cache animation param

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

@@ -851,7 +851,21 @@ export default class ElementWrapper extends Wrapper {
 			${outro && b`@add_transform(${this.var}, ${rect});`}
 		`);
 
-		const params = this.node.animation.expression ? this.node.animation.expression.manipulate(block) : x`{}`;
+		let params;
+		if (this.node.animation.expression) {
+			params = this.node.animation.expression.manipulate(block);
+
+			if (this.node.animation.expression.dynamic_dependencies().length) {
+				// if `params` is dynamic, calculate params ahead of time in the `.r()` method
+				const params_var = block.get_unique_name('params');
+				block.add_variable(params_var);
+
+				block.chunks.measure.push(b`${params_var} = ${params};`);
+				params = params_var;
+			}
+		} else {
+			params = x`{}`;
+		}
 
 		const name = this.renderer.reference(this.node.animation.name);
 

test/js/samples/each-block-keyed-animated/expected.js

@@ -43,7 +43,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(ctx, dirty) {
+		p(new_ctx, dirty) {
+			ctx = new_ctx;
 			if (dirty & /*things*/ 1 && t_value !== (t_value = /*thing*/ ctx[1].name + "")) set_data(t, t_value);
 		},
 		r() {

test/js/samples/each-block-keyed/expected.js

@@ -39,7 +39,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(ctx, dirty) {
+		p(new_ctx, dirty) {
+			ctx = new_ctx;
 			if (dirty & /*things*/ 1 && t_value !== (t_value = /*thing*/ ctx[1].name + "")) set_data(t, t_value);
 		},
 		d(detaching) {

test/runtime/samples/animation-js-delay/_config.js

@@ -56,5 +56,29 @@ export default {
 		raf.tick(150);
 		assert.equal(divs[0].dy, 0);
 		assert.equal(divs[4].dy, 0);
+
+		component.things = [
+			{ id: 1, name: 'a' },
+			{ id: 2, name: 'b' },
+			{ id: 3, name: 'c' },
+			{ id: 4, name: 'd' },
+			{ id: 5, name: 'e' }
+		];
+
+		divs = document.querySelectorAll('div');
+		assert.equal(divs[0].dy, 120);
+		assert.equal(divs[4].dy, -120);
+
+		raf.tick(200);
+		assert.equal(divs[0].dy, 108);
+		assert.equal(divs[4].dy, -60);
+
+		raf.tick(250);
+		assert.equal(divs[0].dy, 48);
+		assert.equal(divs[4].dy, 0);
+
+		raf.tick(300);
+		assert.equal(divs[0].dy, 0);
+		assert.equal(divs[4].dy, 0);		
 	}
 };