implement preload

src/generators/Generator.ts

@@ -598,6 +598,10 @@ export default class Generator {
 					addDeclaration('ondestroy', templateProperties.ondestroy.value);
 				}
 
+				if (templateProperties.preload) {
+					addDeclaration('preload', templateProperties.preload.value);
+				}
+
 				if (templateProperties.props) {
 					this.props = templateProperties.props.value.elements.map((element: Node) => element.value);
 				}

src/generators/dom/index.ts

@@ -358,6 +358,8 @@ export default function dom(
 		` : (!sharedPath && `${name}.prototype._recompute = @noop;`)}
 
 		${templateProperties.setup && `%setup(${name});`}
+
+		${templateProperties.preload && `${name}.preload = %preload;`}
 	`);
 
 	const usedHelpers = new Set();

src/generators/server-side-rendering/index.ts

@@ -162,6 +162,8 @@ export default function ssr(
 			};
 		};
 
+		${templateProperties.preload && `${name}.preload = %preload;`}
+
 		${
 			// TODO this is a bit hacky
 			/__escape/.test(generator.renderCode) && deindent`

src/validate/js/propValidators/index.ts

@@ -9,6 +9,7 @@ import methods from './methods';
 import components from './components';
 import events from './events';
 import namespace from './namespace';
+import preload from './preload';
 import props from './props';
 import tag from './tag';
 import transitions from './transitions';
@@ -26,6 +27,7 @@ export default {
 	components,
 	events,
 	namespace,
+	preload,
 	props,
 	tag,
 	transitions,

src/validate/js/propValidators/preload.ts

@@ -0,0 +1,13 @@
+import { Validator } from '../../';
+import { Node } from '../../../interfaces';
+
+const validTypes = new Set([
+	'FunctionExpression',
+	'ArrowFunctionExpression',
+	'Identifier',
+	'MemberExpression'
+]);
+
+export default function preload(validator: Validator, prop: Node) {
+	// not sure there's anything we need to check here...
+}

test/js/samples/ssr-no-oncreate-etc/expected-bundle.js

@@ -1,3 +1,7 @@
+function preload(input) {
+	return output;
+}
+
 var SvelteComponent = {};
 
 SvelteComponent.data = function() {
@@ -20,4 +24,6 @@ SvelteComponent.renderCss = function() {
 	};
 };
 
+SvelteComponent.preload = preload;
+
 module.exports = SvelteComponent;

test/js/samples/ssr-no-oncreate-etc/expected.js

@@ -1,5 +1,9 @@
 "use strict";
 
+function preload(input) {
+	return output;
+};
+
 var SvelteComponent = {};;
 
 SvelteComponent.data = function() {
@@ -22,4 +26,6 @@ SvelteComponent.renderCss = function() {
 	};
 };
 
+SvelteComponent.preload = preload;
+
 module.exports = SvelteComponent;

test/js/samples/ssr-no-oncreate-etc/input.html

@@ -18,6 +18,10 @@
 			swipe(node, callback) {
 				// TODO implement
 			}
+		},
+
+		preload(input) {
+			return output;
 		}
 	};
 </script>

test/runtime/samples/preload/_config.js

@@ -0,0 +1,6 @@
+export default {
+	test(assert, component) {
+		const Component = component.constructor;
+		assert.deepEqual(Component.preload({ foo: 1 }), { bar: 2 });
+	}
+};

test/runtime/samples/preload/main.html

@@ -0,0 +1,9 @@
+<script>
+	export default {
+		preload({ foo }) {
+			return {
+				bar: foo * 2
+			};
+		}
+	};
+</script>