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https://github.com/chuntaro/emacs-async-await
Async/Await for Emacs
https://github.com/chuntaro/emacs-async-await
async await emacs promise
Last synced: 4 months ago
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Async/Await for Emacs
- Host: GitHub
- URL: https://github.com/chuntaro/emacs-async-await
- Owner: chuntaro
- Created: 2017-02-02T11:07:31.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2022-08-27T04:37:50.000Z (over 2 years ago)
- Last Synced: 2024-09-29T18:01:27.400Z (4 months ago)
- Topics: async, await, emacs, promise
- Language: Emacs Lisp
- Homepage:
- Size: 23.4 KB
- Stars: 72
- Watchers: 5
- Forks: 5
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
Async/Await for Emacs
=====================
This is a simple implementation of Async/Await.
Inspired by the Async/Await implementation of TypeScript.
This implementation uses generator.el included in Emacs 25 and [promise.el](https://github.com/chuntaro/emacs-promise).
For detailed tutorials on its use, see [What about Async/Await?](https://devblogs.microsoft.com/typescript/what-about-async-await/) (TypeScript)
Installation
------------
You can install from MELPA using package.el.
The package name is **async-await**.
Usage
-----
See [async-await-examples.el](https://github.com/chuntaro/emacs-async-await/blob/master/examples/async-await-examples.el) for details.
```emacs-lisp
(require 'async-await)
(defun wait-async (n)
(promise-new (lambda (resolve _reject)
(run-at-time n
nil
(lambda ()
(funcall resolve n))))))
(async-defun example2 ()
(print (await (wait-async 0.5)))
(message "---")
(print (await (wait-async 1.0)))
(message "---")
(print (await (wait-async 1.5)))
(message "---")
(message "await done"))
(example2) =>
0.5
---
1.0
---
1.5
---
await done
The result of the execution is outputted from the top to the bottom
like the order written in the code. However, asynchronously!
```
An example using `url-retrieve 'as a more complicated example.
```emacs-lisp
(require 'async-await)
(require 'url-http)
(require 'xml)
(require 'dom)
(defun xml-retrieve (url)
"Return `Promise' to resolve with XML object obtained by HTTP request."
(promise-new
(lambda (resolve reject)
(url-retrieve url
(lambda (status)
;; All errors are reliably captured and rejected with appropriate values.
(if (plist-get status :error)
(funcall reject (plist-get status :error))
(condition-case ex
(with-current-buffer (current-buffer)
(if (not (url-http-parse-headers))
(funcall reject (buffer-string))
(search-forward-regexp "\n\\s-*\n" nil t)
(funcall resolve (xml-parse-region))))
(error (funcall reject ex)))))))))
(defun get-text-first-tag (xml tag)
"Returns the first text that matches TAG in XML."
(decode-coding-string (dom-text (cl-first (dom-by-tag xml tag)))
'utf-8))
(defun get-short-text-first-tag (xml tag)
"Truncate the text obtained with `get-text-first-tag'."
(concat (truncate-string-to-width (get-text-first-tag xml tag) 64)
" ..."))
(defun wait-seconds (seconds fn &rest args)
"Return `Promise' to execute the function after the specified time."
(promise-new (lambda (resolve _reject)
(run-at-time seconds
nil
(lambda ()
(funcall resolve (apply fn args)))))))
(async-defun example8 ()
"Example using `xml-retrieve'."
(condition-case reason
(let* ((wikipedia-url (concat "https://en.wikipedia.org/w/api.php"
"?format=xml&action=query&prop=extracts"
"&exintro=&explaintext=&titles="))
(xml-gnu (await (xml-retrieve (concat wikipedia-url "GNU"))))
;; Request after 2 seconds for load reduction.
(xml-emacs (await (wait-seconds 2
#'xml-retrieve
(concat wikipedia-url "Emacs")))))
(print (get-short-text-first-tag xml-gnu 'extract))
(print (get-short-text-first-tag xml-emacs 'extract)))
(error (message "error: %s" reason))))
```