Log errors from instance config change handlers

The fieldChanged handler in the Instance constructor ran
updateFactorioSettings and updateFactorioWhitelist with only a finally
attached. A rejection from either went unhandled, and the host exits on
unhandled rejections, taking every instance on it down.

Two ways to hit it against a real host:

- Start an instance and immediately toggle factorio.enable_whitelist.
  updateFactorioWhitelist calls sendRcon while the server state is still
  "new" and it throws "Expected state running,stopping but state is new".
- Set factorio.settings tags to [1] on a running instance. applyAsConfig
  called tag.replace outside its try block and threw
  "tag.replace is not a function".

Catch and log both on the instance logger before invoking the hook, and
convert tags with String() so non-string entries no longer throw.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/host/src/Instance.ts

@@ -61,7 +61,7 @@ function applyAsConfig(name: string) {
 			// Replace spaces with non-break spaces and delimit by spaces.
 			// This does change the defined tags, but there doesn't seem to
 			// be a way to include a space into a tag from the console.
-			value = value.map(tag => tag.replace(/ /g, "\u00a0")).join(" ");
+			value = value.map(tag => String(tag).replace(/ /g, "\u00a0")).join(" ");
 		}
 		try {
 			await instance.sendRcon(`/config set ${name} ${value}`);
@@ -199,9 +199,13 @@ export default class Instance extends lib.Link {
 			if (field === "factorio.shutdown_timeout") {
 				this.server.shutdownTimeoutMs = curr as number * 1000;
 			} else if (field === "factorio.settings") {
-				this.updateFactorioSettings(curr as any, prev as any).finally(hook);
+				this.updateFactorioSettings(curr as any, prev as any).catch(err => {
+					this.logger.error(`Error updating server settings:\n${err.stack}`);
+				}).finally(hook);
 			} else if (field === "factorio.enable_whitelist") {
-				this.updateFactorioWhitelist(curr as any).finally(hook);
+				this.updateFactorioWhitelist(curr as any).catch(err => {
+					this.logger.error(`Error updating whitelist:\n${err.stack}`);
+				}).finally(hook);
 			} else {
 				if (field === "factorio.max_concurrent_commands") {
 					this.server.maxConcurrentCommands = curr as number;

test/host/Instance.js

@@ -4,7 +4,7 @@ import path from "node:path";
 import * as lib from "@clusterio/lib";
 import { PlayerStats, wait } from "@clusterio/lib";
 import Instance from "@clusterio/host/dist/node/src/Instance.js";
-import { MockConnector, MockServer } from "../mock.js";
+import { MockConnector, MockLogger, MockServer } from "../mock.js";
 
 const addr = lib.Address.fromShorthand;
 
@@ -38,6 +38,56 @@ describe("class Instance", function() {
 		});
 	});
 
+	describe("config fieldChanged", function() {
+		let errors;
+		let rejections;
+		let hookInvoked;
+		function onRejection(err) { rejections.push(err); }
+		beforeEach(function() {
+			errors = [];
+			rejections = [];
+			instance.logger = new MockLogger();
+			instance.logger.error = message => errors.push(message);
+			instance.server.exampleSettings = async () => ({});
+			hookInvoked = new Promise(resolve => {
+				instance.hooks.instanceConfigFieldChanged.attach("test", field => resolve(field));
+			});
+			process.on("unhandledRejection", onRejection);
+		});
+		afterEach(function() {
+			process.off("unhandledRejection", onRejection);
+		});
+
+		it("should log whitelist update errors and invoke the hook", async function() {
+			instance.server.sendRcon = async () => { throw new Error("Expected state running,stopping"); };
+			instance.config.set("factorio.enable_whitelist", true);
+			assert.equal(await hookInvoked, "factorio.enable_whitelist");
+			await wait(10);
+			assert.deepEqual(rejections, []);
+			assert.equal(errors.length, 1);
+			assert.match(errors[0], /^Error updating whitelist:\nError: Expected state running,stopping/);
+		});
+
+		it("should log server settings update errors and invoke the hook", async function() {
+			instance.server.exampleSettings = async () => { throw new Error("no example settings"); };
+			instance.config.set("factorio.settings", { name: "bar" });
+			assert.equal(await hookInvoked, "factorio.settings");
+			await wait(10);
+			assert.deepEqual(rejections, []);
+			assert.equal(errors.length, 1);
+			assert.match(errors[0], /^Error updating server settings:\nError: no example settings/);
+		});
+
+		it("should apply tags with non-string elements", async function() {
+			instance.config.set("factorio.settings", { tags: [1, "a b"] });
+			await hookInvoked;
+			await wait(10);
+			assert.deepEqual(rejections, []);
+			assert.deepEqual(errors, []);
+			assert.deepEqual(instance.server.rconCommands, ["/config set tags 1 a b"]);
+		});
+	});
+
 	describe(".checkModPackVersion()", function() {
 		function modPack(factorioVersion) {
 			return lib.ModPack.fromJSON({ name: "pack", factorio_version: factorioVersion });