Translate a KeyedTraversable of Awaitables into a single Awaitable ofMap`

namespace HH\Asio;

function m<Tk as arraykey, Tv>(
  KeyedTraversable<Tk, Awaitable<Tv>> $awaitables,
): Awaitable<Map<Tk, Tv>>;

This function takes any KeyedTraversable object of Awaitables (i.e., each member of the KeyedTraversable has a value of type of Awaitable, likely from a call to a function that returned Awaitable<T>), and transforms those Awaitables into one big Awaitable Map.

This function is called m because we are returning a map of Awaitable.

Only When you await or join the resulting Awaitable, will all of the key/values in the Map within the returned Awaitable be available.




 * Query an arbitrary number of URLs in parallel
 * returning them as a Map of string responses.
async function get_urls(
  \ConstMap<string, string> $urls,
): Awaitable<Map<string, string>> {
  // Wrap each URL string into a curl_exec awaitable
  $handles = $urls->map($url ==> \HH\Asio\curl_exec($url));

  // Wait on each handle in parallel and return the results
  return await \HH\Asio\m($handles);

$urls = ImmMap {
  'com' => "http://example.com",
  'net' => "http://example.net",
  'org' => "http://example.org",

$pages = \HH\Asio\join(get_urls($urls));
foreach ($pages as $name => $page) {
  echo $name.': ';
  echo substr($page, 0, 15).' ... '.substr($page, -8);
com: <!doctype html> ... </html>
net: <!doctype html> ... </html>
org: <!doctype html> ... </html>