chore: migrate from ESLint to Biome for linting

biome.json

@@ -0,0 +1,142 @@
+{
+	"$schema": "https://biomejs.dev/schemas/2.5.0/schema.json",
+	"vcs": { "enabled": true, "clientKind": "git", "useIgnoreFile": true },
+	"files": {
+		"ignoreUnknown": false,
+		"includes": ["**", "!build/**", "!.agent/**", "!src/evolution-types/**"]
+	},
+	"formatter": { "enabled": false },
+	"assist": { "enabled": false },
+	"linter": {
+		"enabled": true,
+		"rules": {
+			"recommended": false,
+			"complexity": {
+				"noBannedTypes": "error",
+				"noUselessThisAlias": "error",
+				"noUselessTypeConstraint": "error"
+			},
+			"correctness": { "noUnusedVariables": "error" },
+			"style": {
+				"noCommonJs": "error",
+				"noNamespace": "error",
+				"useArrayLiterals": "error",
+				"useAsConstAssertion": "error"
+			},
+			"suspicious": {
+				"noDuplicateEnumValues": "error",
+				"noExplicitAny": "error",
+				"noExtraNonNullAssertion": "error",
+				"noMisleadingInstantiator": "error",
+				"noNonNullAssertedOptionalChain": "error",
+				"noTsIgnore": "error",
+				"noUnsafeDeclarationMerging": "error",
+				"useNamespaceKeyword": "error"
+			}
+		}
+	},
+	"javascript": { "globals": [] },
+	"overrides": [
+		{
+			"includes": ["**/*.{js,mjs,cjs,ts,mts,cts}", "!build/**"],
+			"linter": {
+				"rules": {
+					"complexity": {
+						"noAdjacentSpacesInRegex": "error",
+						"noExtraBooleanCast": "error",
+						"noUselessCatch": "error",
+						"noUselessEscapeInRegex": "error"
+					},
+					"correctness": {
+						"noConstAssign": "error",
+						"noConstantCondition": "error",
+						"noEmptyCharacterClassInRegex": "error",
+						"noEmptyPattern": "error",
+						"noGlobalObjectCalls": "error",
+						"noInvalidBuiltinInstantiation": "error",
+						"noInvalidConstructorSuper": "error",
+						"noNonoctalDecimalEscape": "error",
+						"noPrecisionLoss": "error",
+						"noSelfAssign": "error",
+						"noSetterReturn": "error",
+						"noSwitchDeclarations": "error",
+						"noUndeclaredVariables": "error",
+						"noUnreachable": "error",
+						"noUnreachableSuper": "error",
+						"noUnsafeFinally": "error",
+						"noUnsafeOptionalChaining": "error",
+						"noUnusedLabels": "error",
+						"noUnusedPrivateClassMembers": "error",
+						"noUnusedVariables": "error",
+						"useIsNan": "error",
+						"useValidForDirection": "error",
+						"useValidTypeof": "error",
+						"useYield": "error"
+					},
+					"suspicious": {
+						"noAssignInExpressions": "error",
+						"noAsyncPromiseExecutor": "error",
+						"noCatchAssign": "error",
+						"noClassAssign": "error",
+						"noCompareNegZero": "error",
+						"noConstantBinaryExpressions": "error",
+						"noControlCharactersInRegex": "error",
+						"noDebugger": "error",
+						"noDuplicateCase": "error",
+						"noDuplicateClassMembers": "error",
+						"noDuplicateElseIf": "error",
+						"noDuplicateObjectKeys": "error",
+						"noDuplicateParameters": "error",
+						"noEmptyBlockStatements": "error",
+						"noFallthroughSwitchClause": "error",
+						"noFunctionAssign": "error",
+						"noGlobalAssign": "error",
+						"noImportAssign": "error",
+						"noIrregularWhitespace": "error",
+						"noMisleadingCharacterClass": "error",
+						"noPrototypeBuiltins": "error",
+						"noRedeclare": "error",
+						"noShadowRestrictedNames": "error",
+						"noSparseArray": "error",
+						"noUnsafeNegation": "error",
+						"noUselessRegexBackrefs": "error",
+						"noWith": "error",
+						"useGetterReturn": "error"
+					}
+				}
+			}
+		},
+		{
+			"includes": ["**/*.ts", "**/*.tsx", "**/*.mts", "**/*.cts"],
+			"linter": {
+				"rules": {
+					"complexity": { "noArguments": "error" },
+					"correctness": {
+						"noConstAssign": "off",
+						"noGlobalObjectCalls": "off",
+						"noInvalidBuiltinInstantiation": "off",
+						"noInvalidConstructorSuper": "off",
+						"noSetterReturn": "off",
+						"noUndeclaredVariables": "off",
+						"noUnreachable": "off",
+						"noUnreachableSuper": "off"
+					},
+					"style": { "useConst": "error", "useSpreadOverApply": "error" },
+					"suspicious": {
+						"noClassAssign": "off",
+						"noDuplicateClassMembers": "off",
+						"noDuplicateObjectKeys": "off",
+						"noDuplicateParameters": "off",
+						"noFunctionAssign": "off",
+						"noImportAssign": "off",
+						"noRedeclare": "off",
+						"noUnsafeNegation": "off",
+						"noVar": "error",
+						"noWith": "off",
+						"useGetterReturn": "off"
+					}
+				}
+			}
+		}
+	]
+}

package.json

@@ -9,8 +9,8 @@
     "migration:cosmetics:run": "bun run src/scripts/run-cosmetics-migrations.ts",
     "migration:cosmetics:revert": "bun run src/scripts/run-cosmetics-migrations.ts --revert",
     "seed:cosmetics": "bun run src/scripts/seed-cosmetics.ts",
-    "lint": "eslint --ignore-pattern .gitignore .",
-    "lint:fix": "bun run lint -- --fix",
+    "lint": "biome lint .",
+    "lint:fix": "biome lint --write .",
     "prepare": "if [ \"$NODE_ENV\" != \"production\" ]; then husky install; fi",
     "build": "tsc"
   },
@@ -31,22 +31,18 @@
     "typeorm": "^0.3.28"
   },
   "devDependencies": {
+    "@biomejs/biome": "2.5.0",
     "@commitlint/cli": "^20.4.1",
     "@commitlint/config-conventional": "^20.4.1",
-    "@eslint/eslintrc": "^3.3.3",
-    "@eslint/js": "^9.39.2",
     "@faker-js/faker": "^10.2.0",
     "@types/autocannon": "^7.12.7",
     "@types/jsonwebtoken": "^9.0.10",
     "autocannon": "^8.0.0",
     "bun-types": "^1.3.8",
-    "eslint": "^9.39.2",
-    "globals": "^16.5.0",
     "husky": "^9.1.7",
     "install": "^0.13.0",
     "lint-staged": "^16.2.7",
-    "typescript": "5.9.3",
-    "typescript-eslint": "^8.54.0"
+    "typescript": "5.9.3"
   },
   "overrides": {
     "axios": "^1.18.0",
@@ -55,6 +51,6 @@
   },
   "module": "src/index.js",
   "lint-staged": {
-    "*.(js|ts)": "npm run lint:fix"
+    "*.{js,ts}": "biome lint --write --no-errors-on-unmatched"
   }
 }

src/modules/wrapped/infrastructure/WrappedPostgresRepository.ts

@@ -196,7 +196,7 @@ export class WrappedPostgresRepository implements WrappedRepository {
         );
 
         return results.map(
-            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            // biome-ignore lint/suspicious/noExplicitAny: raw SQL query rows are untyped
             (row: any) =>
                 new BanListStats(
                     row.ban_list_name,
@@ -334,7 +334,7 @@ export class WrappedPostgresRepository implements WrappedRepository {
             [playerId, seasonId],
         );
 
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        // biome-ignore lint/suspicious/noExplicitAny: raw SQL query rows are untyped
         return results.map((row: any) => ({
             id: row.id,
             name: row.name,

src/modules/wrapped/infrastructure/themes/AbstractThemeStrategy.ts

@@ -33,7 +33,6 @@ export abstract class AbstractThemeStrategy implements IThemeStrategy {
         };
     }
 
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     renderSpecialSections(_data: SeasonWrapped, _options: GenerateOptions, _background: string): string {
         return "";
     }

src/shared/logger/infrastructure/Pino.ts

@@ -13,6 +13,7 @@ export class Pino implements Logger {
 		},
 	});
 
+	// biome-ignore lint/correctness/noUnusedPrivateClassMembers: reserved for file logging, currently disabled (see commented calls in log methods)
 	private readonly fileLogger = pino({
 		level: "debug",
 		transport: {

tests/unit/modules/auth/application/UserAuth.test.ts

@@ -21,13 +21,13 @@ describe("UserAuth", () => {
     jwt = new JWT({ issuer: "issuer", secret: "secret" });
 
     repository = {
-      create: async () => { },
+      create: async () => undefined,
       findByEmailOrUsername: async () => null,
       findByEmail: async () => null,
       findByUsername: async () => null,
       findById: async () => null,
-      update: async () => { },
-      updateParticipantId: async () => { },
+      update: async () => undefined,
+      updateParticipantId: async () => undefined,
       findByParticipantId: async () => null,
     };
 

tests/unit/modules/catalog/application/GetCosmeticsCatalog.test.ts

@@ -224,12 +224,10 @@ describe("GetCosmeticsCatalog", () => {
 		// Use a spy gatekeeper to count accessFor calls.
 		let accessForCalls = 0;
 		const spyGk = {
-			// eslint-disable-next-line @typescript-eslint/no-unused-vars
 			accessFor: async (_userId: string | null) => {
 				accessForCalls++;
 				return new CosmeticAccess(CosmeticTier.REGISTERED, new Set());
 			},
-			// eslint-disable-next-line @typescript-eslint/no-unused-vars
 			canUse: async (_userId: string, _c: { id: string; tier: CosmeticTier }) => false,
 		} as unknown as EntitlementsGatekeeper;