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dart_cloud_function

Minimal foundation for serverless HTTP functions in Dart. Extend CloudDartFunction, implement handle(), and deploy.

Note: This package is still in development and subject to change. Not Fully opensource we will make opensource when our early access platform become available

Install

dependencies:
  dart_cloud_function: ^0.1.0

import 'package:dart_cloud_function/dart_cloud_function.dart';

Quick Start

import 'package:dart_cloud_function/dart_cloud_function.dart';

@cloudFunction
class EchoFunction extends CloudDartFunction {
  @override
  Future<CloudResponse> handle({
    required CloudRequest request,
    Map<String, String>? env,
  }) async {
    return CloudResponse.json({
      'method': request.method,
      'path': request.path,
      'query': request.query,
      'body': request.body,
    });
  }
}

Required Structure

When deploying with dart_cloud_cli, your function must follow these rules:

✓ Exactly One CloudDartFunction Class

Your main.dart must contain exactly one class extending CloudDartFunction.

✓ @cloudFunction Annotation

The class must be annotated with @cloudFunction.

✓ No main() Function

Do not include a main() function. The platform handles invocation.

Example - Valid ✅

@cloudFunction
class MyFunction extends CloudDartFunction {
  @override
  Future<CloudResponse> handle({
    required CloudRequest request,
    Map<String, String>? env,
  }) async {
    return CloudResponse.json({'message': 'Hello'});
  }
}

Example - Invalid ❌

// Missing @cloudFunction annotation
class MyFunction extends CloudDartFunction { ... }

// Multiple classes not allowed
@cloudFunction
class Function1 extends CloudDartFunction { ... }
@cloudFunction
class Function2 extends CloudDartFunction { ... }

// main() not allowed
void main() { }

API Reference

• CloudDartFunction (abstract)
  • Future<CloudResponse> handle({required CloudRequest request, Map<String, String>? env})
• CloudRequest
  • String method
  • String path
  • Map<String, String> headers
  • Map<String, String> query
  • dynamic body (JSON-decoded object when content-type: application/json, otherwise String)
  • HttpRequest? raw
• CloudResponse
  • int statusCode
  • Map<String, String> headers
  • dynamic body (String, List<int> for binary, or any JSON-encodable object)
  • Helpers: CloudResponse.json(Object body, {int statusCode, Map<String,String>? headers}), CloudResponse.text(String body, {int statusCode, Map<String,String>? headers})
  • void writeTo(HttpResponse res) to flush the response on a dart:io server.

Request Body Parsing

• CloudRequest is framework-agnostic; construct it from your platform’s incoming request.
• Recommended mapping with dart:io:

  Future<CloudRequest> toCloudRequest(HttpRequest req) async {
    dynamic body;
    if (req.method != 'GET' && req.method != 'HEAD') {
      final bytes = await req.fold<List<int>>(<int>[], (p, e) { p.addAll(e); return p; });
      final mime = req.headers.contentType?.mimeType ?? '';
      if (mime == 'application/json') {
        body = jsonDecode(utf8.decode(bytes));
      } else {
        body = utf8.decode(bytes);
      }
    }
    return CloudRequest(
      method: req.method,
      path: req.uri.path,
      headers: { for (final e in req.headers.entries) e.key: e.value.join(',') },
      query: req.uri.queryParameters,
      body: body,
      raw: req,
    );
  }
  

Error Handling

• Handle errors inside handle and return a CloudResponse with the appropriate status and body.
• Example:

  try {
    // business logic
    return CloudResponse.json({'ok': true});
  } catch (e) {
    return CloudResponse.json({'error': e.toString()}, statusCode: 500);
  }
  

Advanced Usage

• Custom status and headers:

  return CloudResponse(statusCode: 201, headers: {'cache-control': 'no-store'}, body: {'created': true});
  

• Binary responses (e.g., images):

  return CloudResponse(statusCode: 200, headers: {'content-type': 'image/png'}, body: pngBytes);
  

• Basic routing inside handle:

  switch (request.path) {
    case '/health':
      return CloudResponse.text('ok');
    case '/users':
      return CloudResponse.json({'users': []});
    default:
      return CloudResponse.text('not found', statusCode: 404);
  }
  

Testing

• Unit test your function classes by directly invoking handle:

  class TestFn extends CloudDartFunction {
    @override
    Future<CloudResponse> handle(CloudRequest request) async => CloudResponse.text('ok');
  }
  
  final res = await TestFn().handle(CloudRequest(method: 'GET', path: '/', headers: {}, query: {}));
  

• See test/dart_cloud_function_test.dart for an example.

Source Layout

• Public API: lib/dart_cloud_function.dart
• Core implementation: lib/src/dart_cloud_function_base.dart
• Example app: example/dart_cloud_function_example.dart