Makefile

define PROXY_FN
export async function onRequest(context) {
	const { request, params, env } = context;
	const url = new URL(request.url);
	url.host = env.API_HOST;
	url.pathname = params.path.join('') === 'json' ? `/api/json` : params.path.join('/');
	if (request.method === 'POST' && !request.headers.get('Content-Type')) {
		const headers = Object.fromEntries(request.headers.entries())
		return fetch(url, {
			method: request.method,
			headers: {
				...headers,
				'Content-Type': 'application/json'
			},
			body: '{}'
		});
	}
	return fetch(url, request);
}
endef

export PROXY_FN

build:
	mkdir -p functions/api
	echo $$PROXY_FN >> functions/api/[[path]].js
	npm run build

clean:
	rm -rf dist functions

.PHONY: build clean

Rakefile

PROXY_FN = <<-JS
export async function onRequest(context) {
  const { request, params, env } = context;
  const url = new URL(request.url);
  url.host = env.API_HOST;
  url.pathname = params.path.join('') === 'json' ? `/api/json` : params.path.join('/');
  if (request.method === 'POST' && !request.headers.get('Content-Type')) {
    const headers = Object.fromEntries(request.headers.entries())
    return fetch(url, {
      method: request.method,
      headers: {
        ...headers,
        'Content-Type': 'application/json'
      },
      body: '{}'
    });
  }
  return fetch(url, request);
}
JS

task :default do
  FileUtils.makedirs 'functions/api'
  File.write 'functions/api/[[path]].js', PROXY_FN
  sh 'npm run build'
end