[v3] Fix issue where class directives wouldn't work with spread props and class prop

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

@@ -548,16 +548,20 @@ export default class ElementWrapper extends Wrapper {
 	}
 
 	add_attributes(block: Block) {
+		// Get all the class dependencies first
+		this.attributes.forEach((attribute) => {
+			if (attribute.node.name === 'class' && attribute.node.is_dynamic) {
+				this.class_dependencies.push(...attribute.node.dependencies);
+			}
+		});
+
 		// @ts-ignore todo:
 		if (this.node.attributes.find(attr => attr.type === 'Spread')) {
 			this.add_spread_attributes(block);
 			return;
 		}
 
 		this.attributes.forEach((attribute) => {
-			if (attribute.node.name === 'class' && attribute.node.is_dynamic) {
-				this.class_dependencies.push(...attribute.node.dependencies);
-			}
 			attribute.render(block);
 		});
 	}

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

@@ -109,6 +109,9 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 				) {
 					// a boolean attribute with one non-Text chunk
 					args.push(`{ ${quote_name_if_necessary(attribute.name)}: ${snip(attribute.chunks[0])} }`);
+				} else if (attribute.name === 'class' && class_expression) {
+					// Add class expression
+					args.push(`{ ${quote_name_if_necessary(attribute.name)}: [\`${stringify_attribute(attribute, true)}\`, \`\${${class_expression}}\`].join(' ').trim() }`);
 				} else {
 					args.push(`{ ${quote_name_if_necessary(attribute.name)}: \`${stringify_attribute(attribute, true)}\` }`);
 				}

test/runtime/samples/class-with-dynamic-attribute-and-spread/_config.js

@@ -0,0 +1,21 @@
+export default {
+	props: {
+		myClass: 'one two',
+		attributes: {
+			role: 'button'
+		}
+	},
+
+	html: `<div class="one two three" role="button"></div>`,
+
+	test({ assert, component, target, window }) {
+		component.myClass = 'one';
+		component.attributes = {
+			'aria-label': 'Test'
+		};
+
+		assert.htmlEqual(target.innerHTML, `
+			<div class="one three" aria-label="Test"></div>
+		`);
+	}
+};

test/runtime/samples/class-with-dynamic-attribute-and-spread/main.svelte

@@ -0,0 +1,6 @@
+<script>
+	export let myClass;
+	export let attributes = {};
+</script>
+
+<div class={myClass} class:three={true} {...attributes}></div>

test/runtime/samples/class-with-spread/_config.js

@@ -0,0 +1,21 @@
+export default {
+	props: {
+		myClass: 'one two',
+		attributes: {
+			role: 'button'
+		}
+	},
+
+	html: `<div class="one two" role="button"></div>`,
+
+	test({ assert, component, target, window }) {
+		component.myClass = 'one';
+		component.attributes = {
+			'aria-label': 'Test'
+		};
+
+		assert.htmlEqual(target.innerHTML, `
+			<div class="one" aria-label="Test"></div>
+		`);
+	}
+};

test/runtime/samples/class-with-spread/main.svelte

@@ -0,0 +1,6 @@
+<script>
+	export let myClass;
+	export let attributes = {};
+</script>
+
+<div class={myClass} {...attributes}></div>