From cURL to Code: Automating Developer Onboarding

The Universal Language of APIs

cURL is the lingua franca of API communication. Every developer knows it, every API supports it, and it captures everything needed to make a request:

curl -X POST https://api.example.com/v1/users \
  -H "Authorization: Bearer sk_test_123" \
  -H "Content-Type: application/json" \
  -d '{"email": "dev@example.com", "name": "Test User"}'

But here's the thing: nobody actually uses cURL in production. They use Python, JavaScript, Go, or a dozen other languages.

Building a cURL Parser

The first step is parsing cURL commands into a structured format:

interface ParsedRequest {
  method: string;
  url: string;
  headers: Record<string, string>;
  body?: any;
  auth?: {
    type: 'bearer' | 'basic' | 'api-key';
    credentials: string;
  };
}

Handling Common cURL Flags

Edge Cases to Handle

Code Generation Strategies

Template-Based Generation

The simplest approach: maintain templates for each language and fill in values.

Python template:

import requests

response = requests.{{method}}(
    "{{url}}",
    headers={{headers}},
    {{#if body}}json={{body}}{{/if}}
)
print(response.json())

Pros: Easy to maintain, predictable output

Cons: Limited flexibility, templates proliferate

AST-Based Generation

Build an abstract syntax tree and render to each language:

const ast = {
  type: 'http_request',
  method: 'POST',
  url: 'https://api.example.com/v1/users',
  headers: [...],
  body: {...}
};

const pythonCode = renderPython(ast);
const jsCode = renderJavaScript(ast);

Pros: Consistent logic, easier testing

Cons: More complex to implement

Language-Specific Considerations

Python

JavaScript/Node.js

Go

Ruby

Making Generated Code Production-Ready

Basic generated code gets developers started, but production code needs more:

1. Error Handling

try:
    response = requests.post(url, json=data, headers=headers)
    response.raise_for_status()
    return response.json()
except requests.exceptions.HTTPError as e:
    print(f"HTTP error: {e.response.status_code}")
except requests.exceptions.RequestException as e:
    print(f"Request failed: {e}")

2. Retry Logic

from tenacity import retry, stop_after_attempt, wait_exponential

@retry(stop=stop_after_attempt(3), wait=wait_exponential())
def make_api_call():
    ...

3. Environment Variables

import os

API_KEY = os.environ.get('API_KEY')
headers = {'Authorization': f'Bearer {API_KEY}'}

Building the Full System

A complete cURL-to-code system includes:

Testing Your Generator

Create a comprehensive test suite:

const testCases = [
  { name: 'GET request', curl: 'curl https://api.example.com' },
  { name: 'POST with JSON', curl: 'curl -X POST -d '{"key":"value"}' ...' },
  { name: 'Auth header', curl: 'curl -H "Authorization: Bearer token" ...' },
  // ... 50+ cases covering edge cases
];

testCases.forEach(({ name, curl }) => {
  const parsed = parseCurl(curl);
  LANGUAGES.forEach(lang => {
    const code = generate(parsed, lang);
    expect(code).toMatchSnapshot(`${name}-${lang}`);
  });
});

Real-World Impact

Companies using automated cURL-to-code report:

The investment in building a robust converter pays dividends across your entire developer experience.