Added DataProcessor#useFillerType(). Added `GFMDataProcessor#useFil…

…lerType()`.

packages/ckeditor5-engine/src/dataprocessor/dataprocessor.jsdoc

@@ -49,3 +49,16 @@
  * @param {module:engine/view/matcher~MatcherPattern} pattern Pattern matching all view elements whose content should
  * be treated as plain text.
  */
+
+/**
+ * If the processor is set to use marked fillers, it will insert nbsp fillers wrapped in spans
+ * (`<span data-cke-filler="true">&nbsp;</span>`), instead of regular nbsp characters (`&nbsp;`).
+ *
+ * This mode allows for more precise handling of block fillers (so they don't leak into editor content) but bloats the editor
+ * data with additional markup.
+ *
+ * This mode may be required by some features and will be turned on by them automatically.
+ *
+ * @method #useFillerType
+ * @param {'default'|'marked'} type Whether to use default or marked nbsp block fillers.
+ */

packages/ckeditor5-markdown-gfm/src/gfmdataprocessor.js

@@ -83,4 +83,10 @@ export default class GFMDataProcessor {
 	registerRawContentMatcher( pattern ) {
 		this._htmlDP.registerRawContentMatcher( pattern );
 	}
+
+	/**
+	 * This method does not have an effect on data processor result. It exists for compatibility with
+	 * {@link module:engine/dataprocessor/dataprocessor~DataProcessor `DataProcessor` interface}.
+	 */
+	useFillerType() {}
 }

packages/ckeditor5-markdown-gfm/tests/gfmdataprocessor/gfmdataprocessor.js

@@ -0,0 +1,25 @@
+/**
+ * @license Copyright (c) 2003-2021, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
+ */
+
+import GFMDataProcessor from '../../src/gfmdataprocessor';
+import ViewDocument from '@ckeditor/ckeditor5-engine/src/view/document';
+import { StylesProcessor } from '@ckeditor/ckeditor5-engine/src/view/stylesmap';
+
+describe( 'GFMDataProcessor', () => {
+	let dataProcessor, viewDocument;
+
+	beforeEach( () => {
+		viewDocument = new ViewDocument( new StylesProcessor() );
+		dataProcessor = new GFMDataProcessor( viewDocument );
+	} );
+
+	describe( 'useFillerType()', () => {
+		it( 'should have this method to be compatible with `DataProcessor` interface', () => {
+			expect( () => {
+				dataProcessor.useFillerType( 'default' );
+			} ).not.to.throw();
+		} );
+	} );
+} );