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# Library Integration
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Add external libraries to your NestJS project with automated setup, configuration, and integration. The add command streamlines the process of incorporating third-party packages and NestJS-specific libraries into your application.
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## Capabilities
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### Add Command
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Integrates external libraries with automated setup and configuration management.
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```bash { .api }
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# Add library to project
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nest add <library> [options] [library-specific-options]
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# Options:
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-d, --dry-run                       # Report actions without writing results
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-s, --skip-install                  # Skip package installation (default: false)
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-p, --project [project]             # Project in which to generate files
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[library-specific-options]         # Additional options passed to the library's schematic
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```
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**Usage Examples:**
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```bash
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# Add Swagger/OpenAPI support
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nest add @nestjs/swagger
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# Add GraphQL support
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nest add @nestjs/graphql
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# Add database integration
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nest add @nestjs/typeorm
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nest add @nestjs/mongoose
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# Add authentication
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nest add @nestjs/passport
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# Preview changes without installing
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nest add @nestjs/swagger --dry-run
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# Add to specific project in monorepo
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nest add @nestjs/swagger --project api-gateway
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# Skip automatic package installation
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nest add @nestjs/swagger --skip-install
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```
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## Supported Libraries
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### Core NestJS Libraries
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Official NestJS packages with automated integration:
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```bash { .api }
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# Web Framework Enhancements
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nest add @nestjs/swagger              # OpenAPI/Swagger documentation
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nest add @nestjs/graphql              # GraphQL API development
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nest add @nestjs/websockets           # WebSocket support
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nest add @nestjs/microservices        # Microservices architecture
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# Database Integration
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nest add @nestjs/typeorm              # TypeORM database integration
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nest add @nestjs/mongoose             # MongoDB with Mongoose
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nest add @nestjs/sequelize            # Sequelize ORM
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nest add @nestjs/prisma               # Prisma database toolkit
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# Authentication & Security
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nest add @nestjs/passport             # Passport authentication
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nest add @nestjs/jwt                  # JSON Web Token support
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nest add @nestjs/throttler            # Rate limiting
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# Caching & Performance
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nest add @nestjs/cache-manager        # Caching solutions
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nest add @nestjs/bull                 # Queue management
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nest add @nestjs/schedule             # Task scheduling
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# Monitoring & Logging
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nest add @nestjs/terminus             # Health checks
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nest add @nestjs/logger               # Enhanced logging
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# Configuration
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nest add @nestjs/config               # Configuration management
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nest add @nestjs/serve-static         # Static file serving
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```
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### Third-Party Libraries
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Many popular Node.js libraries with NestJS schematics:
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```bash { .api }
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# State Management
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nest add @ngrx/store                  # Redux-style state management
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# Validation
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nest add class-validator              # Decorator-based validation
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nest add joi                          # Schema validation
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# Testing
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nest add @nestjs/testing              # Enhanced testing utilities
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# Development Tools
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nest add @nestjs/devtools-integration # NestJS DevTools
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```
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## Library-Specific Options
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Many libraries accept additional configuration options during installation:
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### Swagger Integration
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```bash { .api }
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# Basic Swagger setup
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nest add @nestjs/swagger
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# With custom configuration
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nest add @nestjs/swagger --project api --title "My API" --version "1.0"
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```
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### GraphQL Setup
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```bash { .api }
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# Apollo GraphQL (default)
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nest add @nestjs/graphql
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# With schema-first approach
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nest add @nestjs/graphql --schemaFirst
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# With custom configuration
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nest add @nestjs/graphql --playground --introspection
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```
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### TypeORM Database
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```bash { .api }
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# Basic TypeORM setup
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nest add @nestjs/typeorm
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# With specific database
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nest add @nestjs/typeorm --database postgres
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nest add @nestjs/typeorm --database mysql
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nest add @nestjs/typeorm --database sqlite
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```
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## Installation Process
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### Automated Steps
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When adding a library, the CLI typically performs:
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1. **Package Installation**: Downloads and installs the library and its dependencies
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2. **Code Generation**: Creates configuration files and boilerplate code
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3. **Module Registration**: Updates app.module.ts or creates feature modules
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4. **Configuration Setup**: Adds necessary configuration files
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5. **Import Updates**: Updates import statements and module dependencies
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### Example: Adding Swagger
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```bash
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nest add @nestjs/swagger
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```
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**Generated Changes:**
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- Installs `@nestjs/swagger` and `swagger-ui-express`
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- Updates `main.ts` with Swagger configuration
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- Adds OpenAPI decorators to controllers
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- Creates Swagger documentation endpoint at `/api`
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### Example: Adding TypeORM
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```bash
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nest add @nestjs/typeorm
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```
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**Generated Changes:**
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- Installs `@nestjs/typeorm`, `typeorm`, and database driver
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- Creates `ormconfig.json` or database configuration
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- Updates `app.module.ts` with TypeORM module
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- Generates entity and repository examples
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- Sets up database connection configuration
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## Project Structure Impact
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### Configuration Files
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Added libraries often create configuration files:
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```
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project-root/
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├── ormconfig.json              # TypeORM configuration
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├── .env                        # Environment variables
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├── swagger-config.json         # Swagger configuration
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└── src/
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    ├── config/                 # Configuration modules
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    ├── entities/              # Database entities
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    └── modules/               # Feature modules
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```
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### Module Structure
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Libraries typically integrate into the module system:
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```typescript
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// app.module.ts after adding libraries
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@Module({
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  imports: [
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    ConfigModule.forRoot(),
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    TypeOrmModule.forRoot({
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      // Database configuration
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    }),
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    GraphQLModule.forRoot({
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      // GraphQL configuration
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    }),
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    // Other modules...
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  ],
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})
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export class AppModule {}
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```
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## Monorepo Support
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### Project-Specific Installation
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```bash { .api }
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# Add to specific application
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nest add @nestjs/swagger --project api-gateway
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nest add @nestjs/typeorm --project user-service
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# Add to shared library
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nest add @nestjs/common --project shared-utils
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```
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### Cross-Project Dependencies
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Some libraries can be shared across monorepo projects:
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```bash
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# Add shared authentication library
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nest add @nestjs/passport --project auth-lib
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# Add project-specific database connection
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nest add @nestjs/typeorm --project user-service
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```
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## Advanced Integration
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### Custom Schematics
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Some libraries provide custom schematics for advanced setup:
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```bash { .api }
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# Run specific library schematics
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nest add @my-org/custom-lib --schematic advanced-setup
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nest add @nestjs/graphql --schematic federation
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```
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### Configuration Options
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Pass configuration directly during installation:
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```bash { .api }
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# Complex configuration
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nest add @nestjs/typeorm \
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  --database postgres \
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  --host localhost \
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  --port 5432 \
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  --synchronize false
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```
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## Dry Run and Validation
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### Preview Changes
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```bash { .api }
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# See what would be changed
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nest add @nestjs/swagger --dry-run
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```
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**Dry Run Output:**
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- Lists files that would be created
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- Shows files that would be modified
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- Displays packages that would be installed
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- Previews configuration changes
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### Manual Installation
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```bash { .api }
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# Skip automatic package installation
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nest add @nestjs/swagger --skip-install
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# Then manually install
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npm install @nestjs/swagger swagger-ui-express
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```
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## Common Integration Patterns
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### API Documentation
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```bash { .api }
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# Complete API documentation setup
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nest add @nestjs/swagger
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nest add @nestjs/config  # For environment-based configuration
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```
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### Database with Auth
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```bash { .api }
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# Full backend setup
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nest add @nestjs/typeorm
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nest add @nestjs/passport
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nest add @nestjs/jwt
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nest add @nestjs/config
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```
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### GraphQL API
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```bash { .api }
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# GraphQL with database
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nest add @nestjs/graphql
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nest add @nestjs/typeorm
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nest add apollo-server-express
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```
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## Error Handling
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### Invalid Library Names
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```bash
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# Unknown library
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nest add unknown-library
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# Error: Schematic "ng-add" not found in collection "unknown-library"
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```
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### Dependency Conflicts
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The CLI detects and reports dependency conflicts:
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- Version incompatibilities
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- Peer dependency requirements
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- Duplicate installations
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### Installation Failures
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If package installation fails, the CLI:
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- Reports the specific error
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- Suggests manual installation steps
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- Provides rollback instructions
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- Preserves existing project state