Include schema validation errors in InvalidMessage stack

Generic error handlers such as FactorioServer.handle() and the event
handler catch in Link only log err.stack, so the ajv errors attached to
an InvalidMessage were lost unless the catch site checked for the class
explicitly. Appending the errors to the stack in the constructor makes
every stack-logging handler show which field failed validation without
special casing each one.

Fixes #986

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

packages/lib/src/errors.ts

@@ -58,6 +58,10 @@ export class InvalidMessage extends Error {
 		public errors?: object | null,
 	) {
 		super(message);
+		// Include the errors in the stack so generic handlers logging it show what failed
+		if (errors) {
+			this.stack += `\n${JSON.stringify(errors, null, "\t")}`;
+		}
 	}
 }
 

packages/lib/src/link/link.ts

@@ -213,7 +213,7 @@ export class Link {
 			let handler = this._eventSnoopers.get((entry as EventEntry).Event)!;
 			let event = message as libData.MessageEvent;
 			handler((entry as EventEntry).eventFromJSON(event.data), event.src, event.dst).catch((err: Error) => {
-				logger.error(`Unexpected error snooping ${event.name}:\n${err.stack}`);
+				logger.error(`Unexpected error snooping ${event.name}:\n${err.stack ?? err.message}`);
 			});
 		}
 
@@ -482,7 +482,7 @@ export class Link {
 		handler(
 			entry.eventFromJSON(message.data), message.src, message.dst
 		).catch((err: Error) => {
-			logger.error(`Unexpected error handling ${message.name}:\n${err.stack}`);
+			logger.error(`Unexpected error handling ${message.name}:\n${err.stack ?? err.message}`);
 		});
 	}
 

test/host/server.js

@@ -311,6 +311,32 @@ describe("host/server", function() {
 			});
 		});
 
+		describe(".handle()", function() {
+			it("should log validation errors from ipc handlers", async function() {
+				let logged = [];
+				let ipcServer = new hostServer.FactorioServer(
+					path.join("test", "file", "factorio"), writePath,
+					{ logger: { error: msg => { logged.push(msg); } } }
+				);
+				class NumberEvent {
+					static type = "event";
+					static src = "instance";
+					static dst = "controller";
+					constructor(value) { this.value = value; }
+					static jsonSchema = { type: "number" };
+					static fromJSON(json) { return new this(json); }
+				}
+				let eventFromJSON = lib.Link.eventFromJSON(NumberEvent, "NumberEvent");
+				ipcServer.handle("bad_event", async () => { eventFromJSON("not a number"); });
+				ipcServer.emit("ipc-bad_event", {});
+				await new Promise(resolve => setImmediate(resolve));
+
+				assert.equal(logged.length, 1);
+				assert(logged[0].startsWith("Error handling ipc event:\nError: Event NumberEvent failed validation\n"));
+				assert(logged[0].includes('"message": "must be number"'));
+			});
+		});
+
 		describe(".stop()", function() {
 			it("should handle server quitting on its own during stop", async function() {
 				server.shutdownTimeoutMs = 20;

test/lib/errors.js

@@ -0,0 +1,24 @@
+"use strict";
+const assert = require("assert").strict;
+
+const lib = require("@clusterio/lib");
+
+describe("lib/errors", function() {
+	describe("class InvalidMessage", function() {
+		it("should include validation errors in the stack", function() {
+			let errors = [{ instancePath: "/value", message: "must be number" }];
+			let err = new lib.InvalidMessage("Request Test failed validation", errors);
+			assert.equal(err.message, "Request Test failed validation");
+			assert.equal(err.errors, errors);
+			assert(err.stack.startsWith("Error: Request Test failed validation\n"));
+			assert(err.stack.endsWith(`\n${JSON.stringify(errors, null, "\t")}`));
+		});
+		it("should leave the stack alone without errors", function() {
+			let err = new lib.InvalidMessage("Unrecognized request Test");
+			assert.equal(err.errors, undefined);
+			assert(!err.stack.includes("\n["));
+			let nullErr = new lib.InvalidMessage("Unrecognized request Test", null);
+			assert.equal(nullErr.errors, null);
+		});
+	});
+});

test/lib/link/link.js

@@ -413,6 +413,25 @@ describe("lib/link/link", function() {
 				testLink.handle(SimpleEvent, async () => { throwSimple("Error"); });
 				testConnector.emit("message", new lib.MessageEvent(1, dst, src, "SimpleEvent"));
 			});
+			it("should log validation errors from event handler", async function() {
+				let logged = [];
+				const originalError = lib.logger.error;
+				lib.logger.error = msg => { logged.push(msg); };
+				try {
+					testLink.handle(SimpleEvent, async () => {
+						testLink.sendEvent(new NumberEvent("not a number"), dst);
+					});
+					testConnector.emit("message", new lib.MessageEvent(1, dst, src, "SimpleEvent"));
+					await new Promise(resolve => setImmediate(resolve));
+				} finally {
+					lib.logger.error = originalError;
+				}
+				assert.equal(logged.length, 1);
+				assert(logged[0].startsWith(
+					"Unexpected error handling SimpleEvent:\nError: Event NumberEvent failed validation\n"
+				));
+				assert(logged[0].includes('"message": "must be number"'));
+			});
 			it("should throw on unknown type", function() {
 				assert.throws(
 					() => testLink.handle({ name: "Bad", type: "bad" }),
@@ -595,6 +614,26 @@ describe("lib/link/link", function() {
 				testLink.snoopEvent(SimpleEvent, async () => { throwSimple("Error"); });
 				testConnector.emit("message", new lib.MessageEvent(1, dst, src, "SimpleEvent"));
 			});
+			it("should log validation errors from snoop handler", async function() {
+				let logged = [];
+				const originalError = lib.logger.error;
+				lib.logger.error = msg => { logged.push(msg); };
+				try {
+					testLink.handle(SimpleEvent, async () => {});
+					testLink.snoopEvent(SimpleEvent, async () => {
+						testLink.sendEvent(new NumberEvent("not a number"), dst);
+					});
+					testConnector.emit("message", new lib.MessageEvent(1, dst, src, "SimpleEvent"));
+					await new Promise(resolve => setImmediate(resolve));
+				} finally {
+					lib.logger.error = originalError;
+				}
+				assert.equal(logged.length, 1);
+				assert(logged[0].startsWith(
+					"Unexpected error snooping SimpleEvent:\nError: Event NumberEvent failed validation\n"
+				));
+				assert(logged[0].includes('"message": "must be number"'));
+			});
 			it("should throw on double registration", function() {
 				testLink.snoopEvent(SimpleEvent);
 				assert.throws(