Duplicate CSS written under media queries

GrapeJs Editor Initialization

var editor = grapesjs.init({
	showOffsets: 1,
	noticeOnUnload: 0,
	container: '#gjs',
	height: '100%',
	fromElement: true,
	storageManager: { autoload: 0 },
	styleManager: {
		sectors: [
			{
				name: 'General',
				open: false,
				buildProps: ['float', 'display', 'position', 'top', 'right', 'left', 'bottom']
			}, {
				name: 'Dimension',
				open: false,
				buildProps: ['width', 'height', 'max-width', 'min-height', 'margin', 'padding'],
			}, {
				name: 'Typography',
				open: false,
				buildProps: ['font-family', 'font-size', 'font-weight', 'letter-spacing', 'color', 'line-height', 'text-shadow'],
			}, {
				name: 'Decorations',
				open: false,
				buildProps: ['border-radius-c', 'background-color', 'border-radius', 'border', 'box-shadow', 'background'],
			}, {
				name: 'Extra',
				open: false,
				buildProps: ['transition', 'perspective', 'transform'],
			}, {
				name: 'Flex',
				open: false,
				properties: [
					{
						name: 'Flex Container',
						property: 'display',
						type: 'select',
						defaults: 'block',
						list: [
							{ value: 'block', name: 'Disable' },
							{ value: 'flex', name: 'Enable' }
						],
					}, {
						name: 'Flex Parent',
						property: 'label-parent-flex',
						type: 'integer',
					}, {
						name: 'Direction',
						property: 'flex-direction',
						type: 'radio',
						defaults: 'row',
						list: [{
							value: 'row',
							name: 'Row',
							className: 'icons-flex icon-dir-row',
							title: 'Row',
						}, {
							value: 'row-reverse',
							name: 'Row reverse',
							className: 'icons-flex icon-dir-row-rev',
							title: 'Row reverse',
						}, {
							value: 'column',
							name: 'Column',
							title: 'Column',
							className: 'icons-flex icon-dir-col',
						}, {
							value: 'column-reverse',
							name: 'Column reverse',
							title: 'Column reverse',
							className: 'icons-flex icon-dir-col-rev',
						}],
					}, {
						name: 'Justify',
						property: 'justify-content',
						type: 'radio',
						defaults: 'flex-start',
						list: [{
							value: 'flex-start',
							className: 'icons-flex icon-just-start',
							title: 'Start',
						}, {
							value: 'flex-end',
							title: 'End',
							className: 'icons-flex icon-just-end',
						}, {
							value: 'space-between',
							title: 'Space between',
							className: 'icons-flex icon-just-sp-bet',
						}, {
							value: 'space-around',
							title: 'Space around',
							className: 'icons-flex icon-just-sp-ar',
						}, {
							value: 'center',
							title: 'Center',
							className: 'icons-flex icon-just-sp-cent',
						}],
					}, {
						name: 'Align',
						property: 'align-items',
						type: 'radio',
						defaults: 'center',
						list: [{
							value: 'flex-start',
							title: 'Start',
							className: 'icons-flex icon-al-start',
						}, {
							value: 'flex-end',
							title: 'End',
							className: 'icons-flex icon-al-end',
						}, {
							value: 'stretch',
							title: 'Stretch',
							className: 'icons-flex icon-al-str',
						}, {
							value: 'center',
							title: 'Center',
							className: 'icons-flex icon-al-center',
						}],
					}, {
						name: 'Flex Children',
						property: 'label-parent-flex',
						type: 'integer',
					}, {
						name: 'Order',
						property: 'order',
						type: 'integer',
						defaults: 0,
						min: 0
					}, {
						name: 'Flex',
						property: 'flex',
						type: 'composite',
						properties: [{
							name: 'Grow',
							property: 'flex-grow',
							type: 'integer',
							defaults: 0,
							min: 0
						}, {
							name: 'Shrink',
							property: 'flex-shrink',
							type: 'integer',
							defaults: 0,
							min: 0
						}, {
							name: 'Basis',
							property: 'flex-basis',
							type: 'integer',
							units: ['px', '%', ''],
							unit: '',
							defaults: 'auto',
						}],
					}, {
						name: 'Align',
						property: 'align-self',
						type: 'radio',
						defaults: 'auto',
						list: [{
							value: 'auto',
							name: 'Auto',
						}, {
							value: 'flex-start',
							title: 'Start',
							className: 'icons-flex icon-al-start',
						}, {
							value: 'flex-end',
							title: 'End',
							className: 'icons-flex icon-al-end',
						}, {
							value: 'stretch',
							title: 'Stretch',
							className: 'icons-flex icon-al-str',
						}, {
							value: 'center',
							title: 'Center',
							className: 'icons-flex icon-al-center',
						}],
					}
				]
			}
		]
	}
});

Test Block Added

editor.on('load', function () {
	var $ = grapesjs.$;
	var pn = editor.Panels;

	// Load and show settings and style manager
	var openTmBtn = pn.getButton('views', 'open-tm');
	openTmBtn && openTmBtn.set('active', 1);
	var openSm = pn.getButton('views', 'open-sm');
	openSm && openSm.set('active', 1);

	// Add Settings Sector
	var traitsSector = $('<div class="gjs-sm-sector no-select">' +
		'<div class="gjs-sm-title"><span class="icon-settings fa fa-cog"></span> Settings</div>' +
		'<div class="gjs-sm-properties" style="display: none;"></div></div>');
	var traitsProps = traitsSector.find('.gjs-sm-properties');
	traitsProps.append($('.gjs-trt-traits'));
	$('.gjs-sm-sectors').before(traitsSector);
	traitsSector.find('.gjs-sm-title').on('click', function () {
		var traitStyle = traitsProps.get(0).style;
		var hidden = traitStyle.display == 'none';
		if (hidden) {
			traitStyle.display = 'block';
		} else {
			traitStyle.display = 'none';
		}
	});

	// Test Block
	editor.BlockManager.add('test', {
		label: 'test',
		category: 'Basic',
		attributes: { class: 'fa fa-header' },

		content: `
		<header data-gjs-type="default" data-gjs-droppable="true" class="custom-header">
			<p>Test</p>
		</header>
		<style>
			.custom-header {
				width: 100%;
				height: 70px;
				background-color: #414141;
				padding: 20px;
				color: #fff;
			}
			@media (max-width: 480px){
				.custom-header {
					background-color: red;
				}
			}
		</style>
		`
	});
})

Output

@artf I am trying to add a custom block and providing HTML/CSS of the block via content attribute. When I drop the block onto the canvas then Media Query CSS is added twice to DOM Element with class gjs-css-rules-480px . It only happens if I provide CSS via content attribute. If I added any CSS using the StyleManager then it is rendered only once. Seems like issue with parsing CSS when initializing any block.

Link to GrapeJS I am fetching - https://grapesjs.com/js/grapes.min.js?v0.14.33

In my debugging (might be wrong), in the file : ./src/css_composer/index.js When a rule is added

    /**
     * Add new rule to the collection, if not yet exists with the same selectors
     * @param {Array<Selector>} selectors Array of selectors
     * @param {String} state Css rule state
     * @param {String} width For which device this style is oriented
     * @param {Object} opts Other options for the rule
     * @return {Model}
     * @example
     * var sm = editor.SelectorManager;
     * var sel1 = sm.add('myClass1');
     * var sel2 = sm.add('myClass2');
     * var rule = cssComposer.add([sel1, sel2], 'hover');
     * rule.set('style', {
     *   width: '100px',
     *   color: '#fff',
     * });
     * */
    add: function add(selectors, state, width) {
      var opts = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : {};

      var s = state || '';
      var w = width || '';
      var opt = _extends({}, opts);
      var rule = this.get(selectors, s, w, opt);

      // do not create rules that were found before
      // unless this is an at-rule, for which multiple declarations
      // make sense (e.g. multiple `@font-type`s)
      if (rule && rule.config && !rule.config.atRuleType) {
        return rule;
      } else {
        opt.state = s;
        opt.mediaText = w;
        opt.selectors = '';
        rule = new CssRule(opt, c);
        rule.get('selectors').add(selectors);
        rules.add(rule);
        return rule;
      }
    },


    /**
     * Get the rule
     * @param {Array<Selector>} selectors Array of selectors
     * @param {String} state Css rule state
     * @param {String} width For which device this style is oriented
     * @param {Object} ruleProps Other rule props
     * @return  {Model|null}
     * @example
     * var sm = editor.SelectorManager;
     * var sel1 = sm.add('myClass1');
     * var sel2 = sm.add('myClass2');
     * var rule = cssComposer.get([sel1, sel2], 'hover');
     * // Update the style
     * rule.set('style', {
     *   width: '300px',
     *   color: '#000',
     * });
     * */
    get: function get(selectors, state, width, ruleProps) {
      var rule = null;
      rules.each(function (m) {
        if (rule) return;
        if (m.compare(selectors, state, width, ruleProps)) rule = m;
      });
      return rule;
    },

The rule is matched against existing rules, if not present then added else updated. Somehow, in the compare function it is not able to find the rule and which leads to adding it twice!

Thanks Yomesh, I'm investigating on this