Type Checking

The types command runs TypeScript’s type checker on your Native Desktop project to validate type safety, catch type errors, and ensure your code adheres to TypeScript’s type system without emitting any output files.

Prerequisites

Before running the types command, ensure:

Your project has been created using native-desktop create
All dependencies are installed (npm install)
TypeScript configuration exists (tsconfig.json)
Your project uses TypeScript (.ts or .tsx files)

Basic Usage

To check TypeScript types in your project, open the terminal in the root directory of your Native Desktop project and run:

native-desktop types

This command will:

Load TypeScript configuration from tsconfig.json
Analyze all TypeScript files in your project
Check for type errors and inconsistencies
Report any type-related issues
Exit with an appropriate status code

What Gets Checked

By default, the types command checks:

All TypeScript files (.ts, .tsx)
Type definitions (.d.ts files)
Files in the src/ directory
Files specified in tsconfig.json include patterns

Files and directories specified in tsconfig.json exclude patterns are automatically skipped.

Output Examples

Successful Type Check (No Errors)

$ native-desktop types

✓ Type checking complete
✓ No type errors found
All TypeScript types are valid

With Type Errors

$ native-desktop types

✖ Type checking failed: 3 errors found

src/components/Button.tsx:15:7
  Type 'string' is not assignable to type 'number'.
  15   const count: number = "hello";
           ~~~~~

src/utils/helpers.ts:23:16
  Property 'name' does not exist on type 'User'.
  23   return user.name;
                  ~~~~

src/index.ts:45:10
  Argument of type 'boolean' is not assignable to parameter of type 'string'.
  45   myFunction(true);
          ~~~~

✖ Found 3 type errors

With Warnings

$ native-desktop types

⚠ Type checking complete with warnings

src/models/User.ts:12:5
  'age' is declared but its value is never read.
  12   age: number;
       ~~~

✓ 0 errors, 1 warning

TypeScript Configuration

The types command uses the tsconfig.json file generated by native-desktop create. Here’s an example configuration:

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "lib": ["ES2022"],
    "moduleResolution": "node",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true,
    "noEmit": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "bin", "dist"]
}

TypeScript Compiler Options

Common compiler options that affect type checking:

Strict Checks
Error Detection
Module Resolution
Other Options

strict: Enable all strict type-checking options
noImplicitAny: Error on expressions with implied any type
strictNullChecks: Enable strict null checking
strictFunctionTypes: Enable strict checking of function types
strictBindCallApply: Enable strict checking of bind, call, and apply
strictPropertyInitialization: Ensure class properties are initialized

noUnusedLocals: Report errors on unused local variables
noUnusedParameters: Report errors on unused parameters
noImplicitReturns: Report error when function doesn’t return value
noFallthroughCasesInSwitch: Report errors for fallthrough cases in switch
noUncheckedIndexedAccess: Add undefined to unverified index signatures

moduleResolution: Specify module resolution strategy (node, classic)
esModuleInterop: Enable interoperability between CommonJS and ES Modules
resolveJsonModule: Allow importing JSON files
allowSyntheticDefaultImports: Allow default imports from modules with no default export

Common Type Errors

Type Mismatch

Error: Type 'X' is not assignable to type 'Y'Cause: You’re trying to assign a value of one type to a variable of another type.Solution: Ensure the types match or use type assertions/conversions.

// ❌ Error
const count: number = "hello";

// ✅ Fixed
const count: number = 42;

Property Does Not Exist

Error: Property 'X' does not exist on type 'Y'Cause: You’re accessing a property that doesn’t exist on the object’s type.Solution: Add the property to the type definition or use optional chaining.

// ❌ Error
interface User {
  name: string;
}
const user: User = { name: "John" };
console.log(user.age);

// ✅ Fixed
interface User {
  name: string;
  age?: number;
}
const user: User = { name: "John" };
console.log(user.age);

Implicit Any

Error: Parameter 'X' implicitly has an 'any' typeCause: TypeScript can’t infer the type and no explicit type is provided.Solution: Add explicit type annotations.

// ❌ Error
function greet(name) {
  return `Hello, ${name}`;
}

// ✅ Fixed
function greet(name: string): string {
  return `Hello, ${name}`;
}

Null or Undefined Error

Error: Object is possibly 'null' or 'undefined'Cause: You’re accessing a property on a value that might be null or undefined.Solution: Add null checks or use optional chaining.

// ❌ Error
function getLength(text: string | null) {
  return text.length;
}

// ✅ Fixed
function getLength(text: string | null) {
  return text?.length ?? 0;
}

Missing Return Statement

Error: Function lacks ending return statementCause: A function with a non-void return type doesn’t return a value in all code paths.Solution: Ensure all code paths return a value.

// ❌ Error
function getValue(flag: boolean): number {
  if (flag) {
    return 42;
  }
  // Missing return for else case
}

// ✅ Fixed
function getValue(flag: boolean): number {
  if (flag) {
    return 42;
  }
  return 0;
}

Integration with Development Workflow

Pre-Commit Hook

Add type checking to your pre-commit hooks:

{
  "husky": {
    "hooks": {
      "pre-commit": "native-desktop types && native-desktop lint"
    }
  }
}

CI/CD Pipeline

Include type checking in your continuous integration:

# GitHub Actions example
- name: Type Check
  run: native-desktop types

npm Scripts

Add type checking to your package.json scripts:

{
  "scripts": {
    "typecheck": "native-desktop types",
    "test": "native-desktop types && npm run test:unit",
    "validate": "native-desktop types && native-desktop lint && native-desktop fmt"
  }
}

Exit Codes

The types command uses standard exit codes for CI/CD integration:

0: No type errors found
1: Type errors found

native-desktop types
echo $?  # Check exit code

Common Issues

TypeScript Configuration Not Found

Error: Cannot find tsconfig.jsonSolution: Ensure the configuration file exists in your project root.

# Check if file exists
ls -la tsconfig.json

# If missing, create a basic configuration
npx tsc --init

Cannot Find Module

Error: Cannot find module 'xyz'Solution: Install missing type definitions or dependencies.

# Install missing types
npm install --save-dev @types/node

# Or install the actual package
npm install xyz

Too Many Type Errors

Error: Overwhelmed by type errors in a new projectSolution: Fix errors gradually or adjust strictness settings temporarily.

{
  "compilerOptions": {
    "strict": false,  // Temporarily disable strict mode
    "noImplicitAny": false
  }
}

Type Definitions Conflict

Error: Conflicting type definitionsSolution: Check for duplicate type packages or version mismatches.

# List installed type packages
npm list @types

# Remove duplicates
npm uninstall @types/xyz
npm install --save-dev @types/xyz@latest

Out of Memory Error

Error: JavaScript heap out of memorySolution: Increase Node.js memory limit or exclude large directories.

# Increase memory limit
NODE_OPTIONS="--max-old-space-size=4096" native-desktop types

Update tsconfig.json:

{
  "exclude": ["node_modules", "bin", "dist", "large-folder"]
}

Customizing Type Checking

You can customize TypeScript’s behavior in tsconfig.json:

{
  "compilerOptions": {
    // Enable strict type checking
    "strict": true,
    
    // Report errors for unused variables
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    
    // Require explicit return types
    "noImplicitReturns": true,
    
    // Check indexed access
    "noUncheckedIndexedAccess": true,
    
    // Skip checking of declaration files
    "skipLibCheck": true,
    
    // Do not emit output
    "noEmit": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "**/*.spec.ts"]
}

IDE Integration

Most modern IDEs provide built-in TypeScript support:

Visual Studio Code

TypeScript support is built-in. Configure in settings.json:

{
  "typescript.tsdk": "node_modules/typescript/lib",
  "typescript.enablePromptUseWorkspaceTsdk": true,
  "typescript.updateImportsOnFileMove.enabled": "always",
  "editor.codeActionsOnSave": {
    "source.organizeImports": true
  }
}

WebStorm / IntelliJ IDEA

TypeScript support is built-in and enabled by default. Settings → Languages & Frameworks → TypeScript

Enable TypeScript Language Service
Use project’s TypeScript version

Type Checking Specific Files

While the CLI command checks the entire project, you can check specific files using tsc directly:

# Check specific file
npx tsc --noEmit src/index.ts

# Check specific directory
npx tsc --noEmit src/components/*.ts

# Check with different config
npx tsc --noEmit -p tsconfig.production.json

Watch Mode

For continuous type checking during development, use TypeScript’s watch mode:

# Run TypeScript compiler in watch mode
npx tsc --noEmit --watch

This will continuously check types as you make changes to your code.

Best Practices

Enable Strict Mode

Use "strict": true for maximum type safety and error prevention.

Type Everything

Add explicit type annotations, especially for function parameters and return types.

Check Regularly

Run type checking frequently during development to catch errors early.

Fix Incrementally

When facing many errors, fix them incrementally rather than all at once.

Type Safety Levels

Different levels of type strictness you can configure:

Relaxed (Not Recommended)
Standard
Strict (Recommended)

{
  "compilerOptions": {
    "strict": false,
    "noImplicitAny": false,
    "skipLibCheck": true
  }
}

Easy to start, but provides minimal type safety.

{
  "compilerOptions": {
    "strict": true,
    "skipLibCheck": true
  }
}

Good balance between safety and ease of use.

{
  "compilerOptions": {
    "strict": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true
  }
}

Maximum type safety with comprehensive error checking.

Command Comparison

Command	Purpose	Auto-Fix	Type Checking
`native-desktop types`	Check TypeScript types	❌ No	✅ Yes
`native-desktop lint`	Check code quality	⚠️ Limited	❌ No
`native-desktop fmt`	Format code style	✅ Yes	❌ No

Use all three commands together for comprehensive code quality: types for type safety, lint for code quality, and fmt for consistent formatting.

Development Workflow

Recommended workflow for type-safe development:

Performance Optimization

For large projects, optimize type checking performance:

{
  "compilerOptions": {
    // Skip checking declaration files
    "skipLibCheck": true,
    
    // Use incremental compilation
    "incremental": true,
    
    // Specify output for incremental info
    "tsBuildInfoFile": ".tsbuildinfo"
  },
  "exclude": [
    "node_modules",
    "bin",
    "dist",
    "**/*.spec.ts"
  ]
}

Quick Start

Getting started

Tips and Tricks

User Guide

Prerequisites

Basic Usage

What Gets Checked

Output Examples

Successful Type Check (No Errors)

With Type Errors

With Warnings

TypeScript Configuration

TypeScript Compiler Options

Common Type Errors

Integration with Development Workflow

Pre-Commit Hook

CI/CD Pipeline

npm Scripts

Exit Codes

Common Issues

Customizing Type Checking

IDE Integration

Visual Studio Code

WebStorm / IntelliJ IDEA

Type Checking Specific Files

Watch Mode

Best Practices

Enable Strict Mode

Type Everything

Check Regularly

Fix Incrementally

Type Safety Levels

Command Comparison

Development Workflow

Performance Optimization

Quick Start

Getting started

Tips and Tricks

User Guide

​Prerequisites

​Basic Usage

​What Gets Checked

​Output Examples

​Successful Type Check (No Errors)

​With Type Errors

​With Warnings

​TypeScript Configuration

​TypeScript Compiler Options

​Common Type Errors

​Integration with Development Workflow

​Pre-Commit Hook

​CI/CD Pipeline

​npm Scripts

​Exit Codes

​Common Issues

​Customizing Type Checking

​IDE Integration

​Visual Studio Code

​WebStorm / IntelliJ IDEA

​Type Checking Specific Files

​Watch Mode

​Best Practices

Enable Strict Mode

Type Everything

Check Regularly

Fix Incrementally

​Type Safety Levels

​Command Comparison

​Development Workflow

​Performance Optimization

Prerequisites

Basic Usage

What Gets Checked

Output Examples

Successful Type Check (No Errors)

With Type Errors

With Warnings

TypeScript Configuration

TypeScript Compiler Options

Common Type Errors

Integration with Development Workflow

Pre-Commit Hook

CI/CD Pipeline

npm Scripts

Exit Codes

Common Issues

Customizing Type Checking

IDE Integration

Visual Studio Code

WebStorm / IntelliJ IDEA

Type Checking Specific Files

Watch Mode

Best Practices

Type Safety Levels

Command Comparison

Development Workflow

Performance Optimization