[WIP] sveltejs#1748 - Custom elements light dom, open / closed

Author: Cris Ward

src/compiler/compile/Component.ts

@@ -14,7 +14,7 @@ import Stylesheet from './css/Stylesheet';
 import { test } from '../config';
 import Fragment from './nodes/Fragment';
 import internal_exports from './internal_exports';
-import { Ast, CompileOptions, Var, Warning, CssResult } from '../interfaces';
+import { Ast, CompileOptions, Var, Warning, CssResult, ShadowDomMode } from '../interfaces';
 import error from '../utils/error';
 import get_code_frame from '../utils/get_code_frame';
 import flatten_reference from './utils/flatten_reference';
@@ -30,6 +30,7 @@ import check_graph_for_cycles from './utils/check_graph_for_cycles';
 import { print, x, b } from 'code-red';
 
 interface ComponentOptions {
+	shadowdom?: ShadowDomMode;
 	namespace?: string;
 	tag?: string;
 	immutable?: boolean;
@@ -158,6 +159,7 @@ export default class Component {
 				});
 			}
 			this.tag = this.component_options.tag || compile_options.tag;
+			this.compile_options.shadowDom = this.component_options.shadowdom || "open";
 		} else {
 			this.tag = this.name.name;
 		}
@@ -170,7 +172,7 @@ export default class Component {
 
 		this.walk_instance_js_post_template();
 
-		if (!compile_options.customElement) this.stylesheet.reify();
+		if (!compile_options.customElement || compile_options.shadowDom=="none") this.stylesheet.reify();
 
 		this.stylesheet.warn_on_unused_selectors(this);
 	}
@@ -1414,7 +1416,16 @@ function process_component_options(component: Component, nodes) {
 						component_options[name] = value;
 						break;
 					}
+					case 'shadowdom':{
+						const code = 'invalid-shadowdom-attribute';
+						const message = `'shadowdom' must be set to 'open', 'closed or 'none'`;
+						const value = get_value(attribute, code, message)
+						if(value != "open" && value != "none" && value != "closed")
+							component.error(attribute, { code, message });
 
+						component_options[name] = value;
+						break;
+					}
 					default:
 						component.error(attribute, {
 							code: `invalid-options-attribute`,

src/compiler/compile/index.ts

@@ -22,6 +22,7 @@ const valid_options = [
 	'hydratable',
 	'legacy',
 	'customElement',
+	'shadowDom',
 	'tag',
 	'css',
 	'loopGuardTimeout',

src/compiler/compile/render_dom/index.ts

@@ -20,7 +20,7 @@ export default function dom(
 	block.has_outro_method = true;
 
 	// prevent fragment being created twice (#1063)
-	if (options.customElement) block.chunks.create.push(b`this.c = @noop;`);
+	if (options.customElement && options.shadowDom !== "none") block.chunks.create.push(b`this.c = @noop;`);
 
 	const body = [];
 
@@ -29,17 +29,17 @@ export default function dom(
 		body.push(b`const ${renderer.file_var} = ${file};`);
 	}
 
-	const css = component.stylesheet.render(options.filename, !options.customElement);
+	const css = component.stylesheet.render(options.filename, (!options.customElement || options.shadowDom === "none"));
 	const styles = component.stylesheet.has_styles && options.dev
 		? `${css.code}\n/*# sourceMappingURL=${css.map.toUrl()} */`
 		: css.code;
 
 	const add_css = component.get_unique_name('add_css');
 
 	const should_add_css = (
-		!options.customElement &&
+		(!options.customElement  &&
 		!!styles &&
-		options.css !== false
+		options.css !== false ) || options.shadowDom === "none"
 	);
 
 	if (should_add_css) {
@@ -437,14 +437,19 @@ export default function dom(
 	}
 
 	if (options.customElement) {
+		const lightDom = options.shadowDom === 'none';
 		const declaration = b`
 			class ${name} extends @SvelteElement {
 				constructor(options) {
 					super();
+					${!lightDom && b`
+						this._root =this.attachShadow({ mode: '${options.shadowDom}' });
+					`}
 
-					${css.code && b`this.shadowRoot.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
+					${css.code && !lightDom && b`this._root.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
+					${should_add_css && lightDom && b`if (!@_document.getElementById("${component.stylesheet.id}-style")) ${add_css}();`}
 
-					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
+					@init(this, { target: ${lightDom ? 'this' : 'this._root'} }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
 
 					${dev_props_check}
 

src/compiler/interfaces.ts

@@ -120,6 +120,7 @@ export interface CompileOptions {
 	hydratable?: boolean;
 	legacy?: boolean;
 	customElement?: boolean;
+	shadowDom?: ShadowDomMode;
 	tag?: string;
 	css?: boolean;
 	loopGuardTimeout?: number;
@@ -166,4 +167,8 @@ export interface Var {
 export interface CssResult { 
 	code: string;
 	map: SourceMap;
-}
+}
+
+export type ShadowDomMode = 'none'
+	| 'open'
+	| 'closed'

src/runtime/internal/Component.ts

@@ -167,7 +167,6 @@ if (typeof HTMLElement === 'function') {
 		$$: T$$;
 		constructor() {
 			super();
-			this.attachShadow({ mode: 'open' });
 		}
 
 		connectedCallback() {

test/js/samples/css-shadow-dom-keyframes/expected.js

@@ -33,6 +33,7 @@ function create_fragment(ctx) {
 class Component extends SvelteElement {
 	constructor(options) {
 		super();
+		this.attachShadow({ mode: "open" });
 		this.shadowRoot.innerHTML = `<style>div{animation:foo 1s}@keyframes foo{0%{opacity:0}100%{opacity:1}}</style>`;
 		init(this, { target: this.shadowRoot }, null, create_fragment, safe_not_equal, {});