various stability improvements

sapper-dev-client.js

@@ -0,0 +1,38 @@
+let source;
+
+function check() {
+	if (module.hot.status() === 'idle') {
+		module.hot.check(true).then(modules => {
+			console.log(`[SAPPER] applied HMR update`);
+		});
+	}
+}
+
+export function connect(port) {
+	if (source || !window.EventSource) return;
+
+	source = new EventSource(`http://localhost:${port}/__sapper__`);
+
+	window.source = source;
+
+	source.onopen = function(event) {
+		console.log(`[SAPPER] dev client connected`);
+	};
+
+	source.onerror = function(error) {
+		console.error(error);
+	};
+
+	source.onmessage = function(event) {
+		const data = JSON.parse(event.data);
+		if (!data) return; // just a heartbeat
+
+		if (data.action === 'reload') {
+			window.location.reload();
+		}
+
+		if (data.status === 'completed') {
+			check();
+		}
+	};
+}