bind:value as Date support for <input type=date> tags

* (breaking change) changes the current `bind:value` behavior that returns a date string of `yyyy-mm-dd` so that it will return a `Date` value instead.

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

@@ -325,6 +325,10 @@ function get_value_from_dom(
 		return `@to_number(this.${name})`;
 	}
 
+	if (type === 'date') {
+		return `@value_as_date(this.${name})`;
+	}
+
 	if ((name === 'buffered' || name === 'seekable' || name === 'played')) {
 		return `@time_ranges_to_array(this.${name})`;
 	}

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

@@ -64,6 +64,11 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 		node.attributes.some((attribute) => attribute.name === 'contenteditable')
 	);
 
+	const is_date_input = (
+		node.name === 'input' &&
+		node.attributes.some((attribute) => attribute.name === 'type' && attribute.get_static_value() === 'date')
+	);
+
 	const slot = node.get_static_attribute_value('slot');
 	const component = node.find_nearest(/InlineComponent/);
 	if (slot && component) {
@@ -162,6 +167,9 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 		} else if (binding.name === 'value' && node.name === 'textarea') {
 			const snippet = snip(expression);
 			node_contents = '${(' + snippet + ') || ""}';
+		} else if (binding.name === 'value' && is_date_input) {
+			const snippet = snip(expression);
+			opening_tag += '${@add_attribute("' + name + '", @date_as_value(' + snippet + '), 1)}';
 		} else {
 			const snippet = snip(expression);
 			opening_tag += '${@add_attribute("' + name + '", ' + snippet + ', 1)}';

src/runtime/internal/dom.ts

@@ -125,6 +125,22 @@ export function to_number(value) {
 	return value === '' ? undefined : +value;
 }
 
+export function value_as_date(value) {
+	const valueAsDate = new Date(value);
+	return isNaN(valueAsDate.getTime()) ? undefined : valueAsDate;
+}
+
+export function date_as_value(date) {
+	const validDate = Object.prototype.toString.call(date) === '[object Date]' && !isNaN(date.getTime());
+	if (!validDate) {
+		return '';
+	}
+	const yyyy = date.getUTCFullYear();
+	const mm = date.getUTCMonth() + 1 < 10 ? `0${date.getUTCMonth() + 1}` : date.getUTCMonth() + 1;
+	const dd = date.getUTCDate() < 10 ? `0${date.getUTCDate()}` : date.getUTCDate();
+	return `${yyyy}-${mm}-${dd}`;
+}
+
 export function time_ranges_to_array(ranges) {
 	const array = [];
 	for (let i = 0; i < ranges.length; i += 1) {
@@ -170,7 +186,9 @@ export function set_data(text, data) {
 }
 
 export function set_input_value(input, value) {
-	if (value != null || input.value) {
+	if (Object.prototype.toString.call(value) === '[object Date]') {
+		input.value = date_as_value(value);
+	} else if (value != null || input.value) {
 		input.value = value;
 	}
 }

test/runtime/samples/binding-input-date/_config.js

@@ -0,0 +1,55 @@
+const SEP_03_2019_INPUT_VALUE = '2019-09-03';
+const SEP_03_2019_DATE_VALUE = new Date(SEP_03_2019_INPUT_VALUE);
+
+const OCT_07_2019_INPUT_VALUE = '2019-10-07';
+const OCT_07_2019_DATE_VALUE = new Date(OCT_07_2019_INPUT_VALUE);
+
+export default {
+	props: {
+		date: SEP_03_2019_DATE_VALUE
+	},
+
+	html: `
+		<input type=date>
+		<p>[object Date] ${SEP_03_2019_DATE_VALUE}</p>
+	`,
+
+	ssrHtml: `
+		<input type=date value='${SEP_03_2019_INPUT_VALUE}'>
+		<p>[object Date] ${SEP_03_2019_DATE_VALUE}</p>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const input = target.querySelector('input');
+		assert.equal(input.value, SEP_03_2019_INPUT_VALUE);
+		assert.equal(component.date.toString(), SEP_03_2019_DATE_VALUE.toString());
+
+		const event = new window.Event('input');
+
+		input.value = OCT_07_2019_INPUT_VALUE;
+		await input.dispatchEvent(event);
+
+		assert.equal(component.date.toString(), OCT_07_2019_DATE_VALUE.toString());
+		assert.htmlEqual(target.innerHTML, `
+			<input type='date'>
+			<p>[object Date] ${OCT_07_2019_DATE_VALUE}</p>
+		`);
+
+		component.date = SEP_03_2019_DATE_VALUE;
+		assert.equal(input.value, SEP_03_2019_INPUT_VALUE);
+		assert.htmlEqual(target.innerHTML, `
+			<input type='date'>
+			<p>[object Date] ${SEP_03_2019_DATE_VALUE}</p>
+		`);
+
+		// empty string should be treated as undefined
+		input.value = '';
+		await input.dispatchEvent(event);
+
+		assert.equal(component.date, undefined);
+		assert.htmlEqual(target.innerHTML, `
+			<input type='date'>
+			<p>[object Undefined] undefined</p>
+		`);
+	},
+};

test/runtime/samples/binding-input-date/main.svelte

@@ -0,0 +1,6 @@
+<script>
+	export let date;
+</script>
+
+<input type='date' bind:value={date}>
+<p>{Object.prototype.toString.call(date)} {date}</p>