Enable @typescript eslint/prefer nullish coalescing eslint rule (#1420)

## Description:

Fixes #952 
Enabled @typescript-eslint/prefer-nullish-coalescing rule and worked
through every error, introducing ?? and ??= operators or disabling
errors with inline comments where appropriate, to the best of my
ability.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

g_santos_m

eslint.config.js

@@ -19,6 +19,23 @@ export default [
   pluginJs.configs.recommended,
   ...tseslint.configs.recommended,
   eslintConfigPrettier,
+  {
+    languageOptions: {
+      parserOptions: {
+        projectService: {
+          allowDefaultProject: [
+            "__mocks__/fileMock.js",
+            "eslint.config.js",
+            "jest.config.ts",
+            "postcss.config.js",
+            "tailwind.config.js",
+            "webpack.config.js",
+          ],
+        },
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+  },
   {
     rules: {
       // Disable rules that would fail. The failures should be fixed, and the entries here removed.
@@ -34,6 +51,7 @@ export default [
   {
     rules: {
       // Enable rules
+      "@typescript-eslint/prefer-nullish-coalescing": "error",
       eqeqeq: "error",
     },
   },

src/client/LangSelector.ts

@@ -99,7 +99,7 @@ export class LangSelector extends LitElement {
   private async initializeLanguage() {
     const browserLocale = navigator.language;
     const savedLang = localStorage.getItem("lang");
-    const userLang = this.getClosestSupportedLang(savedLang || browserLocale);
+    const userLang = this.getClosestSupportedLang(savedLang ?? browserLocale);
 
     this.defaultTranslations = this.loadLanguage("en");
     this.translations = this.loadLanguage(userLang);
@@ -110,7 +110,7 @@ export class LangSelector extends LitElement {
   }
 
   private loadLanguage(lang: string): Record<string, string> {
-    const language = this.languageMap[lang] || {};
+    const language = this.languageMap[lang] ?? {};
     const flat = flattenTranslations(language);
     return flat;
   }

src/client/PublicLobby.ts

@@ -110,7 +110,7 @@ export class PublicLobby extends LitElement {
 
     const teamCount =
       lobby.gameConfig.gameMode === GameMode.Team
-        ? lobby.gameConfig.playerTeams || 0
+        ? (lobby.gameConfig.playerTeams ?? 0)
         : null;
 
     const mapImageSrc = this.mapImages.get(lobby.gameID);

src/client/Transport.ts

@@ -245,16 +245,14 @@ export class Transport {
   }
 
   private startPing() {
-    if (this.isLocal || this.pingInterval) return;
-    if (this.pingInterval === null) {
-      this.pingInterval = window.setInterval(() => {
-        if (this.socket !== null && this.socket.readyState === WebSocket.OPEN) {
-          this.sendMsg({
-            type: "ping",
-          } satisfies ClientPingMessage);
-        }
-      }, 5 * 1000);
-    }
+    if (this.isLocal) return;
+    this.pingInterval ??= window.setInterval(() => {
+      if (this.socket !== null && this.socket.readyState === WebSocket.OPEN) {
+        this.sendMsg({
+          type: "ping",
+        } satisfies ClientPingMessage);
+      }
+    }, 5 * 1000);
   }
 
   private stopPing() {

src/client/Utils.ts

@@ -172,7 +172,7 @@ export function getAltKey(): string {
 
 export function getGamesPlayed(): number {
   try {
-    return parseInt(localStorage.getItem("gamesPlayed") || "0", 10) || 0;
+    return parseInt(localStorage.getItem("gamesPlayed") ?? "0", 10) || 0;
   } catch (error) {
     console.warn("Failed to read games played from localStorage:", error);
     return 0;

src/client/graphics/SpriteLoader.ts

@@ -91,9 +91,9 @@ const getSpriteForUnit = (unit: UnitView): ImageBitmap | null => {
   const unitType = unit.type();
   if (unitType === UnitType.Train) {
     const trainType = trainTypeToSpriteType(unit);
-    return spriteMap.get(trainType) || null;
+    return spriteMap.get(trainType) ?? null;
   }
-  return spriteMap.get(unitType) || null;
+  return spriteMap.get(unitType) ?? null;
 };
 
 export const isSpriteReady = (unit: UnitView): boolean => {

src/client/graphics/layers/EventsDisplay.ts

@@ -137,7 +137,7 @@ export class EventsDisplay extends LitElement implements Layer {
   }
 
   private toggleEventFilter(filterName: MessageCategory) {
-    const currentState = this.eventsFilters.get(filterName) || false;
+    const currentState = this.eventsFilters.get(filterName) ?? false;
     this.eventsFilters.set(filterName, !currentState);
     this.requestUpdate();
   }

src/client/graphics/layers/RadialMenu.ts

@@ -298,14 +298,14 @@ export class RadialMenu implements Layer {
         const disabled = this.params === null || d.data.disabled(this.params);
         const color = disabled
           ? this.config.disabledColor
-          : d.data.color || "#333333";
+          : (d.data.color ?? "#333333");
         const opacity = disabled ? 0.5 : 0.7;
 
         if (d.data.id === this.selectedItemId && this.currentLevel > level) {
           return color;
         }
 
-        return d3.color(color)?.copy({ opacity: opacity })?.toString() || color;
+        return d3.color(color)?.copy({ opacity: opacity })?.toString() ?? color;
       })
       .attr("stroke", "#ffffff")
       .attr("stroke-width", "2")
@@ -341,7 +341,7 @@ export class RadialMenu implements Layer {
         const color =
           this.params === null || d.data.disabled(this.params)
             ? this.config.disabledColor
-            : d.data.color || "#333333";
+            : (d.data.color ?? "#333333");
         path.attr("fill", color);
       }
     });
@@ -405,11 +405,11 @@ export class RadialMenu implements Layer {
       path.attr("stroke-width", "2");
       const color = disabled
         ? this.config.disabledColor
-        : d.data.color || "#333333";
+        : (d.data.color ?? "#333333");
       const opacity = disabled ? 0.5 : 0.7;
       path.attr(
         "fill",
-        d3.color(color)?.copy({ opacity: opacity })?.toString() || color,
+        d3.color(color)?.copy({ opacity: opacity })?.toString() ?? color,
       );
     };
 
@@ -625,7 +625,7 @@ export class RadialMenu implements Layer {
       this.selectedItemId = null;
     }
 
-    this.currentMenuItems = previousItems || [];
+    this.currentMenuItems = previousItems ?? [];
 
     if (this.currentLevel === 0) {
       this.updateCenterButtonState("default");
@@ -645,11 +645,11 @@ export class RadialMenu implements Layer {
           const disabled = this.params === null || item.disabled(this.params);
           const color = disabled
             ? this.config.disabledColor
-            : item.color || "#333333";
+            : (item.color ?? "#333333");
           const opacity = disabled ? 0.5 : 0.7;
           selectedPath.attr(
             "fill",
-            d3.color(color)?.copy({ opacity: opacity })?.toString() || color,
+            d3.color(color)?.copy({ opacity: opacity })?.toString() ?? color,
           );
         }
       }

src/client/graphics/layers/RadialMenuElements.ts

@@ -352,9 +352,9 @@ export const buildMenuElement: MenuElement = {
           : undefined,
         icon: item.icon,
         tooltipItems: [
-          { text: translateText(item.key || ""), className: "title" },
+          { text: translateText(item.key ?? ""), className: "title" },
           {
-            text: translateText(item.description || ""),
+            text: translateText(item.description ?? ""),
             className: "description",
           },
           {
@@ -401,7 +401,7 @@ export const boatMenuElement: MenuElement = {
 
     params.playerActionHandler.handleBoatAttack(
       params.myPlayer,
-      params.selected?.id() || null,
+      params.selected?.id() ?? null,
       params.tile,
       spawn !== false ? spawn : null,
     );

src/client/graphics/layers/TeamStats.ts

@@ -52,7 +52,7 @@ export class TeamStats extends LitElement implements Layer {
     for (const player of players) {
       const team = player.team();
       if (team === null) continue;
-      if (!grouped[team]) grouped[team] = [];
+      grouped[team] ??= [];
       grouped[team].push(player);
     }
 

src/client/graphics/layers/UILayer.ts

@@ -317,10 +317,16 @@ export class UILayer implements Layer {
         if (constructionType === undefined) {
           return 1;
         }
+        const constDuration =
+          this.game.unitInfo(constructionType).constructionDuration;
+        if (constDuration === undefined) {
+          throw new Error("unit does not have constructionTime");
+        }
         return (
           (this.game.ticks() - unit.createdAt()) /
-          (this.game.unitInfo(constructionType).constructionDuration || 1)
+          (constDuration === 0 ? 1 : constDuration)
         );
+
       case UnitType.MissileSilo:
       case UnitType.SAMLauncher:
         return unit.missileReadinesss();

src/client/jwt.ts

@@ -104,9 +104,8 @@ export type IsLoggedInResponse =
   | false;
 let __isLoggedIn: IsLoggedInResponse | undefined = undefined;
 export function isLoggedIn(): IsLoggedInResponse {
-  if (__isLoggedIn === undefined) {
-    __isLoggedIn = _isLoggedIn();
-  }
+  __isLoggedIn ??= _isLoggedIn();
+
   return __isLoggedIn;
 }
 function _isLoggedIn(): IsLoggedInResponse {

src/core/Util.ts

@@ -119,7 +119,7 @@ export function getMode(list: Set<number>): number {
   // Count occurrences
   const counts = new Map<number, number>();
   for (const item of list) {
-    counts.set(item, (counts.get(item) || 0) + 1);
+    counts.set(item, (counts.get(item) ?? 0) + 1);
   }
 
   // Find the item with the highest count

src/core/execution/AttackExecution.ts

@@ -97,11 +97,9 @@ export class AttackExecution implements Execution {
       }
     }
 
-    if (this.startTroops === null) {
-      this.startTroops = this.mg
-        .config()
-        .attackAmount(this._owner, this.target);
-    }
+    this.startTroops ??= this.mg
+      .config()
+      .attackAmount(this._owner, this.target);
     if (this.removeTroops) {
       this.startTroops = Math.min(this._owner.troops(), this.startTroops);
       this._owner.removeTroops(this.startTroops);

src/core/execution/DonateGoldExecution.ts

@@ -19,9 +19,7 @@ export class DonateGoldExecution implements Execution {
     }
 
     this.recipient = mg.player(this.recipientID);
-    if (this.gold === null) {
-      this.gold = this.sender.gold() / 3n;
-    }
+    this.gold ??= this.sender.gold() / 3n;
   }
 
   tick(ticks: number): void {

src/core/execution/DonateTroopExecution.ts

@@ -19,9 +19,7 @@ export class DonateTroopsExecution implements Execution {
     }
 
     this.recipient = mg.player(this.recipientID);
-    if (this.troops === null) {
-      this.troops = mg.config().defaultDonationAmount(this.sender);
-    }
+    this.troops ??= mg.config().defaultDonationAmount(this.sender);
     const maxDonation =
       mg.config().maxPopulation(this.recipient) - this.recipient.population();
     this.troops = Math.min(this.troops, maxDonation);

src/core/execution/SAMLauncherExecution.ts

@@ -109,9 +109,7 @@ export class SAMLauncherExecution implements Execution {
       this.player = this.sam.owner();
     }
 
-    if (this.pseudoRandom === undefined) {
-      this.pseudoRandom = new PseudoRandom(this.sam.id());
-    }
+    this.pseudoRandom ??= new PseudoRandom(this.sam.id());
 
     const mirvWarheadTargets = this.mg.nearbyUnits(
       this.sam.tile(),

src/core/execution/SAMMissileExecution.ts

@@ -31,13 +31,11 @@ export class SAMMissileExecution implements Execution {
   }
 
   tick(ticks: number): void {
-    if (this.SAMMissile === undefined) {
-      this.SAMMissile = this._owner.buildUnit(
-        UnitType.SAMMissile,
-        this.spawn,
-        {},
-      );
-    }
+    this.SAMMissile ??= this._owner.buildUnit(
+      UnitType.SAMMissile,
+      this.spawn,
+      {},
+    );
     if (!this.SAMMissile.isActive()) {
       this.active = false;
       return;

src/core/execution/ShellExecution.ts

@@ -23,9 +23,7 @@ export class ShellExecution implements Execution {
   }
 
   tick(ticks: number): void {
-    if (this.shell === undefined) {
-      this.shell = this._owner.buildUnit(UnitType.Shell, this.spawn, {});
-    }
+    this.shell ??= this._owner.buildUnit(UnitType.Shell, this.spawn, {});
     if (!this.shell.isActive()) {
       this.active = false;
       return;

src/core/execution/TransportShipExecution.ts

@@ -89,11 +89,9 @@ export class TransportShipExecution implements Execution {
       this.target = mg.player(this.targetID);
     }
 
-    if (this.troops === null) {
-      this.troops = this.mg
-        .config()
-        .boatAttackAmount(this.attacker, this.target);
-    }
+    this.troops ??= this.mg
+      .config()
+      .boatAttackAmount(this.attacker, this.target);
 
     this.troops = Math.min(this.troops, this.attacker.troops());
 

src/core/game/GameView.ts

@@ -507,9 +507,7 @@ export class GameView implements GameMap {
   }
 
   myPlayer(): PlayerView | null {
-    if (this._myPlayer === null) {
-      this._myPlayer = this.playerByClientID(this._myClientID);
-    }
+    this._myPlayer ??= this.playerByClientID(this._myClientID);
     return this._myPlayer;
   }
 

src/core/game/StatsImpl.ts

@@ -66,7 +66,7 @@ export class StatsImpl implements Stats {
   private _addAttack(player: Player, index: number, value: BigIntLike) {
     const p = this._makePlayerStats(player);
     if (p === undefined) return;
-    if (p.attacks === undefined) p.attacks = [0n];
+    p.attacks ??= [0n];
     while (p.attacks.length <= index) p.attacks.push(0n);
     p.attacks[index] += _bigint(value);
   }
@@ -89,8 +89,8 @@ export class StatsImpl implements Stats {
   ) {
     const p = this._makePlayerStats(player);
     if (p === undefined) return;
-    if (p.boats === undefined) p.boats = { [type]: [0n] };
-    if (p.boats[type] === undefined) p.boats[type] = [0n];
+    p.boats ??= { [type]: [0n] };
+    p.boats[type] ??= [0n];
     while (p.boats[type].length <= index) p.boats[type].push(0n);
     p.boats[type][index] += _bigint(value);
   }
@@ -104,8 +104,8 @@ export class StatsImpl implements Stats {
     const type = unitTypeToBombUnit[nukeType];
     const p = this._makePlayerStats(player);
     if (p === undefined) return;
-    if (p.bombs === undefined) p.bombs = { [type]: [0n] };
-    if (p.bombs[type] === undefined) p.bombs[type] = [0n];
+    p.bombs ??= { [type]: [0n] };
+    p.bombs[type] ??= [0n];
     while (p.bombs[type].length <= index) p.bombs[type].push(0n);
     p.bombs[type][index] += _bigint(value);
   }
@@ -113,7 +113,7 @@ export class StatsImpl implements Stats {
   private _addGold(player: Player, index: number, value: BigIntLike) {
     const p = this._makePlayerStats(player);
     if (p === undefined) return;
-    if (p.gold === undefined) p.gold = [0n];
+    p.gold ??= [0n];
     while (p.gold.length <= index) p.gold.push(0n);
     p.gold[index] += _bigint(value);
   }
@@ -127,8 +127,8 @@ export class StatsImpl implements Stats {
     const type = unitTypeToOtherUnit[otherUnitType];
     const p = this._makePlayerStats(player);
     if (p === undefined) return;
-    if (p.units === undefined) p.units = { [type]: [0n] };
-    if (p.units[type] === undefined) p.units[type] = [0n];
+    p.units ??= { [type]: [0n] };
+    p.units[type] ??= [0n];
     while (p.units[type].length <= index) p.units[type].push(0n);
     p.units[type][index] += _bigint(value);
   }

src/core/game/TerrainMapFileLoader.ts

@@ -26,9 +26,7 @@ class GameMapLoader {
   private createLazyLoader<T>(importFn: () => Promise<T>): () => Promise<T> {
     let cache: Promise<T> | null = null;
     return () => {
-      if (!cache) {
-        cache = importFn();
-      }
+      cache ??= importFn();
       return cache;
     };
   }

src/server/Archive.ts

@@ -37,7 +37,7 @@ export async function archive(gameRecord: GameRecord) {
     }
   } catch (error) {
     log.error(`${gameRecord.info.gameID}: Final archive error: ${error}`, {
-      message: error?.message || error,
+      message: error?.message ?? error,
       stack: error?.stack,
       name: error?.name,
       ...(error && typeof error === "object" ? error : {}),
@@ -70,7 +70,7 @@ async function archiveAnalyticsToR2(gameRecord: GameRecord) {
     log.info(`${info.gameID}: successfully wrote game analytics to R2`);
   } catch (error) {
     log.error(`${info.gameID}: Error writing game analytics to R2: ${error}`, {
-      message: error?.message || error,
+      message: error?.message ?? error,
       stack: error?.stack,
       name: error?.name,
       ...(error && typeof error === "object" ? error : {}),
@@ -119,7 +119,7 @@ export async function readGameRecord(
   } catch (error) {
     // Log the error for monitoring purposes
     log.error(`${gameId}: Error reading game record from R2: ${error}`, {
-      message: error?.message || error,
+      message: error?.message ?? error,
       stack: error?.stack,
       name: error?.name,
       ...(error && typeof error === "object" ? error : {}),
@@ -142,7 +142,7 @@ export async function gameRecordExists(gameId: GameID): Promise<boolean> {
       return false;
     }
     log.error(`${gameId}: Error checking archive existence: ${error}`, {
-      message: error?.message || error,
+      message: error?.message ?? error,
       stack: error?.stack,
       name: error?.name,
       ...(error && typeof error === "object" ? error : {}),

src/server/Cloudflare.ts

@@ -162,7 +162,9 @@ export class Cloudflare {
     );
 
     const credentials = {
+      // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
       AccountTag: tokenData.a || this.accountId,
+      // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
       TunnelID: tokenData.t || tunnelId,
       TunnelName: tunnelName,
       TunnelSecret: tokenData.s,

src/server/GameServer.ts

@@ -694,7 +694,7 @@ export class GameServer {
     for (const client of this.activeClients) {
       if (client.hashes.has(turnNumber)) {
         const clientHash = client.hashes.get(turnNumber)!;
-        counts.set(clientHash, (counts.get(clientHash) || 0) + 1);
+        counts.set(clientHash, (counts.get(clientHash) ?? 0) + 1);
       }
     }
 

src/server/Master.ts

@@ -146,8 +146,9 @@ app.get(
   "/api/env",
   gatekeeper.httpHandler(LimiterType.Get, async (req, res) => {
     const envConfig = {
-      game_env: process.env.GAME_ENV || "prod",
+      game_env: process.env.GAME_ENV,
     };
+    if (!envConfig.game_env) return res.sendStatus(500);
     res.json(envConfig);
   }),
 );

src/server/Worker.ts

@@ -29,7 +29,7 @@ import { initWorkerMetrics } from "./WorkerMetrics";
 
 const config = getServerConfigFromServer();
 
-const workerId = parseInt(process.env.WORKER_ID || "0");
+const workerId = parseInt(process.env.WORKER_ID ?? "0");
 const log = logger.child({ comp: `w_${workerId}` });
 
 // Worker setup
@@ -94,6 +94,7 @@ export function startWorker() {
         log.warn(`cannot create game, id not found`);
         return res.status(400).json({ error: "Game ID is required" });
       }
+      // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
       const clientIP = req.ip || req.socket.remoteAddress || "unknown";
       const result = CreateGameInputSchema.safeParse(req.body);
       if (!result.success) {
@@ -140,6 +141,7 @@ export function startWorker() {
         return;
       }
       if (game.isPublic()) {
+        // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
         const clientIP = req.ip || req.socket.remoteAddress || "unknown";
         log.info(
           `cannot start public game ${game.id}, game is public, ip: ${ipAnonymize(clientIP)}`,
@@ -171,6 +173,7 @@ export function startWorker() {
         return res.status(400).json({ error: "Game not found" });
       }
       if (game.isPublic()) {
+        // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
         const clientIP = req.ip || req.socket.remoteAddress || "unknown";
         log.warn(
           `cannot update public game ${game.id}, ip: ${ipAnonymize(clientIP)}`,
@@ -296,7 +299,8 @@ export function startWorker() {
         const forwarded = req.headers["x-forwarded-for"];
         const ip = Array.isArray(forwarded)
           ? forwarded[0]
-          : forwarded || req.socket.remoteAddress || "unknown";
+          : // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
+            forwarded || req.socket.remoteAddress || "unknown";
 
         try {
           // Parse and handle client messages