQuote as a child * // to check, make the checkChild() method return false. * if ( context.endsWith( 'blockQuote' ) && childDefinition.name == 'blockQuote' ) { * return false; * } * } ); * * ## Defining attributes * * TODO * * ## Implementing additional constraints * * Schema's capabilities were limited to simple (and atomic) {@link ~Schema#checkChild} and * {@link ~Schema#checkAttribute} checks on purpose. * One may imagine that schema should support defining more complex rules such as * "element `` must be always followed by ``". * While it is feasible to create an API which would enable feeding the schema with such definitions, * it is unfortunately unrealistic to then expect that every editing feature will consider those rules when processing the model. * It is also unrealistic to expect that it will be done automatically by the schema and the editing engine themselves. * * For instance, let's get back to the "element `` must be always followed by ``" rule and this initial content: * * <$root> * foo * bar[bom * bom]bar * * * Now, imagine that the user presses the "block quote" button. Usually it would wrap the two selected blocks * (`` and ``) with a `
` element: * * <$root> * foo *
* bar[bom * bom]bar *
* * * But it turns out that this creates an incorrect structure – `` is not followed by `` anymore. * * What should happen instead? There are at least 4 possible solutions: the block quote feature should not be * applicable in such a context, someone should create a new `` right after ``, `` should be moved * inside `
` together with `` or vice versa. * * While this is a relatively simple scenario (unlike most real-time collaboration scenarios), * it turns out that it's already hard to say what should happen and who should react to fix this content. * * Therefore, if your editor needs to implement such rules, you should do that through model's post-fixers * fixing incorrect content or actively prevent such situations (e.g. by disabling certain features). * It means that those constraints will be defined specifically for your scenario by your code which * makes their implementation much easier. * * So the answer for who and how should implement additional constraints is your features or your editor * through CKEditor 5's rich and open API. * * @mixes module:utils/observablemixin~ObservableMixin */ export default class Schema { /** * Creates schema instance. */ constructor() { this._sourceDefinitions = {}; this.decorate( 'checkChild' ); this.decorate( 'checkAttribute' ); this.on( 'checkAttribute', ( evt, args ) => { args[ 0 ] = new SchemaContext( args[ 0 ] ); }, { priority: 'highest' } ); this.on( 'checkChild', ( evt, args ) => { args[ 0 ] = new SchemaContext( args[ 0 ] ); args[ 1 ] = this.getDefinition( args[ 1 ] ); }, { priority: 'highest' } ); } /** * Registers schema item. Can only be called once for every item name. * * schema.register( 'paragraph', { * inheritAllFrom: '$block' * } ); * * @param {String} itemName * @param {module:engine/model/schema~SchemaItemDefinition} definition */ register( itemName, definition ) { if ( this._sourceDefinitions[ itemName ] ) { // TODO docs throw new CKEditorError( 'schema-cannot-register-item-twice: A single item cannot be registered twice in the schema.', { itemName } ); } this._sourceDefinitions[ itemName ] = [ Object.assign( {}, definition ) ]; this._clearCache(); } /** * Extends a {@link #register registered} item's definition. * * Extending properties such as `allowIn` will add more items to the existing properties, * while redefining properties such as `isBlock` will override the previously defined ones. * * schema.register( 'foo', { * allowIn: '$root', * isBlock: true; * } ); * schema.extend( 'foo', { * allowIn: 'blockQuote', * isBlock: false * } ); * * schema.getDefinition( 'foo' ); * // { * // allowIn: [ '$root', 'blockQuote' ], * // isBlock: false * // } * * @param {String} itemName * @param {module:engine/model/schema~SchemaItemDefinition} definition */ extend( itemName, definition ) { if ( !this._sourceDefinitions[ itemName ] ) { // TODO docs throw new CKEditorError( 'schema-cannot-extend-missing-item: Cannot extend an item which was not registered yet.', { itemName } ); } this._sourceDefinitions[ itemName ].push( Object.assign( {}, definition ) ); this._clearCache(); } /** * Returns all registered items. * * @returns {Object.} */ getDefinitions() { if ( !this._compiledDefinitions ) { this._compile(); } return this._compiledDefinitions; } /** * Returns a definition of the given item or `undefined` if item is not registered. * * @param {module:engine/model/item~Item|module:engine/model/schema~SchemaContextItem|String} item * @returns {module:engine/model/schema~SchemaCompiledItemDefinition} */ getDefinition( item ) { let itemName; if ( typeof item == 'string' ) { itemName = item; } else if ( item.is && ( item.is( 'text' ) || item.is( 'textProxy' ) ) ) { itemName = '$text'; } // Element or module:engine/model/schema~SchemaContextItem. else { itemName = item.name; } return this.getDefinitions()[ itemName ]; } /** * Returns `true` if the given item is registered in the schema. * * schema.isRegistered( 'paragraph' ); // -> true * schema.isRegistered( editor.model.document.getRoot() ); // -> true * schema.isRegistered( 'foo' ); // -> false * * @param {module:engine/model/item~Item|module:engine/model/schema~SchemaContextItem|String} item */ isRegistered( item ) { return !!this.getDefinition( item ); } /** * Returns `true` if the given item is defined to be * a block by {@link module:engine/model/schema~SchemaItemDefinition}'s `isBlock` property. * * schema.isBlock( 'paragraph' ); // -> true * schema.isBlock( '$root' ); // -> false * * const paragraphElement = writer.createElement( 'paragraph' ); * schema.isBlock( paragraphElement ); // -> true * * @param {module:engine/model/item~Item|module:engine/model/schema~SchemaContextItem|String} item */ isBlock( item ) { const def = this.getDefinition( item ); return !!( def && def.isBlock ); } /** * Returns `true` if the given item is defined to be * a limit element by {@link module:engine/model/schema~SchemaItemDefinition}'s `isLimit` or `isObject` property * (all objects are also limits). * * schema.isLimit( 'paragraph' ); // -> false * schema.isLimit( '$root' ); // -> true * schema.isLimit( editor.model.document.getRoot() ); // -> true * schema.isLimit( 'image' ); // -> true * * @param {module:engine/model/item~Item|module:engine/model/schema~SchemaContextItem|String} item */ isLimit( item ) { const def = this.getDefinition( item ); if ( !def ) { return false; } return !!( def.isLimit || def.isObject ); } /** * Returns `true` if the given item is defined to be * a object element by {@link module:engine/model/schema~SchemaItemDefinition}'s `isObject` property. * * schema.isObject( 'paragraph' ); // -> false * schema.isObject( 'image' ); // -> true * * const imageElement = writer.createElement( 'image' ); * schema.isObject( imageElement ); // -> true * * @param {module:engine/model/item~Item|module:engine/model/schema~SchemaContextItem|String} item */ isObject( item ) { const def = this.getDefinition( item ); return !!( def && def.isObject ); } /** * Checks whether the given node (`child`) can be a child of the given context. * * schema.checkChild( model.document.getRoot(), paragraph ); // -> false * * schema.register( 'paragraph', { * allowIn: '$root' * } ); * schema.checkChild( model.document.getRoot(), paragraph ); // -> true * * Note: When verifying whether the given node can be a child of the given context, the * schema also verifies the entire context — from its root to its last element. Therefore, it is possible * for `checkChild()` to return `false` even though the context's last element can contain the checked child. * It happens if one of the context's elements does not allow its child. * * @fires checkChild * @param {module:engine/model/schema~SchemaContextDefinition} context The context in which the child will be checked. * @param {module:engine/model/node~Node|String} def The child to check. */ checkChild( context, def ) { // Note: context and child are already normalized here to a SchemaContext and SchemaCompiledItemDefinition. if ( !def ) { return false; } return this._checkContextMatch( def, context ); } /** * Checks whether the given attribute can be applied in the given context (on the last * item of the context). * * schema.checkAttribute( textNode, 'bold' ); // -> false * * schema.extend( '$text', { * allowAttributes: 'bold' * } ); * schema.checkAttribute( textNode, 'bold' ); // -> true * * @fires checkAttribute * @param {module:engine/model/schema~SchemaContextDefinition} context The context in which the attribute will be checked. * @param {String} attributeName */ checkAttribute( context, attributeName ) { const def = this.getDefinition( context.last ); if ( !def ) { return false; } return def.allowAttributes.includes( attributeName ); } /** * Checks whether the given element (`elementToMerge`) can be merged with the specified base element (`positionOrBaseElement`). * * In other words — whether `elementToMerge`'s children {@link #checkChild are allowed} in the `positionOrBaseElement`. * * This check ensures that elements merged with {@link module:engine/model/writer~Writer#merge `Writer#merge()`} * will be valid. * * Instead of elements, you can pass the instance of the {@link module:engine/model/position~Position} class as the * `positionOrBaseElement`. It means that the elements before and after the position will be checked whether they can be merged. * * @param {module:engine/model/position~Position|module:engine/model/element~Element} positionOrBaseElement The position or base * element to which the `elementToMerge` will be merged. * @param {module:engine/model/element~Element} elementToMerge The element to merge. Required if `positionOrBaseElement` is an element. * @returns {Boolean} */ checkMerge( positionOrBaseElement, elementToMerge = null ) { if ( positionOrBaseElement instanceof Position ) { const nodeBefore = positionOrBaseElement.nodeBefore; const nodeAfter = positionOrBaseElement.nodeAfter; if ( !( nodeBefore instanceof Element ) ) { /** * The node before the merge position must be an element. * * @error schema-check-merge-no-element-before */ throw new CKEditorError( 'schema-check-merge-no-element-before: The node before the merge position must be an element.' ); } if ( !( nodeAfter instanceof Element ) ) { /** * The node after the merge position must be an element. * * @error schema-check-merge-no-element-after */ throw new CKEditorError( 'schema-check-merge-no-element-after: The node after the merge position must be an element.' ); } return this.checkMerge( nodeBefore, nodeAfter ); } for ( const child of elementToMerge.getChildren() ) { if ( !this.checkChild( positionOrBaseElement, child ) ) { return false; } } return true; } /** * Allows registering a callback to the {@link #checkChild} method calls. * * Callbacks allow you to implement rules which are not otherwise possible to achieve * by using the declarative API of {@link module:engine/model/schema~SchemaItemDefinition}. * For example, by using this method you can disallow elements in specific contexts. * * This method is a shorthand for using the {@link #event:checkChild} event. For even better control, * you can use that event instead. * * Example: * * // Disallow heading1 directly inside a blockQuote. * schema.addChildCheck( ( context, childDefinition ) => { * if ( context.endsWith( 'blockQuote' ) && childDefinition.name == 'heading1' ) { * return false; * } * } ); * * Which translates to: * * schema.on( 'checkChild', ( evt, args ) => { * const context = args[ 0 ]; * const childDefinition = args[ 1 ]; * * if ( context.endsWith( 'blockQuote' ) && childDefinition && childDefinition.name == 'heading1' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkChild()'s return value. * evt.return = false; * } * }, { priority: 'high' } ); * * @param {Function} callback The callback to be called. It is called with two parameters: * {@link module:engine/model/schema~SchemaContext} (context) instance and * {@link module:engine/model/schema~SchemaCompiledItemDefinition} (child-to-check definition). * The callback may return `true/false` to override `checkChild()`'s return value. If it does not return * a boolean value, the default algorithm (or other callbacks) will define `checkChild()`'s return value. */ addChildCheck( callback ) { this.on( 'checkChild', ( evt, [ ctx, childDef ] ) => { // checkChild() was called with a non-registered child. // In 99% cases such check should return false, so not to overcomplicate all callbacks // don't even execute them. if ( !childDef ) { return; } const retValue = callback( ctx, childDef ); if ( typeof retValue == 'boolean' ) { evt.stop(); evt.return = retValue; } }, { priority: 'high' } ); } /** * Allows registering a callback to the {@link #checkAttribute} method calls. * * Callbacks allow you to implement rules which are not otherwise possible to achieve * by using the declarative API of {@link module:engine/model/schema~SchemaItemDefinition}. * For example, by using this method you can disallow attribute if node to which it is applied * is contained within some other element (e.g. you want to disallow `bold` on `$text` within `heading1`). * * This method is a shorthand for using the {@link #event:checkAttribute} event. For even better control, * you can use that event instead. * * Example: * * // Disallow bold on $text inside heading1. * schema.addChildCheck( ( context, attributeName ) => { * if ( context.endsWith( 'heading1 $text' ) && attributeName == 'bold' ) { * return false; * } * } ); * * Which translates to: * * schema.on( 'checkAttribute', ( evt, args ) => { * const context = args[ 0 ]; * const attributeName = args[ 1 ]; * * if ( context.endsWith( 'heading1 $text' ) && attributeName == 'bold' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkAttribute()'s return value. * evt.return = false; * } * }, { priority: 'high' } ); * * @param {Function} callback The callback to be called. It is called with two parameters: * {@link module:engine/model/schema~SchemaContext} (context) instance and attribute name. * The callback may return `true/false` to override `checkAttribute()`'s return value. If it does not return * a boolean value, the default algorithm (or other callbacks) will define `checkAttribute()`'s return value. */ addAttributeCheck( callback ) { this.on( 'checkAttribute', ( evt, [ ctx, attributeName ] ) => { const retValue = callback( ctx, attributeName ); if ( typeof retValue == 'boolean' ) { evt.stop(); evt.return = retValue; } }, { priority: 'high' } ); } /** * Returns the lowest {@link module:engine/model/schema~Schema#isLimit limit element} containing the entire * selection or the root otherwise. * * @param {module:engine/model/selection~Selection|module:engine/model/documentselection~DocumentSelection} selectionOrRangeOrPosition * Selection which returns the common ancestor. * @returns {module:engine/model/element~Element} */ getLimitElement( selectionOrRangeOrPosition ) { let element; if ( selectionOrRangeOrPosition instanceof Position ) { element = selectionOrRangeOrPosition.parent; } else { const ranges = selectionOrRangeOrPosition instanceof Range ? [ selectionOrRangeOrPosition ] : Array.from( selectionOrRangeOrPosition.getRanges() ); // Find the common ancestor for all selection's ranges. element = ranges .reduce( ( element, range ) => { const rangeCommonAncestor = range.getCommonAncestor(); if ( !element ) { return rangeCommonAncestor; } return element.getCommonAncestor( rangeCommonAncestor, { includeSelf: true } ); }, null ); } while ( !this.isLimit( element ) ) { if ( element.parent ) { element = element.parent; } else { break; } } return element; } /** * Checks whether the attribute is allowed in selection: * * * if the selection is not collapsed, then checks if the attribute is allowed on any of nodes in that range, * * if the selection is collapsed, then checks if on the selection position there's a text with the * specified attribute allowed. * * @param {module:engine/model/selection~Selection|module:engine/model/documentselection~DocumentSelection} selection * Selection which will be checked. * @param {String} attribute The name of the attribute to check. * @returns {Boolean} */ checkAttributeInSelection( selection, attribute ) { if ( selection.isCollapsed ) { // Check whether schema allows for a text with the attribute in the selection. return this.checkAttribute( [ ...selection.getFirstPosition().getAncestors(), '$text' ], attribute ); } else { const ranges = selection.getRanges(); // For all ranges, check nodes in them until you find a node that is allowed to have the attribute. for ( const range of ranges ) { for ( const value of range ) { if ( this.checkAttribute( value.item, attribute ) ) { // If we found a node that is allowed to have the attribute, return true. return true; } } } } // If we haven't found such node, return false. return false; } /** * Transforms the given set of ranges into a set of ranges where the given attribute is allowed (and can be applied). * * @param {Array.} ranges Ranges to be validated. * @param {String} attribute The name of the attribute to check. * @returns {Array.} Ranges in which the attribute is allowed. */ getValidRanges( ranges, attribute ) { const validRanges = []; for ( const range of ranges ) { let last = range.start; let from = range.start; const to = range.end; for ( const value of range.getWalker() ) { if ( !this.checkAttribute( value.item, attribute ) ) { if ( !from.isEqual( last ) ) { validRanges.push( new Range( from, last ) ); } from = value.nextPosition; } last = value.nextPosition; } if ( from && !from.isEqual( to ) ) { validRanges.push( new Range( from, to ) ); } } return validRanges; } /** * Basing on given the `position`, finds and returns a {@link module:engine/model/range~Range range} which is * nearest to that `position` and is a correct range for selection. * * The correct selection range might be collapsed when it is located in a position where the text node can be placed. * Non-collapsed range is returned when selection can be placed around element marked as an "object" in * the {@link module:engine/model/schema~Schema schema}. * * Direction of searching for the nearest correct selection range can be specified as: * * * `both` - searching will be performed in both ways, * * `forward` - searching will be performed only forward, * * `backward` - searching will be performed only backward. * * When valid selection range cannot be found, `null` is returned. * * @param {module:engine/model/position~Position} position Reference position where new selection range should be looked for. * @param {'both'|'forward'|'backward'} [direction='both'] Search direction. * @returns {module:engine/model/range~Range|null} Nearest selection range or `null` if one cannot be found. */ getNearestSelectionRange( position, direction = 'both' ) { // Return collapsed range if provided position is valid. if ( this.checkChild( position, '$text' ) ) { return new Range( position ); } let backwardWalker, forwardWalker; if ( direction == 'both' || direction == 'backward' ) { backwardWalker = new TreeWalker( { startPosition: position, direction: 'backward' } ); } if ( direction == 'both' || direction == 'forward' ) { forwardWalker = new TreeWalker( { startPosition: position } ); } for ( const data of combineWalkers( backwardWalker, forwardWalker ) ) { const type = ( data.walker == backwardWalker ? 'elementEnd' : 'elementStart' ); const value = data.value; if ( value.type == type && this.isObject( value.item ) ) { return Range.createOn( value.item ); } if ( this.checkChild( value.nextPosition, '$text' ) ) { return new Range( value.nextPosition ); } } return null; } /** * Tries to find position ancestors that allows to insert given node. * It starts searching from the given position and goes node by node to the top of the model tree * as long as {@link module:engine/model/schema~Schema#isLimit limit element}, * {@link module:engine/model/schema~Schema#isObject object element} or top-most ancestor won't be reached. * * @params {module:engine/model/node~Node} node Node for which allowed parent should be found. * @params {module:engine/model/position~Position} position Position from searching will start. * @returns {module:engine/model/element~Element|null} element Allowed parent or null if nothing was found. */ findAllowedParent( node, position ) { let parent = position.parent; while ( parent ) { if ( this.checkChild( parent, node ) ) { return parent; } // Do not split limit elements. if ( this.isLimit( parent ) ) { return null; } parent = parent.parent; } return null; } /** * Removes attributes disallowed by the schema. * * @param {Iterable.} nodes Nodes that will be filtered. * @param {module:engine/model/writer~Writer} writer */ removeDisallowedAttributes( nodes, writer ) { for ( const node of nodes ) { for ( const attribute of node.getAttributeKeys() ) { if ( !this.checkAttribute( node, attribute ) ) { writer.removeAttribute( attribute, node ); } } if ( node.is( 'element' ) ) { this.removeDisallowedAttributes( node.getChildren(), writer ); } } } /** * @private */ _clearCache() { this._compiledDefinitions = null; } /** * @private */ _compile() { const compiledDefinitions = {}; const sourceRules = this._sourceDefinitions; const itemNames = Object.keys( sourceRules ); for ( const itemName of itemNames ) { compiledDefinitions[ itemName ] = compileBaseItemRule( sourceRules[ itemName ], itemName ); } for ( const itemName of itemNames ) { compileAllowContentOf( compiledDefinitions, itemName ); } for ( const itemName of itemNames ) { compileAllowWhere( compiledDefinitions, itemName ); } for ( const itemName of itemNames ) { compileAllowAttributesOf( compiledDefinitions, itemName ); compileInheritPropertiesFrom( compiledDefinitions, itemName ); } for ( const itemName of itemNames ) { cleanUpAllowIn( compiledDefinitions, itemName ); cleanUpAllowAttributes( compiledDefinitions, itemName ); } this._compiledDefinitions = compiledDefinitions; } /** * @private * @param {module:engine/model/schema~SchemaCompiledItemDefinition} def * @param {module:engine/model/schema~SchemaContext} context * @param {Number} contextItemIndex */ _checkContextMatch( def, context, contextItemIndex = context.length - 1 ) { const contextItem = context.getItem( contextItemIndex ); if ( def.allowIn.includes( contextItem.name ) ) { if ( contextItemIndex == 0 ) { return true; } else { const parentRule = this.getDefinition( contextItem ); return this._checkContextMatch( parentRule, context, contextItemIndex - 1 ); } } else { return false; } } } mix( Schema, ObservableMixin ); /** * Event fired when the {@link #checkChild} method is called. It allows plugging in * additional behavior – e.g. implementing rules which cannot be defined using the declarative * {@link module:engine/model/schema~SchemaItemDefinition} interface. * * **Note:** The {@link #addChildCheck} method is a more handy way to register callbacks. Internally, * it registers a listener to this event but comes with a simpler API and it is the recommended choice * in most of the cases. * * The {@link #checkChild} method fires an event because it is * {@link module:utils/observablemixin~ObservableMixin#decorate decorated} with it. Thanks to that you can * use this event in a various way, but the most important use case is overriding standard behaviour of the * `checkChild()` method. Let's see a typical listener template: * * schema.on( 'checkChild', ( evt, args ) => { * const context = args[ 0 ]; * const childDefinition = args[ 1 ]; * }, { priority: 'high' } ); * * The listener is added with a `high` priority to be executed before the default method is really called. The `args` callback * parameter contains arguments passed to `checkChild( context, child )`. However, the `context` parameter is already * normalized to a {@link module:engine/model/schema~SchemaContext} instance and `child` to a * {@link module:engine/model/schema~SchemaCompiledItemDefinition} instance, so you don't have to worry about * the various ways how `context` and `child` may be passed to `checkChild()`. * * **Note:** `childDefinition` may be `undefined` if `checkChild()` was called with a non-registered element. * * So, in order to implement a rule "disallow `heading1` in `blockQuote`" you can add such a listener: * * schema.on( 'checkChild', ( evt, args ) => { * const context = args[ 0 ]; * const childDefinition = args[ 1 ]; * * if ( context.endsWith( 'blockQuote' ) && childDefinition && childDefinition.name == 'heading1' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkChild()'s return value. * evt.return = false; * } * }, { priority: 'high' } ); * * Allowing elements in specific contexts will be a far less common use case, because it's normally handled by * `allowIn` rule from {@link module:engine/model/schema~SchemaItemDefinition} but if you have a complex scenario * where `listItem` should be allowed only in element `foo` which must be in element `bar`, then this would be the way: * * schema.on( 'checkChild', ( evt, args ) => { * const context = args[ 0 ]; * const childDefinition = args[ 1 ]; * * if ( context.endsWith( 'bar foo' ) && childDefinition.name == 'listItem' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkChild()'s return value. * evt.return = true; * } * }, { priority: 'high' } ); * * @event checkChild * @param {Array} args The `checkChild()`'s arguments. */ /** * Event fired when the {@link #checkAttribute} method is called. It allows plugging in * additional behavior – e.g. implementing rules which cannot be defined using the declarative * {@link module:engine/model/schema~SchemaItemDefinition} interface. * * **Note:** The {@link #addAttributeCheck} method is a more handy way to register callbacks. Internally, * it registers a listener to this event but comes with a simpler API and it is the recommended choice * in most of the cases. * * The {@link #checkAttribute} method fires an event because it's * {@link module:utils/observablemixin~ObservableMixin#decorate decorated} with it. Thanks to that you can * use this event in a various way, but the most important use case is overriding standard behaviour of the * `checkAttribute()` method. Let's see a typical listener template: * * schema.on( 'checkAttribute', ( evt, args ) => { * const context = args[ 0 ]; * const attributeName = args[ 1 ]; * }, { priority: 'high' } ); * * The listener is added with a `high` priority to be executed before the default method is really called. The `args` callback * parameter contains arguments passed to `checkAttribute( context, attributeName )`. However, the `context` parameter is already * normalized to a {@link module:engine/model/schema~SchemaContext} instance, so you don't have to worry about * the various ways how `context` may be passed to `checkAttribute()`. * * So, in order to implement a rule "disallow `bold` in a text which is in a `heading1` you can add such a listener: * * schema.on( 'checkAttribute', ( evt, args ) => { * const context = args[ 0 ]; * const atributeName = args[ 1 ]; * * if ( context.endsWith( 'heading1 $text' ) && attributeName == 'bold' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkAttribute()'s return value. * evt.return = false; * } * }, { priority: 'high' } ); * * Allowing attributes in specific contexts will be a far less common use case, because it's normally handled by * `allowAttributes` rule from {@link module:engine/model/schema~SchemaItemDefinition} but if you have a complex scenario * where `bold` should be allowed only in element `foo` which must be in element `bar`, then this would be the way: * * schema.on( 'checkAttribute', ( evt, args ) => { * const context = args[ 0 ]; * const atributeName = args[ 1 ]; * * if ( context.endsWith( 'bar foo $text' ) && attributeName == 'bold' ) { * // Prevent next listeners from being called. * evt.stop(); * // Set the checkAttribute()'s return value. * evt.return = true; * } * }, { priority: 'high' } ); * * @event checkAttribute * @param {Array} args The `checkAttribute()`'s arguments. */ /** * A definition of a {@link module:engine/model/schema~Schema schema} item. * * You can define the following rules: * * * `allowIn` – A string or an array of strings. Defines in which other items this item will be allowed. * * `allowAttributes` – A string or an array of strings. Defines allowed attributes of the given item. * * `allowContentOf` – A string or an array of strings. Inherits "allowed children" from other items. * * `allowWhere` – A string or an array of strings. Inherits "allowed in" from other items. * * `allowAttributesOf` – A string or an array of strings. Inherits attributes from other items. * * `inheritTypesFrom` – A string or an array of strings. Inherits `is*` properties of other items. * * `inheritAllFrom` – A string. A shorthand for `allowContentOf`, `allowWhere`, `allowAttributesOf`, `inheritTypesFrom`. * * Additionally, you can define the following `is*` properties: `isBlock`, `isLimit`, `isObject`. Read about them below. * * # The is* properties * * There are 3 commonly used `is*` properties. Their role is to assign additional semantics to schema items. * You can define more properties but you will also need to implement support for them in the existing editor features. * * * `isBlock` – Whether this item is paragraph-like. Generally speaking, content is usually made out of blocks * like paragraphs, list items, images, headings, etc. All these elements are marked as blocks. A block * should not allow another block inside. Note: There is also the `$block` generic item which has `isBlock` set to `true`. * Most block type items will inherit from `$block` (through `inheritAllFrom`). * * `isLimit` – It can be understood as whether this element should not be split by Enter. * Examples of limit elements: `$root`, table cell, image caption, etc. In other words, all actions that happen inside * a limit element are limited to its content. **Note:** All objects (`isObject`) are treated as limit elements, too. * * `isObject` – Whether an item is "self-contained" and should be treated as a whole. Examples of object elements: * `image`, `table`, `video`, etc. **Note:** An object is also a limit, so * {@link module:engine/model/schema~Schema#isLimit `isLimit()`} * returns `true` for object elements automatically. * * # Generic items * * There are three basic generic items: `$root`, `$block` and `$text`. * They are defined as follows: * * this.schema.register( '$root', { * isLimit: true * } ); * this.schema.register( '$block', { * allowIn: '$root', * isBlock: true * } ); * this.schema.register( '$text', { * allowIn: '$block' * } ); * * They reflect typical editor content that is contained within one root, consists of several blocks * (paragraphs, lists items, headings, images) which, in turn, may contain text inside. * * By inheriting from the generic items you can define new items which will get extended by other editor features. * Read more about generic types in the {@linkTODO Defining schema} guide. * * # Example definitions * * Allow `paragraph` in roots and block quotes: * * schema.register( 'paragraph', { * allowIn: [ '$root', 'blockQuote' ], * isBlock: true * } ); * * Allow `paragraph` everywhere where `$block` is allowed (i.e. in `$root`): * * schema.register( 'paragraph', { * allowWhere: '$block', * isBlock: true * } ); * * Make `image` a block object, which is allowed everywhere where `$block` is. * Also, allow `src` and `alt` attributes in it: * * schema.register( 'image', { * allowWhere: '$block', * allowAttributes: [ 'src', 'alt' ], * isBlock: true, * isObject: true * } ); * * Make `caption` allowed in `image` and make it allow all the content of `$block`s (usually, `$text`). * Also, mark it as a limit element so it cannot be split: * * schema.register( 'caption', { * allowIn: 'image', * allowContentOf: '$block', * isLimit: true * } ); * * Make `listItem` inherit all from `$block` but also allow additional attributes: * * schema.register( 'listItem', { * inheritAllFrom: '$block', * allowAttributes: [ 'listType', 'listIndent' ] * } ); * * Which translates to: * * schema.register( 'listItem', { * allowWhere: '$block', * allowContentOf: '$block', * allowAttributesOf: '$block', * inheritTypesFrom: '$block', * allowAttributes: [ 'listType', 'listIndent' ] * } ); * * # Tips * * * Check schema definitions of existing features to see how they are defined. * * If you want to publish your feature so other developers can use it, try to use * generic items as much as possible. * * Keep your model clean. Limit it to the actual data and store information in a normalized way. * * Remember about definining the `is*` properties. They do not affect the allowed structures, but they can * affect how the editor features treat your elements. * * @typedef {Object} module:engine/model/schema~SchemaItemDefinition */ /** * A simplified version of {@link module:engine/model/schema~SchemaItemDefinition} after * compilation by the {@link module:engine/model/schema~Schema schema}. * Rules fed to the schema by {@link module:engine/model/schema~Schema#register} * and {@link module:engine/model/schema~Schema#extend} methods are defined in the * {@link module:engine/model/schema~SchemaItemDefinition} format. * Later on, they are compiled to `SchemaCompiledItemDefition` so when you use e.g. * the {@link module:engine/model/schema~Schema#getDefinition} method you get the compiled version. * * The compiled version contains only the following properties: * * * The `name` property, * * The `is*` properties, * * The `allowIn` array, * * The `allowAttributes` array. * * @typedef {Object} module:engine/model/schema~SchemaCompiledItemDefinition */ /** * A schema context — a list of ancestors of a given position in the document. * * Considering such position: * * <$root> *
* * ^ * *
* * * The context of this position is its {@link module:engine/model/position~Position#getAncestors lists of ancestors}: * * [ rootElement, blockQuoteElement, paragraphElement ] * * Contexts are used in the {@link module:engine/model/schema~Schema#event:checkChild `Schema#checkChild`} and * {@link module:engine/model/schema~Schema#event:checkAttribute `Schema#checkAttribute`} events as a definition * of a place in the document where the check occurs. The context instances are created based on the first arguments * of the {@link module:engine/model/schema~Schema#checkChild `Schema#checkChild()`} and * {@link module:engine/model/schema~Schema#checkAttribute `Schema#checkAttribute()`} methods so when * using these methods you need to use {@link module:engine/model/schema~SchemaContextDefinition}s. */ export class SchemaContext { /** * Creates an instance of the context. * * @param {module:engine/model/schema~SchemaContextDefinition} context */ constructor( context ) { if ( context instanceof SchemaContext ) { return context; } if ( typeof context == 'string' ) { context = [ context ]; } else if ( !Array.isArray( context ) ) { // `context` is item or position. // Position#getAncestors() doesn't accept any parameters but it works just fine here. context = context.getAncestors( { includeSelf: true } ); } if ( context[ 0 ] && typeof context[ 0 ] != 'string' && context[ 0 ].is( 'documentFragment' ) ) { context.shift(); } this._items = context.map( mapContextItem ); } /** * The number of items. * * @type {Number} */ get length() { return this._items.length; } /** * The last item (the lowest node). * * @type {module:engine/model/schema~SchemaContextItem} */ get last() { return this._items[ this._items.length - 1 ]; } /** * Iterable interface. * * Iterates over all context items. * * @returns {Iterable.} */ [ Symbol.iterator ]() { return this._items[ Symbol.iterator ](); } /** * Returns a new schema context instance with an additional item. * * Item can be added as: * * const context = new SchemaContext( [ '$root' ] ); * * // An element. * const fooElement = writer.createElement( 'fooElement' ); * const newContext = context.push( fooElement ); // [ '$root', 'fooElement' ] * * // A text node. * const text = writer.createText( 'foobar' ); * const newContext = context.push( text ); // [ '$root', '$text' ] * * // A string (element name). * const newContext = context.push( 'barElement' ); // [ '$root', 'barElement' ] * * **Note** {module:engine/model/node~Node} that is already in the model tree will be added as the only item (without ancestors). * * @param {String|module:engine/model/node~Node|Array} item An item that will be added * to the current context. * @returns {module:engine/model/schema~SchemaContext} A new schema context instance with an additional item. */ push( item ) { const ctx = new SchemaContext( [ item ] ); ctx._items = [ ...this._items, ...ctx._items ]; return ctx; } /** * Gets an item on the given index. * * @returns {module:engine/model/schema~SchemaContextItem} */ getItem( index ) { return this._items[ index ]; } /** * Returns the names of items. * * @returns {Iterable.} */ * getNames() { yield* this._items.map( item => item.name ); } /** * Checks whether the context ends with the given nodes. * * const ctx = new SchemaContext( [ rootElement, paragraphElement, textNode ] ); * * ctx.endsWith( '$text' ); // -> true * ctx.endsWith( 'paragraph $text' ); // -> true * ctx.endsWith( '$root' ); // -> false * ctx.endsWith( 'paragraph' ); // -> false * * @param {String} query * @returns {Boolean} */ endsWith( query ) { return Array.from( this.getNames() ).join( ' ' ).endsWith( query ); } } /** * The definition of a {@link module:engine/model/schema~SchemaContext schema context}. * * Contexts can be created in multiple ways: * * * By defining a **node** – in this cases this node and all its ancestors will be used. * * By defining a **position** in the document – in this case all its ancestors will be used. * * By defining an **array of nodes** – in this case this array defines the entire context. * * By defining a **name of node** - in this case node will be "mocked". It is not recommended because context * will be unrealistic (e.g. attributes of these nodes are not specified). However, at times this may be the only * way to define the context (e.g. when checking some hypothetical situation). * * By defining an **array of node names** (potentially, mixed with real nodes) – The same as **name of node** * but it is possible to create a path. * * By defining a {@link module:engine/model/schema~SchemaContext} instance - in this case the same instance as provided * will be return. * * Examples of context definitions passed to the {@link module:engine/model/schema~Schema#checkChild `Schema#checkChild()`} * method: * * // Assuming that we have a $root > blockQuote > paragraph structure, the following code * // will check node 'foo' in the following context: * // [ rootElement, blockQuoteElement, paragraphElement ] * const contextDefinition = paragraphElement; * const childToCheck = 'foo'; * schema.checkChild( contextDefinition, childToCheck ); * * // Also check in [ rootElement, blockQuoteElement, paragraphElement ]. * schema.checkChild( Position.createAt( paragraphElement ), 'foo' ); * * // Check in [ rootElement, paragraphElement ]. * schema.checkChild( [ rootElement, paragraphElement ], 'foo' ); * * // Check only fakeParagraphElement. * schema.checkChild( 'paragraph', 'foo' ); * * // Check in [ fakeRootElement, fakeBarElement, paragraphElement ]. * schema.checkChild( [ '$root', 'bar', paragraphElement ], 'foo' ); * * All these `checkChild()` calls will fire {@link module:engine/model/schema~Schema#event:checkChild `Schema#checkChild`} * events in which `args[ 0 ]` is an instance of the context. Therefore, you can write a listener like this: * * schema.on( 'checkChild', ( evt, args ) => { * const ctx = args[ 0 ]; * * console.log( Array.from( ctx.getNames() ) ); * } ); * * Which will log the following: * * [ '$root', 'blockQuote', 'paragraph' ] * [ '$root', 'paragraph' ] * [ '$root', 'bar', 'paragraph' ] * * Note: When using the {@link module:engine/model/schema~Schema#checkAttribute `Schema#checkAttribute()`} method * you may want to check whether a text node may have an attribute. A {@link module:engine/model/text~Text} is a * correct way to define a context so you can do this: * * schema.checkAttribute( textNode, 'bold' ); * * But sometimes you want to check whether a text at a given position might've had some attribute, * in which case you can create a context by mising an array of elements with a `'$text'` string: * * // Check in [ rootElement, paragraphElement, textNode ]. * schema.checkChild( [ ...positionInParagraph.getAncestors(), '$text' ], 'bold' ); * * @typedef {module:engine/model/node~Node|module:engine/model/position~Position|module:engine/model/schema~SchemaContext| * String|Array.} module:engine/model/schema~SchemaContextDefinition */ /** * An item of the {@link module:engine/model/schema~SchemaContext schema context}. * * It contains 3 properties: * * * `name` – the name of this item, * * `* getAttributeKeys()` – a generator of keys of item attributes, * * `getAttribute( keyName )` – a method to get attribute values. * * The context item interface is a highly simplified version of {@link module:engine/model/node~Node} and its role * is to expose only the information which schema checks are able to provide (which is the name of the node and * node's attributes). * * schema.on( 'checkChild', ( evt, args ) => { * const ctx = args[ 0 ]; * const firstItem = ctx.getItem( 0 ); * * console.log( firstItem.name ); // -> '$root' * console.log( firstItem.getAttribute( 'foo' ) ); // -> 'bar' * console.log( Array.from( firstItem.getAttributeKeys() ) ); // -> [ 'foo', 'faa' ] * } ); * * @typedef {Object} module:engine/model/schema~SchemaContextItem */ function compileBaseItemRule( sourceItemRules, itemName ) { const itemRule = { name: itemName, allowIn: [], allowContentOf: [], allowWhere: [], allowAttributes: [], allowAttributesOf: [], inheritTypesFrom: [] }; copyTypes( sourceItemRules, itemRule ); copyProperty( sourceItemRules, itemRule, 'allowIn' ); copyProperty( sourceItemRules, itemRule, 'allowContentOf' ); copyProperty( sourceItemRules, itemRule, 'allowWhere' ); copyProperty( sourceItemRules, itemRule, 'allowAttributes' ); copyProperty( sourceItemRules, itemRule, 'allowAttributesOf' ); copyProperty( sourceItemRules, itemRule, 'inheritTypesFrom' ); makeInheritAllWork( sourceItemRules, itemRule ); return itemRule; } function compileAllowContentOf( compiledDefinitions, itemName ) { for ( const allowContentOfItemName of compiledDefinitions[ itemName ].allowContentOf ) { // The allowContentOf property may point to an unregistered element. if ( compiledDefinitions[ allowContentOfItemName ] ) { const allowedChildren = getAllowedChildren( compiledDefinitions, allowContentOfItemName ); allowedChildren.forEach( allowedItem => { allowedItem.allowIn.push( itemName ); } ); } } delete compiledDefinitions[ itemName ].allowContentOf; } function compileAllowWhere( compiledDefinitions, itemName ) { for ( const allowWhereItemName of compiledDefinitions[ itemName ].allowWhere ) { const inheritFrom = compiledDefinitions[ allowWhereItemName ]; // The allowWhere property may point to an unregistered element. if ( inheritFrom ) { const allowedIn = inheritFrom.allowIn; compiledDefinitions[ itemName ].allowIn.push( ...allowedIn ); } } delete compiledDefinitions[ itemName ].allowWhere; } function compileAllowAttributesOf( compiledDefinitions, itemName ) { for ( const allowAttributeOfItem of compiledDefinitions[ itemName ].allowAttributesOf ) { const inheritFrom = compiledDefinitions[ allowAttributeOfItem ]; if ( inheritFrom ) { const inheritAttributes = inheritFrom.allowAttributes; compiledDefinitions[ itemName ].allowAttributes.push( ...inheritAttributes ); } } delete compiledDefinitions[ itemName ].allowAttributesOf; } function compileInheritPropertiesFrom( compiledDefinitions, itemName ) { const item = compiledDefinitions[ itemName ]; for ( const inheritPropertiesOfItem of item.inheritTypesFrom ) { const inheritFrom = compiledDefinitions[ inheritPropertiesOfItem ]; if ( inheritFrom ) { const typeNames = Object.keys( inheritFrom ).filter( name => name.startsWith( 'is' ) ); for ( const name of typeNames ) { if ( !( name in item ) ) { item[ name ] = inheritFrom[ name ]; } } } } delete item.inheritTypesFrom; } // Remove items which weren't registered (because it may break some checks or we'd need to complicate them). // Make sure allowIn doesn't contain repeated values. function cleanUpAllowIn( compiledDefinitions, itemName ) { const itemRule = compiledDefinitions[ itemName ]; const existingItems = itemRule.allowIn.filter( itemToCheck => compiledDefinitions[ itemToCheck ] ); itemRule.allowIn = Array.from( new Set( existingItems ) ); } function cleanUpAllowAttributes( compiledDefinitions, itemName ) { const itemRule = compiledDefinitions[ itemName ]; itemRule.allowAttributes = Array.from( new Set( itemRule.allowAttributes ) ); } function copyTypes( sourceItemRules, itemRule ) { for ( const sourceItemRule of sourceItemRules ) { const typeNames = Object.keys( sourceItemRule ).filter( name => name.startsWith( 'is' ) ); for ( const name of typeNames ) { itemRule[ name ] = sourceItemRule[ name ]; } } } function copyProperty( sourceItemRules, itemRule, propertyName ) { for ( const sourceItemRule of sourceItemRules ) { if ( typeof sourceItemRule[ propertyName ] == 'string' ) { itemRule[ propertyName ].push( sourceItemRule[ propertyName ] ); } else if ( Array.isArray( sourceItemRule[ propertyName ] ) ) { itemRule[ propertyName ].push( ...sourceItemRule[ propertyName ] ); } } } function makeInheritAllWork( sourceItemRules, itemRule ) { for ( const sourceItemRule of sourceItemRules ) { const inheritFrom = sourceItemRule.inheritAllFrom; if ( inheritFrom ) { itemRule.allowContentOf.push( inheritFrom ); itemRule.allowWhere.push( inheritFrom ); itemRule.allowAttributesOf.push( inheritFrom ); itemRule.inheritTypesFrom.push( inheritFrom ); } } } function getAllowedChildren( compiledDefinitions, itemName ) { const itemRule = compiledDefinitions[ itemName ]; return getValues( compiledDefinitions ).filter( def => def.allowIn.includes( itemRule.name ) ); } function getValues( obj ) { return Object.keys( obj ).map( key => obj[ key ] ); } function mapContextItem( ctxItem ) { if ( typeof ctxItem == 'string' ) { return { name: ctxItem, * getAttributeKeys() {}, getAttribute() {} }; } else { return { // '$text' means text nodes and text proxies. name: ctxItem.is( 'element' ) ? ctxItem.name : '$text', * getAttributeKeys() { yield* ctxItem.getAttributeKeys(); }, getAttribute( key ) { return ctxItem.getAttribute( key ); } }; } } // Generator function returning values from provided walkers, switching between them at each iteration. If only one walker // is provided it will return data only from that walker. // // @param {module:engine/module/treewalker~TreeWalker} [backward] Walker iterating in backward direction. // @param {module:engine/module/treewalker~TreeWalker} [forward] Walker iterating in forward direction. // @returns {Iterable.} Object returned at each iteration contains `value` and `walker` (informing which walker returned // given value) fields. function* combineWalkers( backward, forward ) { let done = false; while ( !done ) { done = true; if ( backward ) { const step = backward.next(); if ( !step.done ) { done = false; yield { walker: backward, value: step.value }; } } if ( forward ) { const step = forward.next(); if ( !step.done ) { done = false; yield { walker: forward, value: step.value }; } } } }