Chore: make ESLint and TypeScript happy

Build/lib/fetch-retry.ts

@@ -139,10 +139,6 @@ export class ResponseError<T extends UndiciResponseData | Response> extends Erro
     const statusCode = 'statusCode' in res ? res.statusCode : res.status;
     super('HTTP ' + statusCode + ' ' + args.map(_ => inspect(_)).join(' '));
 
-    if ('captureStackTrace' in Error) {
-      Error.captureStackTrace(this, ResponseError);
-    }
-
     // eslint-disable-next-line sukka/unicorn/custom-error-definition -- deliberatly use previous name
     this.name = this.constructor.name;
     this.res = res;

Build/lib/rules/base.ts

@@ -25,7 +25,7 @@ export class FileOutput {
 
   protected domainKeywords = new Set<string>();
 
-  private whitelistKeywords = new Set<string>();
+  private readonly whitelistKeywords = new Set<string>();
 
   protected userAgent = new Set<string>();
   protected processName = new Set<string>();

Build/lib/writing-strategy/singbox.ts

@@ -35,7 +35,7 @@ export class SingboxSource extends BaseWriteStrategy {
 
   static readonly jsonToLines = (json: unknown): string[] => stringify(json).split('\n');
 
-  private singbox: SingboxHeadlessRule = {
+  private readonly singbox: SingboxHeadlessRule = {
     domain: [MARKER_DOMAIN],
     domain_suffix: [MARKER_DOMAIN]
   };

Build/lib/writing-strategy/surge.ts

@@ -148,7 +148,7 @@ export class SurgeMitmSgmodule extends BaseWriteStrategy {
   readonly fileExtension = 'sgmodule';
   readonly type = '';
 
-  private rules = new Set<string>();
+  private readonly rules = new Set<string>();
 
   protected get result() {
     if (this.rules.size === 0) {