Throw on a missing file when loadJsonObject is asked to

Controller.loadJsonObject(path, true) returned {} for a missing file, so
loadPlugins' catch never ran and a plugin whose web build was expected but
missing was not reported (the second half of #1046; #1047 fixed the path).
With throwOnMissing set, every error now throws; without it only a missing
file is ignored, so a malformed JSON file throws again as before #1047.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BGUULoiHNbAegwMK4PSjHJ

CHANGELOG.md

@@ -47,6 +47,7 @@ Many thanks to the following for contributing to this release:
 
 ### Fixes
 
+- A plugin whose web build is expected but missing is reported again: `Controller.loadJsonObject(path, true)` throws on a missing file instead of returning `{}`, and a malformed JSON file always throws. [#1046](<https://github.com/clusterio/clusterio/issues/1046>)
 - Allow player online autosave slots to be disabled while autosaves are enabled. [#966](<https://github.com/clusterio/clusterio/issues/966>)
 - Silenced two Ant Design console warnings in the Web UI: the deprecated Modal `destroyOnClose` prop, and a duplicate-value warning from the instance version selector. [#940](<https://github.com/clusterio/clusterio/pull/940>)
 - Surface the mod portal's own error when downloading mods for an unsupported Factorio version. [#941](<https://github.com/clusterio/clusterio/pull/941>)

packages/controller/src/Controller.ts

@@ -842,7 +842,7 @@ export default class Controller {
 		try {
 			manifest = JSON.parse(await fs.readFile(filePath, { encoding: "utf8" }));
 		} catch (err: any) {
-			if (throwOnMissing && err.code !== "ENOENT") {
+			if (throwOnMissing || err.code !== "ENOENT") {
 				throw err;
 			}
 		}

test/controller/Controller.js

@@ -1,3 +1,5 @@
+import fs from "node:fs/promises";
+import os from "node:os";
 import path from "node:path";
 import assert from "node:assert/strict";
 import { Controller, HostRecord, InstanceRecord, UserRecord } from "@clusterio/controller";
@@ -55,6 +57,35 @@ describe("controller/src/Controller", function() {
 				assert(list.check(ip), `${ip} missing from list`);
 			}
 		}
+		describe(".loadJsonObject()", function() {
+			let dir;
+			before(async function() {
+				dir = await fs.mkdtemp(path.join(os.tmpdir(), "clusterio-load-json-"));
+				await fs.writeFile(path.join(dir, "valid.json"), JSON.stringify({ "main.js": "main.123.js" }));
+				await fs.writeFile(path.join(dir, "invalid.json"), "{ not json");
+			});
+			after(async function() {
+				await fs.rm(dir, { recursive: true, force: true });
+			});
+			it("should parse an existing file", async function() {
+				assert.deepEqual(
+					await Controller.loadJsonObject(path.join(dir, "valid.json")),
+					{ "main.js": "main.123.js" },
+				);
+			});
+			it("should return an empty object for a missing file by default", async function() {
+				assert.deepEqual(await Controller.loadJsonObject(path.join(dir, "missing.json")), {});
+			});
+			it("should throw for a missing file when throwOnMissing is set", async function() {
+				await assert.rejects(
+					Controller.loadJsonObject(path.join(dir, "missing.json"), true),
+					{ code: "ENOENT" },
+				);
+			});
+			it("should throw for invalid JSON", async function() {
+				await assert.rejects(Controller.loadJsonObject(path.join(dir, "invalid.json")), SyntaxError);
+			});
+		});
 		describe(".serveWeb()", function() {
 			let server, port;
 			before(async function() {