fix: prevent restart downgrades (#951)

Co-authored-by: Loi Nguyen <1948922+lntutor@users.noreply.github.com>

test/controller/ControlConnection.test.js

@@ -0,0 +1,42 @@
+"use strict";
+const assert = require("assert").strict;
+const { ControlConnection } = require("@clusterio/controller");
+
+describe("controller/src/ControlConnection", function() {
+	describe(".handleControllerRestartRequest()", function() {
+		let mockController;
+
+		beforeEach(function() {
+			mockController = {
+				canRestart: true,
+				shouldRestart: false,
+				stopped: false,
+				async checkRestartDowngrade() { return null; },
+				stop() { this.stopped = true; },
+			};
+		});
+
+		async function restart() {
+			await ControlConnection.prototype.handleControllerRestartRequest.call({
+				_controller: mockController,
+			});
+		}
+
+		it("restarts when the installed version is not older", async function() {
+			await restart();
+			assert.equal(mockController.shouldRestart, true);
+			assert.equal(mockController.stopped, true);
+		});
+
+		it("rejects a downgrade without stopping the controller", async function() {
+			mockController.checkRestartDowngrade = async () => ({
+				installedVersion: "1.0.0",
+				runningVersion: "2.0.0",
+			});
+
+			await assert.rejects(restart, /Stop the controller before starting the older version manually/);
+			assert.equal(mockController.shouldRestart, false);
+			assert.equal(mockController.stopped, false);
+		});
+	});
+});