ProPrompt for Developers

Target Audience: Software Developers, DevOps Engineers, Full-Stack Developers, and anyone who writes, reviews, or debugs code.

Getting Started – Your First Code Prompt
Writing & Refactoring Code
Debugging & Code Review
Advanced – Architecture & Complex Features
Agent: Autonomous Development in Agent Mode
Cheat Sheet for Developers

1 Getting Started – Your First Code Prompt

Difficulty: ⭐ Easy

The RICE framework applies to coding too – see Fundamentals.

Example – Generating a Simple Function

You are an experienced TypeScript developer.

Create a function `formatCurrency` that:
- Accepts an amount (number) and a currency (string, default "EUR")
- Returns the amount as a formatted string (e.g., "1,234.56 €")
- Uses English localization (en-US)
- Handles edge cases (NaN, negative values, undefined)

Output the function with JSDoc comments and 3 example calls.

Why does this work? Language, signature, behavior, and edge cases are clearly defined.

Copilot Chat – Slash Commands

Command	Function	Example
`/explain`	Explain code	`Explain #selection`
`/fix`	Fix errors	`Fix the type error in #file`
`/tests`	Generate tests	`Write tests for #selection`
`/doc`	Create docs	`Document #file with JSDoc`
`/new`	Scaffold new	`Create an Express project with TS`

Context Variables in Chat

Variable	Description
`#file:path/file.ts`	Reference a specific file
`#selection`	Reference selected code
`#editor`	Current editor content
`#codebase`	Search entire project
`#terminalLastCommand`	Last terminal command + output

2 Writing & Refactoring Code

Difficulty: ⭐⭐ Medium

Example – Refactoring with Clear Constraints

Refactor the function in #file:src/utils/parser.ts:

## Goal
The function is too long (85 lines) with too many nested if-blocks.

## Requirements
- Extract validation logic into a separate `validateInput()` function
- Use early returns instead of nested if-blocks
- Keep the existing signature
- Don't introduce new dependencies
- Existing tests must still pass

## Code Style
- Strict TypeScript (no `any`)
- Prefer functional patterns (map/filter/reduce)
- Max 20 lines per function

Example – API Endpoint with Full Context

You are a Senior Backend Developer.

## Context
- Framework: Express.js + TypeScript
- ORM: Prisma with PostgreSQL
- Auth: JWT via middleware in /src/middleware/auth.ts
- Existing structure:
  - /src/routes/ → Route handlers
  - /src/services/ → Business logic
  - /src/types/ → TypeScript interfaces

## Task
Create a CRUD endpoint for "Projects":

### Data Model
| Field | Type | Constraint |
|-------|------|-----------|
| id | UUID | PK, auto-generated |
| name | string | required, max 100 |
| description | string | optional, max 500 |
| status | enum | DRAFT, ACTIVE, ARCHIVED |
| ownerId | UUID | FK → User |
| createdAt | DateTime | auto |
| updatedAt | DateTime | auto |

### Endpoints
- `GET /api/v1/projects` – List (with pagination)
- `GET /api/v1/projects/:id` – Detail
- `POST /api/v1/projects` – Create (auth required)
- `PUT /api/v1/projects/:id` – Update (owner only)
- `DELETE /api/v1/projects/:id` – Delete (owner only)

### Requirements
- Input validation with zod
- Error handling with custom error classes
- Pagination: page, limit, sortBy, sortOrder
- All responses follow schema: { success, data, error?, meta? }

Visualization – Clean Architecture

flowchart TB
    subgraph API[" API Layer"]
        R[Routes] --> C[Controllers]
    end

    subgraph APP[" Application Layer"]
        C --> S[Services]
        S --> V[Validators]
    end

    subgraph DOMAIN[" Domain Layer"]
        S --> E[Entities]
        S --> I[Interfaces]
    end

    subgraph INFRA[" Infrastructure Layer"]
        I -.-> |implements| Repo[Repositories]
        Repo --> DB[(Database)]
        I -.-> |implements| Ext[External APIs]
    end

    style API fill:#e3f2fd
    style APP fill:#fff3e0
    style DOMAIN fill:#e8f5e9
    style INFRA fill:#fce4ec

3 Debugging & Code Review

Difficulty: ⭐⭐ Medium

Example – Systematic Debugging

The following error occurred: #terminalLastCommand

Analyze the error in the context of #file:src/app.ts.

## Task
1. Explain the root cause
2. Show the affected line(s)
3. Suggest a fix (as a diff)
4. Explain why the fix works
5. List potential follow-up issues

## Context
- Node.js 20, TypeScript 5.4
- Error occurs only in production (not locally)
- Recently changed files: #file:src/services/auth.ts

Example – Code Review Prompt

Review #selection for:

## Review Criteria
1. **Bugs** – Null references, race conditions, off-by-one errors
2. **Security** – Injection, XSS, insecure deserialization
3. **Performance** – N+1 queries, unnecessary computations, memory leaks
4. **Style** – Naming, DRY, Single Responsibility
5. **Testability** – Are dependencies injectable?

## Format
For each finding:
- Line(s)
- Problem
- Suggestion (as code)
- Severity: Critical / High / Medium / Low

Debugging Flowchart

flowchart TD
    A[🐛 Error Occurred] --> B{Error Type?}

    B --> C[🔴 Compile Error]
    B --> D[🟠 Runtime Error]
    B --> E[🟡 Logic Error]

    C --> C1["Check types<br/>Use /fix"]
    D --> D1[Read stack trace<br/>Set breakpoints]
    E --> E1[Write tests<br/>Compare input/output]

    C1 --> F[💡 Solution Found?]
    D1 --> F
    E1 --> F

    F -- Yes --> G[✅ Apply fix & test]
    F -- No --> H[🤖 Use Agent Mode<br/>with full context]

    style C fill:#ffcdd2
    style D fill:#ffe0b2
    style E fill:#fff9c4
    style G fill:#c8e6c9

4 Advanced – Architecture & Complex Features

Difficulty: ⭐⭐⭐ Hard

Example – System Design with AI

You are a Senior Software Architect.

## Task
Design the architecture for a real-time notification system.

## Requirements
- 50,000 concurrent users
- Push notifications (WebSocket + Mobile Push)
- Prioritization: Critical > High > Normal
- Delivery guarantee (at least once)
- Message history: 90 days

## Tech Constraints
- Cloud: Azure
- Backend: .NET 8
- Messaging: Azure Service Bus or Event Grid
- Database: Cosmos DB or PostgreSQL

## Desired Output
1. Architecture diagram (Mermaid)
2. Component descriptions (table)
3. Data flow diagram
4. Technology decisions with rationale
5. Scaling strategy

Example – Dockerfile with Multi-Stage Build

You are a Senior DevOps Engineer.

Create a Dockerfile for a Node.js 20 app:

## Context
- Package manager: pnpm
- Source directory: /src
- Build: TypeScript → JavaScript
- Port: 3000
- Health check: GET /health

## Requirements
- Multi-stage build (builder + runner)
- Non-root user
- Respect .dockerignore
- Only production dependencies in final image
- Alpine-based for minimal image size
- Labels per OCI standard

Output the Dockerfile with comments for each step.

5 Agent: Autonomous Development in Agent Mode

Difficulty: ⭐⭐⭐ Hard

What Can Agent Mode Do?

flowchart LR
    A[🧑‍💻 Developer<br/>gives prompt] --> B[🤖 Agent]
    B --> C[📁 Read files]
    B --> D[✏️ Write code]
    B --> E[🖥️ Run terminal]
    B --> F[🔍 Find errors]

    C & D & E & F --> G[🔄 Iterate<br/>until goal met]
    G --> H[✅ Result<br/>for review]

    style A fill:#e3f2fd
    style B fill:#fff3e0
    style H fill:#c8e6c9

When Agent vs. Chat?

Scenario	Agent ✅	Chat 💬
Feature across multiple files	✅
Refactor entire module	✅
Debugging with terminal	✅
Set up CI/CD pipeline	✅
Write a single function		💬 suffices
Get code explanation		💬 suffices
Quick regex		💬 suffices

Example – Agent Prompt: New Feature

## Goal
Implement a user authentication system with JWT.

## Context
- Express.js with TypeScript
- Prisma ORM with PostgreSQL
- Existing structure in /src/routes/ and /src/services/
- Tests with Jest in /src/__tests__/

## Steps
1. Create the Prisma schema for User (email, passwordHash, createdAt, role)
2. Create `src/services/authService.ts` with:
   - `register(email, password)` → hash password with bcrypt
   - `login(email, password)` → return JWT
   - `verifyToken(token)` → validate JWT
3. Create `src/middleware/auth.ts` → JWT middleware
4. Create `src/routes/auth.ts` → POST /register, POST /login
5. Add input validation with zod
6. Create tests in `src/__tests__/auth.test.ts`
7. Update `src/app.ts` with the new routes

## Requirements
- Hash passwords with bcrypt (12 rounds)
- JWT secret from environment variable
- Refresh token logic is NOT needed (coming later)
- Follow existing code conventions (#file:.github/copilot-instructions.md)

## Do Not
- No changes to existing routes
- Do not introduce a new ORM
- No changes to the DB connection

Agent Mode Best Practices

Tip	Description
📋 Instruction files	`.github/copilot-instructions.md` is loaded automatically
🎯 Limit scope	3 focused sessions > 1 massive session
🔍 Checkpoints	Review changes after each step
🖥️ Watch terminal	Agent runs commands – side effects possible
↩ Use undo	VS Code can revert agent changes
⚖️ Provide context	Reference relevant files with `#file:`

6 Cheat Sheet for Developers

Quick Prompt Templates

Task	Prompt
Write function	`"Create a [language] function that [description]. Signature: [signature]"`
Refactoring	`"Refactor #file: Extract [part] into separate function, use early returns"`
Fix bug	`"Analyze the error: #terminalLastCommand in context of #file"`
Tests	`"Write unit tests for #file with [framework]. Test happy path + edge cases"`
Code review	`"Review #selection for bugs, security, performance, and clean code"`
Documentation	`"Create JSDoc/XML documentation for all public members in #file"`
Create API	`"Create a REST endpoint for [resource] with [framework]"`
Dockerfile	`"Create a multi-stage Dockerfile for [app] with [runtime]"`
CI/CD	`"Create a GitHub Actions pipeline for [build + test + deploy]"`
Regex	`"Create a regex that matches [pattern]. Explain each part."`

Maximizing Copilot Context

┌────────────────────────────────────────┐
│ 1. .github/copilot-instructions.md │ ← Project rules (automatic)
│ 2. #file:relevant-file.ts │ ← Explicit context
│ 3. #codebase │ ← Project-wide search
│ 4. #terminalLastCommand │ ← Error context
│ 5. #selection │ ← Selected code
└────────────────────────────────────────┘

Context Checklist for Code Prompts

Language & version specified? (TypeScript 5.4, Python 3.11)
Framework named? (Express, React, .NET)
Existing patterns referenced? (Clean Architecture, Repository Pattern)
Signature/interface defined?
Edge cases listed?
Do Not clearly stated?
Test expectations specified?

Back to overview: 🏠 Home · Fundamentals (DE) · Fundamentals (EN)

Created by Justin Szczepaniak · GitHub Project · LinkedIn

ProPrompt for Developers

Table of Contents

1 Getting Started – Your First Code Prompt

Difficulty: ⭐ Easy

Example – Generating a Simple Function

Copilot Chat – Slash Commands

Context Variables in Chat

2 Writing & Refactoring Code

Difficulty: ⭐⭐ Medium

Example – Refactoring with Clear Constraints

Example – API Endpoint with Full Context

Visualization – Clean Architecture

3 Debugging & Code Review

Difficulty: ⭐⭐ Medium

Example – Systematic Debugging

Example – Code Review Prompt

Debugging Flowchart

4 Advanced – Architecture & Complex Features

Difficulty: ⭐⭐⭐ Hard

Example – System Design with AI

Example – Dockerfile with Multi-Stage Build

5 Agent: Autonomous Development in Agent Mode

Difficulty: ⭐⭐⭐ Hard

What Can Agent Mode Do?

When Agent vs. Chat?

Example – Agent Prompt: New Feature

Agent Mode Best Practices

6 Cheat Sheet for Developers

Quick Prompt Templates

Maximizing Copilot Context

Context Checklist for Code Prompts