wip: adding multi class by separator feature

src/compiler/compile/Component.ts

@@ -1348,29 +1348,32 @@ function process_component_options(component: Component, nodes) {
 				const { name } = attribute;
 
 				switch (name) {
+					case 'classSeparator':
 					case 'tag': {
 						const code = 'invalid-tag-attribute';
-						const message = `'tag' must be a string literal`;
-						const tag = get_value(attribute, code, message);
+						const message = `'${name}' must be a string literal`;
+						const value = get_value(attribute, code, message);
 
-						if (typeof tag !== 'string' && tag !== null)
+						if (typeof value !== 'string' && value !== null)
 							component.error(attribute, { code, message });
 
-						if (tag && !/^[a-zA-Z][a-zA-Z0-9]*-[a-zA-Z0-9-]+$/.test(tag)) {
-							component.error(attribute, {
-								code: `invalid-tag-property`,
-								message: `tag name must be two or more words joined by the '-' character`,
-							});
-						}
+						if (value === 'tag') {
+							if (value && !/^[a-zA-Z][a-zA-Z0-9]*-[a-zA-Z0-9-]+$/.test(value)) {
+								component.error(attribute, {
+									code: `invalid-tag-property`,
+									message: `tag name must be two or more words joined by the '-' character`,
+								});
+							}
 
-						if (tag && !component.compile_options.customElement) {
-							component.warn(attribute, {
-								code: 'missing-custom-element-compile-options',
-								message: `The 'tag' option is used when generating a custom element. Did you forget the 'customElement: true' compile option?`
-							});
+							if (value && !component.compile_options.customElement) {
+								component.warn(attribute, {
+									code: 'missing-custom-element-compile-options',
+									message: `The 'tag' option is used when generating a custom element. Did you forget the 'customElement: true' compile option?`
+								});
+							}
 						}
 
-						component_options.tag = tag;
+						component_options[name] = value;
 						break;
 					}
 

src/compiler/compile/index.ts

@@ -26,7 +26,8 @@ const valid_options = [
 	'css',
 	'loopGuardTimeout',
 	'preserveComments',
-	'preserveWhitespace'
+	'preserveWhitespace',
+	'classSeparator'
 ];
 
 function validate_options(options: CompileOptions, warnings: Warning[]) {

src/compiler/compile/render_dom/wrappers/Element/index.ts

@@ -26,6 +26,7 @@ import { Identifier } from 'estree';
 import EventHandler from './EventHandler';
 import { extract_names } from 'periscopic';
 import Action from '../../../nodes/Action';
+import Expression from '../../../nodes/shared/Expression';
 
 const events = [
 	{
@@ -876,31 +877,38 @@ export default class ElementWrapper extends Wrapper {
 		const has_spread = this.node.attributes.some(attr => attr.is_spread);
 		this.node.classes.forEach(class_directive => {
 			const { expression, name } = class_directive;
-			let snippet;
-			let dependencies;
-			if (expression) {
-				snippet = expression.manipulate(block);
-				dependencies = expression.dependencies;
-			} else {
-				snippet = name;
-				dependencies = new Set([name]);
-			}
-			const updater = b`@toggle_class(${this.var}, "${name}", ${snippet});`;
 
-			block.chunks.hydrate.push(updater);
+			name.split(this.renderer.options.classSeparator).forEach((split_name: string) => {
+				this.add_class(block, expression, split_name, has_spread);
+			});	
+		});
+	}
+
+	add_class(block: Block, expression: Expression, name: string, has_spread: boolean) {
+		let snippet;
+		let dependencies;
+		if (expression) {
+			snippet = expression.manipulate(block);
+			dependencies = expression.dependencies;
+		} else {
+			snippet = name;
+			dependencies = new Set([name]);
+		}
+		const updater = b`@toggle_class(${this.var}, "${name}", ${snippet});`;
 
-			if (has_spread) {
-				block.chunks.update.push(updater);
-			} else if ((dependencies && dependencies.size > 0) || this.class_dependencies.length) {
-				const all_dependencies = this.class_dependencies.concat(...dependencies);
-				const condition = block.renderer.dirty(all_dependencies);
+		block.chunks.hydrate.push(updater);
 
-				block.chunks.update.push(b`
-					if (${condition}) {
-						${updater}
-					}`);
-			}
-		});
+		if (has_spread) {
+			block.chunks.update.push(updater);
+		} else if ((dependencies && dependencies.size > 0) || this.class_dependencies.length) {
+			const all_dependencies = this.class_dependencies.concat(...dependencies);
+			const condition = block.renderer.dirty(all_dependencies);
+
+			block.chunks.update.push(b`
+				if (${condition}) {
+					${updater}
+				}`);
+		}
 	}
 
 	add_manual_style_scoping(block) {

src/compiler/compile/render_ssr/handlers/Element.ts

@@ -30,8 +30,22 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 
 	const class_expression_list = node.classes.map(class_directive => {
 		const { expression, name } = class_directive;
-		const snippet = expression ? expression.node : x`#ctx.${name}`; // TODO is this right?
-		return x`${snippet} ? "${name}" : ""`;
+
+		const name_has_separator = name.includes(options.classSeparator);
+
+		let parsed_name = name;
+		if (name_has_separator) {
+			parsed_name = `"${name.split(",").join(' ')}"`;
+		}
+
+		if (name_has_separator && expression) {
+			// TODO: we have a wrong scenario here, "class:one,two". We should treat this case, showing error?
+			return parsed_name;
+		}
+
+		const snippet = expression ? expression.node : x`#ctx.${name}`;
+
+		return x`${snippet} ? "${parsed_name}" : ""`;
 	});
 	if (node.needs_manual_style_scoping) {
 		class_expression_list.push(x`"${node.component.stylesheet.id}"`);

src/compiler/interfaces.ts

@@ -126,6 +126,8 @@ export interface CompileOptions {
 
 	preserveComments?: boolean;
 	preserveWhitespace?: boolean;
+
+	classSeparator?: string;
 }
 
 export interface ParserOptions {

test/runtime/index.js

@@ -79,6 +79,7 @@ describe("runtime", () => {
 			compileOptions.hydratable = hydrate;
 			compileOptions.immutable = config.immutable;
 			compileOptions.accessors = 'accessors' in config ? config.accessors : true;
+			compileOptions.classSeparator = 'classSeparator' in config ? config.classSeparator : undefined;
 
 			cleanRequireCache();
 

test/runtime/samples/class-separation-boolean/_config.js

@@ -0,0 +1,6 @@
+export default {
+	classSeparator: ',',
+	skip_if_ssr: true,
+
+	html: `<div class="one two"></div>`,
+};

test/runtime/samples/class-separation-boolean/main.svelte

@@ -0,0 +1 @@
+<div class:one,two={true} />