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# TypeScript ESLint Plugin TSLint
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TypeScript ESLint Plugin TSLint is an ESLint plugin that provides a bridge between ESLint and TSLint by wrapping TSLint configurations and enabling the use of TSLint rules within an ESLint workflow. It allows developers to gradually migrate from TSLint to ESLint while maintaining existing TSLint rules and configurations.
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## Package Information
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- **Package Name**: @typescript-eslint/eslint-plugin-tslint
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- **Package Type**: npm
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- **Language**: TypeScript
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- **Installation**: `npm install @typescript-eslint/eslint-plugin-tslint`
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## Core Imports
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```typescript
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// When using the plugin programmatically
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import { meta, rules } from "@typescript-eslint/eslint-plugin-tslint";
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// or
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import * as eslintPluginTslint from "@typescript-eslint/eslint-plugin-tslint";
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```
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For CommonJS:
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```javascript
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const { meta, rules } = require("@typescript-eslint/eslint-plugin-tslint");
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// or
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const eslintPluginTslint = require("@typescript-eslint/eslint-plugin-tslint");
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```
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## Basic Usage
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```typescript
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// ESLint configuration (.eslintrc.js)
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module.exports = {
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  parser: "@typescript-eslint/parser",
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  parserOptions: {
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    project: "./tsconfig.json"
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  },
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  plugins: ["@typescript-eslint/tslint"],
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  rules: {
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    "@typescript-eslint/tslint/config": [
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      "error",
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      {
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        rules: {
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          semicolon: [true, "always"],
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          "no-string-throw": true
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        }
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      }
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    ]
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  }
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};
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```
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## Architecture
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The plugin is built around these key components:
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- **Plugin Metadata**: Contains name and version information exported as `meta`
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- **Single Rule System**: Exposes only one rule called "config" that wraps TSLint functionality
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- **Custom Linter**: Extends TSLint's Linter class to integrate with TypeScript compiler program
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- **Configuration Bridge**: Converts ESLint configuration to TSLint configuration format
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- **Result Transformation**: Converts TSLint failures to ESLint report format with auto-fixing support
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## Capabilities
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### Plugin Metadata
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The plugin exports metadata information containing the plugin name and version.
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```typescript { .api }
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import type { Linter } from '@typescript-eslint/utils/ts-eslint';
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export const meta: Linter.PluginMeta;
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// Linter.PluginMeta is defined in @typescript-eslint/utils/ts-eslint
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// and contains:
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// {
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//   name: string;
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//   version: string;
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// }
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```
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### Plugin Rules
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The plugin exports a rules object containing the single "config" rule.
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```typescript { .api }
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import type { Linter } from '@typescript-eslint/utils/ts-eslint';
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export const rules: Linter.PluginRules;
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// The rules object contains a single rule:
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// {
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//   config: ESLintRule
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// }
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```
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### TSLint Configuration Rule
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The main rule that wraps TSLint configuration and applies TSLint rules through ESLint.
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```typescript { .api }
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// Rule name: "config"
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// Usage: "@typescript-eslint/tslint/config"
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interface RuleOptions {
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  /** TSLint rules configuration */
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  rules?: RawRulesConfig;
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  /** Custom TSLint rules directories */
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  rulesDirectory?: string[];
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  /** Path to TSLint configuration file */
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  lintFile?: string;
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}
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type RawRulesConfig = Record<
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  string,
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  | unknown[]
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  | boolean
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  | {
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      severity?: RuleSeverity | 'default' | 'none' | 'warn';
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      options?: unknown;
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    }
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  | null
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  | undefined
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>;
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type RuleSeverity = 'error' | 'warning' | 'info' | 'hint';
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```
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**Usage Examples:**
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```typescript
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// Inline rules configuration
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{
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  "@typescript-eslint/tslint/config": [
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    "error",
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    {
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      rules: {
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        semicolon: [true, "always"],
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        "no-string-throw": true,
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        "restrict-plus-operands": true
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      }
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    }
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  ]
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}
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// External TSLint file configuration
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{
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  "@typescript-eslint/tslint/config": [
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    "error",
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    {
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      lintFile: "./tslint.json"
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    }
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  ]
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}
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// Custom rules directory
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{
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  "@typescript-eslint/tslint/config": [
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    "error",
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    {
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      rulesDirectory: ["./custom-tslint-rules"],
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      rules: {
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        "custom-rule": {
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          severity: "error",
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          options: { customOption: true }
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        }
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      }
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    }
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  ]
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}
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```
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### Custom Linter Class
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Extended TSLint Linter class that provides access to TypeScript compiler program.
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```typescript { .api }
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import type { ILinterOptions, LintResult } from 'tslint';
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import { Linter } from 'tslint';
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import type { Program, SourceFile } from 'typescript';
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class CustomLinter extends Linter {
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  constructor(
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    options: ILinterOptions,
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    private readonly program: Program
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  );
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  /** Get the linting results from TSLint */
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  getResult(): LintResult;
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  /** Get a TypeScript source file from the program */
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  getSourceFile(fileName: string): SourceFile | undefined;
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}
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// ILinterOptions and LintResult are imported from 'tslint'
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// Program and SourceFile are imported from 'typescript'
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```
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## Types
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```typescript { .api }
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type MessageIds = 'failure';
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type Options = [
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  {
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    rules?: RawRulesConfig;
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    rulesDirectory?: string[];
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    lintFile?: string;
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  }
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];
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```
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## Error Handling
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The plugin handles errors by:
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- Converting TSLint rule failures to ESLint diagnostic messages
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- Preserving original TSLint error messages and rule names
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- Maintaining source location information for precise error reporting
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- Supporting auto-fix suggestions from TSLint rules when available
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Common error scenarios:
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- Missing `parserOptions.project` configuration (required for TypeScript parsing)
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- TSLint configuration file not found when using `lintFile` option
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- Custom rules directory path not found when using `rulesDirectory`
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- TSLint rule configuration errors (invalid rule names or options)
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## Dependencies
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### Peer Dependencies
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- **eslint**: `^8.56.0` - ESLint linting framework  
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- **tslint**: `^5.0.0 || ^6.0.0` - TSLint linting library
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- **typescript**: `*` - TypeScript compiler
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### Internal Dependencies  
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- **@typescript-eslint/utils**: `7.0.2` - TypeScript ESLint utilities
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## Installation and Setup
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```bash
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npm install @typescript-eslint/eslint-plugin-tslint tslint typescript
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```
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Required ESLint configuration:
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```javascript
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module.exports = {
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  parser: "@typescript-eslint/parser",
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  parserOptions: {
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    project: "./tsconfig.json", // Required for TypeScript parsing
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    ecmaVersion: 2018,
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    sourceType: "module"
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  },
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  plugins: ["@typescript-eslint/tslint"],
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  rules: {
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    "@typescript-eslint/tslint/config": [
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      "error",
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      {
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        // TSLint configuration options
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      }
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    ]
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  }
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};
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```