Package Exports

embed-eslint
embed-eslint/lib/index.js

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Readme

embed-eslint

ESLint integration for embedded TypeScript compilation.

embed-eslint extends embed-typescript to provide seamless ESLint integration during TypeScript compilation. It allows you to apply ESLint rules and get linting feedback as part of the compilation process, all within your application runtime.

Features

Integrated linting: Apply ESLint rules during TypeScript compilation
Type-aware rules: Full support for @typescript-eslint rules that require type information
Unified diagnostics: ESLint violations are reported as TypeScript diagnostics
Zero configuration: Works out of the box with sensible defaults
Custom rules: Configure any ESLint rules you need

Installation

npm install embed-typescript embed-eslint 
npm install typescript 
npm install eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

Note: All of the following are peer dependencies that must be installed separately:

embed-typescript
typescript
eslint
@typescript-eslint/parser (>=6.0.0)
@typescript-eslint/eslint-plugin (>=6.0.0)

Quick Start

import { EmbedEsLint } from "embed-eslint";
import ts from "typescript";

// Create compiler with ESLint integration
const compiler = new EmbedEsLint({
  compilerOptions: {
    target: ts.ScriptTarget.ES2015,
    module: ts.ModuleKind.CommonJS,
    strict: true,
  },
  rules: {
    // TypeScript ESLint rules
    "@typescript-eslint/no-floating-promises": "error",
    "@typescript-eslint/no-unused-vars": "warn",
    "@typescript-eslint/explicit-function-return-type": "error",
    
    // Standard ESLint rules
    "no-console": "warn",
    "no-debugger": "error",
  },
});

// Compile and lint TypeScript code
const result = compiler.compile({
  "src/index.ts": `
    // This will trigger multiple ESLint violations
    async function fetchData() {
      console.log("Fetching data...");
      return { data: "test" };
    }
    
    fetchData(); // floating promise
    
    const unused = 42; // unused variable
  `
});

// Handle results
if (!result.success) {
  for (const diagnostic of result.diagnostics) {
    console.log(`${diagnostic.severity}: ${diagnostic.message}`);
    console.log(`  at ${diagnostic.file}:${diagnostic.start?.line}:${diagnostic.start?.column}`);
  }
}

Configuration

Constructor Options

The EmbedEsLint constructor extends all options from embed-typescript and adds:

interface IEmbedEsLintProps extends IEmbedTypeScriptProps {
  /**
   * ESLint rules configuration
   * Uses @typescript-eslint/eslint-plugin rules by default
   */
  rules?: Record<string, any>;
}

Available Rules

All rules from the following packages are available:

@typescript-eslint/eslint-plugin: TypeScript-specific rules
eslint: Core ESLint rules

Common useful rules:

{
  // Type-aware rules (require type information)
  "@typescript-eslint/no-floating-promises": "error",
  "@typescript-eslint/no-misused-promises": "error",
  "@typescript-eslint/await-thenable": "error",
  "@typescript-eslint/no-unnecessary-type-assertion": "warn",
  
  // Code quality rules
  "@typescript-eslint/no-unused-vars": "warn",
  "@typescript-eslint/explicit-function-return-type": "error",
  "@typescript-eslint/no-explicit-any": "warn",
  
  // Best practices
  "no-console": "warn",
  "no-debugger": "error",
  "eqeqeq": ["error", "always"],
}

Usage Examples

Basic Linting

import { EmbedEsLint } from "embed-eslint";

const compiler = new EmbedEsLint({
  rules: {
    "@typescript-eslint/no-unused-vars": "error",
  },
});

const result = compiler.compile({
  "test.ts": `
    const x = 1; // Error: 'x' is declared but never used
    const y = 2;
    console.log(y);
  `
});

With External Dependencies

import { EmbedEsLint } from "embed-eslint";
import external from "./external.json"; // Generated by embed-typescript CLI

const compiler = new EmbedEsLint({
  external,
  compilerOptions: {
    target: ts.ScriptTarget.ES2015,
    module: ts.ModuleKind.CommonJS,
  },
  rules: {
    "@typescript-eslint/no-floating-promises": "error",
  },
});

Custom Rule Severity

const compiler = new EmbedEsLint({
  rules: {
    // Different severity levels
    "@typescript-eslint/no-explicit-any": "warn",     // Warning
    "@typescript-eslint/no-unused-vars": "error",     // Error
    "no-console": "off",                              // Disabled
    
    // With options
    "@typescript-eslint/naming-convention": [
      "error",
      {
        selector: "interface",
        format: ["PascalCase"],
        prefix: ["I"],
      },
    ],
  },
});

How It Works

TypeScript Compilation: First compiles your TypeScript code using the embedded TypeScript compiler
ESLint Analysis: Passes the TypeScript AST and type information to ESLint
Unified Reporting: Converts ESLint messages to TypeScript diagnostics format
Single Pass: Both compilation and linting happen in a single operation

Differences from Standard ESLint

No filesystem access: Works entirely in memory
No config files: Configuration is passed programmatically
Integrated diagnostics: ESLint violations appear as TypeScript compilation errors
Type information: Automatically provides type information to rules that need it

Performance Considerations

ESLint analysis adds overhead to compilation time
For large codebases, consider enabling only essential rules
Type-aware rules are more expensive than syntax-only rules
Use skipLibCheck: true in compiler options for better performance

Troubleshooting

Rules not being applied

Ensure the rule names are correct and the severity is not "off":

// Correct
"@typescript-eslint/no-unused-vars": "error"

// Incorrect (missing namespace)
"no-unused-vars": "error" // This won't catch TypeScript-specific cases

Type-aware rules not working

Type-aware rules require proper TypeScript configuration:

const compiler = new EmbedEsLint({
  compilerOptions: {
    strict: true, // Enable strict type checking
    // ... other options
  },
  rules: {
    "@typescript-eslint/no-floating-promises": "error",
  },
});

Performance issues

Reduce the number of active rules
Disable type-aware rules if not needed
Use skipLibCheck: true in compiler options
Consider splitting large files

Contributing

Contributions are welcome! Please see the main embed-typescript repository for contribution guidelines.

License

MIT License - see the LICENSE file for details.

embed-eslint

Package Exports

Readme

embed-eslint

Features

Installation

Quick Start

Configuration

Constructor Options

Available Rules

Usage Examples

Basic Linting

With External Dependencies

Custom Rule Severity

How It Works

Differences from Standard ESLint

Performance Considerations

Troubleshooting

Rules not being applied

Type-aware rules not working

Performance issues

Contributing

License

See Also