NestJS Server Development Expert

Ecosystem Context

Developers typically work in a Lerna fullstack monorepo created via lt fullstack init:

project/
├── projects/
│   ├── api/    ← nest-server-starter (depends on @lenne.tech/nest-server)
│   └── app/    ← nuxt-base-starter (depends on @lenne.tech/nuxt-extensions)
├── lerna.json
└── package.json (workspaces: ["projects/*"])

Package relationships:

• nest-server-starter (template) → depends on @lenne.tech/nest-server (core package)
• nuxt-base-starter (template) → depends on @lenne.tech/nuxt-extensions → aligned with nest-server
• This skill covers projects/api/ and any code depending on @lenne.tech/nest-server

When to Use This Skill

• Creating/modifying NestJS modules, services, controllers, resolvers, models
• Running/debugging the NestJS server (pnpm start, pnpm run dev, pnpm test)
• Using lt server module, lt server object, lt server addProp, lt server create
• Creating API tests for controllers/resolvers
• Analyzing existing NestJS code, architecture, relationships
• Answering NestJS/@lenne.tech/nest-server questions

Rule: If it involves NestJS or @lenne.tech/nest-server in ANY way, use this skill!

Skill Boundaries

User Intent	Correct Skill
"Create a NestJS module"	THIS SKILL
"Debug a service error"	THIS SKILL
"Add a REST endpoint"	THIS SKILL
"Update nest-server to v14"	nest-server-updating
"Write tests first, then implement"	building-stories-with-tdd
"Update npm packages"	maintaining-npm-packages
"Build a Vue component"	developing-lt-frontend
"Run lt fullstack init"	using-lt-cli

Related Skills & Commands

• developing-lt-frontend - For ALL Nuxt/Vue frontend development (projects/app/)
• building-stories-with-tdd - For TDD workflow (tests first, then implementation)
• using-lt-cli - For Git operations and Fullstack initialization
• nest-server-updating - For updating @lenne.tech/nest-server versions
• /lt-dev:review - General security review of branch diff
• /lt-dev:backend:sec-review - Security review after implementing endpoints or modifying auth/authz
• /lt-dev:backend:sec-audit - Full OWASP security audit for dependencies, config, and code

In monorepo projects:

• projects/api/ or packages/api/ → This skill
• projects/app/ or packages/app/ → developing-lt-frontend

CRITICAL RULES

CLI-First Development

When creating new modules, objects, or adding properties, use lt server CLI commands first before writing code manually. The CLI generates complete, standards-compliant scaffolding with all decorators, imports, and module integration.

# Always add --noConfirm --skipLint for non-interactive execution
lt server module --name Product --controller Rest --noConfirm --skipLint \
  --prop-name-0 name --prop-type-0 string \
  --prop-name-1 price --prop-type-1 number

lt server object --name Address --noConfirm --skipLint \
  --prop-name-0 city --prop-type-0 string

lt server addProp --type Module --element User --noConfirm --skipLint \
  --prop-name-0 avatar --prop-type-0 string --prop-nullable-0 true

After CLI scaffolding, customize the generated code: business logic, security rules (securityCheck), descriptions, and custom methods.

Complete flag reference: reference/configuration.md

Security (NON-NEGOTIABLE)

1. NEVER remove/weaken @Restricted() or @Roles() decorators
2. NEVER modify securityCheck() to bypass security
3. ALWAYS analyze permissions BEFORE writing tests
4. ALWAYS test with the LEAST privileged authorized user
5. VERIFY decorator coverage with lt server permissions after creating modules

Complete security rules: reference/security-rules.md | OWASP checklist: reference/owasp-checklist.md

Never Use declare Keyword

// WRONG - Decorator won't work!
declare name: string;

// CORRECT
@UnifiedField({ description: 'Product name' })
name: string;

Details: reference/declare-keyword-warning.md

Description Management

Apply descriptions consistently to EVERY component (Model, CreateInput, UpdateInput, Objects, Class-level decorators). Format: 'English text' or 'English (Deutsch)' for German input.

Complete guide: reference/description-management.md

Quick Command Reference

# Create module (REST is default!) — always use --noConfirm --skipLint
lt server module --name Product --controller Rest --noConfirm --skipLint

# Create SubObject
lt server object --name Address --noConfirm --skipLint

# Add properties
lt server addProp --type Module --element User --noConfirm --skipLint

# New project
lt server create <server-name> --noConfirm

# Permissions report (audit @Roles, @Restricted, securityCheck)
lt server permissions --format html --open
lt server permissions --format json --output permissions.json
lt server permissions --failOnWarnings  # CI/CD mode

API Style: REST is default. Use --controller GraphQL only when explicitly requested.

Complete configuration & property flags: reference/configuration.md

TDD Recommendation

1. Write API tests FIRST (REST/GraphQL endpoint tests)
2. Implement backend code until tests pass
3. Iterate until all tests green
4. Then proceed to frontend (E2E tests first)

For full TDD workflow orchestration, use building-stories-with-tdd skill.

Test Cleanup (CRITICAL)

afterAll(async () => {
  await db.collection('entities').deleteMany({ createdBy: testUserId });
  await db.collection('users').deleteMany({ email: /@test\.com$/ });
});

Use separate test database: app-test instead of app-dev

Framework Essentials

• Read CrudService before modifying any Service (node_modules/@lenne.tech/nest-server/src/core/common/services/crud.service.ts)
• NEVER blindly pass all serviceOptions to other Services (only pass currentUser)
• Check if CrudService already provides needed functionality

Complete framework guide: reference/framework-guide.md

Workflow (7 Phases)

1. Analysis & Planning - Parse spec, create todo list
2. SubObject Creation - Create in dependency order
3. Module Creation - Create with all properties
4. Inheritance Handling - Update extends, CreateInput must include parent fields
5. Description Management - Extract from comments, apply everywhere
6. Enum File Creation - Manual creation in src/server/common/enums/
7. API Test Creation - Analyze permissions first, use least privileged user

Complete workflow: reference/workflow-process.md

Property Ordering

ALL properties must be in alphabetical order in Model, Input, and Output files.

Permissions Report

The @lenne.tech/nest-server includes a built-in permissions scanner that audits @Roles, @Restricted, and securityCheck() usage across all modules.

• CLI: lt server permissions (generates MD/JSON/HTML report via AST scan — preferred)
• Runtime: Enable permissions: true in config.env.ts for a live dashboard at GET /permissions

The scanner detects: missing class-level @Restricted, endpoints without @Roles, models without securityCheck(), unrestricted fields, and unrestricted methods. Use after creating new modules to verify decorator coverage.

Verification Checklist

• All components created with descriptions (Model + CreateInput + UpdateInput)
• Properties in alphabetical order
• Permission analysis BEFORE writing tests
• Least privileged user used in tests
• Security validation tests (401/403 failures)
• Permissions report shows no new warnings (lt server permissions --failOnWarnings)
• Security review passed (/lt-dev:backend:sec-review)
• All tests pass

Complete checklist: reference/verification-checklist.md

Reference Files

Topic	File
Permissions Report	Built-in: lt server permissions / GET /permissions
Service Health Check	reference/service-health-check.md
Framework Guide	reference/framework-guide.md
Configuration & Commands	reference/configuration.md
Specification Format	reference/reference.md
Examples	reference/examples.md
Workflow Process	reference/workflow-process.md
Description Management	reference/description-management.md
Security Rules	reference/security-rules.md
OWASP Checklist	reference/owasp-checklist.md
Declare Keyword Warning	reference/declare-keyword-warning.md
Quality Review	reference/quality-review.md
Verification Checklist	reference/verification-checklist.md
TypeScript Conventions	reference/typescript-conventions.md

TypeScript Language Server (Recommended)

Operation	Use Case
goToDefinition	Find where a class/function/type is defined
findReferences	Find all usages of a symbol
hover	Get type info and documentation
documentSymbol	List all symbols in a file
workspaceSymbol	Search symbols across the project
goToImplementation	Find implementations of interfaces
incomingCalls / outgoingCalls	Analyze call dependencies