gnome - how to send email (spawn mail) from gjs gtk app

Question

I am trying to write a gjs app that needs to send emails. The way I have found to do this is using spawn_async_with_pipes() to call mail. The app seems to spawn mail, and I don't get an error, but I don't get any useful output nor do I get the test emails...

I have been at this for a while now and have found little to no useful up to date documentation. I am working with gtk3 and gjs (and glib). I have also tried spawning a shell script that in turn calls mail. This resulted in "could not resolve host" errors and a dead letter queue. So I know that I am spawning my command. I am not concerned about the "could not resolve host command", but by the fact that I can't get it by spawning mail directly.

I am spawning mail like this:

const [res, pid, in_fd, out_fd, err_fd] =
await GLib.spawn_async_with_pipes(null,
                                              ['mail',
                                              '-V',
                                              `-s "${msgObj.subBlock}"`,
                                              `-r ${to}`,
                                              `-S smtp=${HOST}`,
                                              '-S smtp-use-starttls',
                                              '-S smtp-auth=login',
                                              `-S smtp-auth-user=${USER}`,
                                              `-S smtp-auth-password=${PASS}`,
                                              FROM
                                              ], null, GLib.SpawnFlags.SEARCH_PATH, null);

const in_reader = new Gio.DataOutputStream({
        base_stream: new Gio.UnixOutputStream({fd: in_fd})
      });
      var feedRes = in_reader.put_string(msgObj.msgBlock, null);

      const out_reader = new Gio.DataInputStream({
        base_stream: new Gio.UnixInputStream({fd: out_fd})
      });
      const err_reader = new Gio.DataInputStream({
        base_stream: new Gio.UnixInputStream({fd: err_fd})
      });
      var out = out_reader.read_until("", null);
      var err = err_reader.read_until("", null);

      print(` > out : "${out}"`);
      print(` > res : "${res}"`);
      print(` > feedRes : "${feedRes}"`);
      print(` > err : "${err}"`);

err is 0, and res is just true

I don't know what the output should be, but I'm not getting a recognizable error, and no email is being delivered... How can I get my app to send emails? Is spawning mail not the way to go? Thanks in advance for any pointers you can give me.

标签： gnomegjs

Answer 1

我认为这里有几件事让您感到困惑，我想我可以澄清一下。

await GLib.spawn_async_with_pipes(

GLib 有自己的异步函数概念，在适用时需要包装在 Promise 中才能有效地使用await关键字。在这种情况下，GLib.spawn_async_with_pipes()它并不是你想的那样异步，但这没关系，因为我们将使用更高级别的 class Gio.Subprocess。

async function mail(msgObj, to, host, user, pass, cancellable = null) {
    try {
        let proc = new Gio.Subprocess({
            argv: ['mail',
                   '-V',
                   // Option switches and values are separate args
                   '-s', `"${msgObj.subBlock}"`,
                   '-r', `${to}`,
                   '-S', `smtp=${host}`,
                   '-S', 'smtp-use-starttls',
                   '-S', 'smtp-auth=login',
                   '-S', `smtp-auth-user=${user}`,
                   '-S', `smtp-auth-password=${pass}`,
                   FROM
            ],
            flags: Gio.SubprocessFlags.STDIN_PIPE |
                   Gio.SubprocessFlags.STDOUT_PIPE |
                   Gio.SubprocessFlags.STDERR_MERGE
        });
        // Classes that implement GInitable must be initialized before use, but
        // you could use Gio.Subprocess.new(argv, flags) which will call this for you
        proc.init(cancellable);

        // We're going to wrap a GLib async function in a Promise so we can
        // use it like a native JavaScript async function.
        //
        // You could alternatively return this Promise instead of awaiting it
        // here, but that's up to you.
        let stdout = await new Promise((resolve, reject) => {

            // communicate_utf8() returns a string, communicate() returns a
            // a GLib.Bytes and there are "headless" functions available as well
            proc.communicate_utf8_async(
                // This is your stdin, which can just be a JS string
                msgObj.msgBlock,

                // we've been passing this around from the function args; you can
                // create a Gio.Cancellable and call `cancellable.cancel()` to
                // stop the command or any other operation you've passed it to at
                // any time, which will throw an "Operation Cancelled" error.
                cancellable,

                // This is the GAsyncReady callback, which works like any other
                // callback, but we need to ensure we catch errors so we can
                // propagate them with `reject()` to make the Promise work
                // properly
                (proc, res) => {
                    try {
                        let [ok, stdout, stderr] = proc.communicate_utf8_finish(res);
                        // Because we used the STDERR_MERGE flag stderr will be
                        // included in stdout. Obviously you could also call
                        // `resolve([stdout, stderr])` if you wanted to keep both
                        // and separate them.
                        // 
                        // This won't affect whether the proc actually return non-
                        // zero causing the Promise to reject()
                        resolve(stdout);
                    } catch (e) {
                        reject(e);
                    }
                }
            );
        });

        return stdout;
    } catch (e) {
        // This could be any number of errors, but probably it will be a GError
        // in which case it will have `code` property carrying a GIOErrorEnum
        // you could use to programmatically respond to, if desired.
        logError(e);
    }
}

Gio.Subprocess总的来说是一个更好的选择，但特别是对于不能将“输出”参数传递给函数的语言绑定。使用GLib.spawn_async_with_pipes你通常会通过NULL来防止打开任何你不想要的管道，并始终确保你关闭任何你不想要的管道。由于我们在 GJS 中无法做到这一点，因此您最终会得到无法关闭的悬空文件描述符。

Gio.Subprocess为您做了很多工作并确保文件描述符正在关闭，防止僵尸进程，为您设置子监视以及您真正不想担心的其他事情。它还具有获取 IO 流的便利功能，因此您不必自己包装 fd 以及其他有用的东西。

我写了一篇较长的 GJS 异步编程入门书，您可能会在此处找到帮助。尽管它很快你应该能够轻而易举，它试图消除一些关于 GLib 异步、JavaScript 异步和 GLib 主循环与 JS 事件循环之间关系的混淆。