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* Plz: (plz). HTTP library using Curl as a backend.
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plz.el
******
file:http://elpa.gnu.org/packages/plz.svg
(http://elpa.gnu.org/packages/plz.html)
‘plz’ is an HTTP library for Emacs. It uses ‘curl’ as a backend,
which avoids some of the issues with using Emacs’s built-in ‘url’
library. It supports both synchronous and asynchronous requests. Its
API is intended to be simple, natural, and expressive. Its code is
intended to be simple and well-organized. Every feature is tested
against httpbin (https://httpbin.org/).
* Menu:
* Installation::
* Usage::
* Changelog::
* Credits::
* Development::
* License::
— The Detailed Node Listing —
Installation
* GNU ELPA::
* Manual::
Usage
* Examples::
* Functions::
* Queueing::
* Tips::
Changelog
* 0.7: 07.
* 0.6: 06.
* 0.5.4: 054.
* 0.5.3: 053.
* 0.5.2: 052.
* 0.5.1: 051.
* 0.5: 05.
* 0.4: 04.
* 0.3: 03.
* 0.2.1: 021.
* 0.2: 02.
* 0.1: 01.
Development
* Copyright assignment::
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1 Installation
**************
* Menu:
* GNU ELPA::
* Manual::
File: README.info, Node: GNU ELPA, Next: Manual, Up: Installation
1.1 GNU ELPA
============
‘plz’ is available in GNU ELPA (http://elpa.gnu.org/packages/plz.html).
It may be installed in Emacs using the ‘package-install’ command.
File: README.info, Node: Manual, Prev: GNU ELPA, Up: Installation
1.2 Manual
==========
‘plz’ has no dependencies other than Emacs and ‘curl’. It’s known to
work on Emacs 26.3 or later. To install it manually, simply place
‘plz.el’ in your ‘load-path’ and ‘(require 'plz)’.
File: README.info, Node: Usage, Next: Changelog, Prev: Installation, Up: Top
2 Usage
*******
The main public function is ‘plz’, which sends an HTTP request and
returns either the result of the specified type (for a synchronous
request), or the ‘curl’ process object (for asynchronous requests). For
asynchronous requests, callback, error-handling, and finalizer functions
may be specified, as well as various other options.
* Menu:
* Examples::
* Functions::
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File: README.info, Node: Examples, Next: Functions, Up: Usage
2.1 Examples
============
Synchronously ‘GET’ a URL and return the response body as a decoded
string (here, raw JSON):
(plz 'get "https://httpbin.org/user-agent")
"{\n \"user-agent\": \"curl/7.35.0\"\n}\n"
Synchronously ‘GET’ a URL that returns a JSON object, and parse and
return it as an alist:
(plz 'get "https://httpbin.org/get" :as #'json-read)
((args)
(headers
(Accept . "*/*")
(Accept-Encoding . "deflate, gzip")
(Host . "httpbin.org")
(User-Agent . "curl/7.35.0"))
(url . "https://httpbin.org/get"))
Asynchronously ‘POST’ a JSON object in the request body, then parse a
JSON object from the response body, and call a function with the result:
(plz 'post "https://httpbin.org/post"
:headers '(("Content-Type" . "application/json"))
:body (json-encode '(("key" . "value")))
:as #'json-read
:then (lambda (alist)
(message "Result: %s" (alist-get 'data alist))))
Result: {"key":"value"}
Synchronously download a JPEG file, then create an Emacs image object
from the data:
(let ((jpeg-data (plz 'get "https://httpbin.org/image/jpeg" :as 'binary)))
(create-image jpeg-data nil 'data))
(image :type jpeg :data ""ÿØÿà^@^PJFIF...")
File: README.info, Node: Functions, Next: Queueing, Prev: Examples, Up: Usage
2.2 Functions
=============
‘plz’
_(method url &key headers body else finally noquery (as ’string)
(then ’sync) (body-type ’text) (decode t decode-s) (connect-timeout
plz-connect-timeout) (timeout plz-timeout))_
Request ‘METHOD’ from ‘URL’ with curl. Return the curl process
object or, for a synchronous request, the selected result.
‘HEADERS’ may be an alist of extra headers to send with the
request.
‘BODY’ may be a string, a buffer, or a list like ‘(file FILENAME)’
to upload a file from disk.
‘BODY-TYPE’ may be ‘text’ to send ‘BODY’ as text, or ‘binary’ to
send it as binary.
‘AS’ selects the kind of result to pass to the callback function
‘THEN’, or the kind of result to return for synchronous requests.
It may be:
• ‘buffer’ to pass the response buffer, which will be narrowed
to the response body and decoded according to ‘DECODE’.
• ‘binary’ to pass the response body as an un-decoded string.
• ‘string’ to pass the response body as a decoded string.
• ‘response’ to pass a ‘plz-response’ structure.
• ‘file’ to pass a temporary filename to which the response body
has been saved without decoding.
• ‘(file ~FILENAME)’ to pass ‘FILENAME’ after having saved the
response body to it without decoding. ‘FILENAME’ must be a
non-existent file; if it exists, it will not be overwritten,
and an error will be signaled.
• A function, which is called in the response buffer with it
narrowed to the response body (suitable for, e.g.
‘json-read’).
If ‘DECODE’ is non-nil, the response body is decoded automatically.
For binary content, it should be nil. When ‘AS’ is ‘binary’,
‘DECODE’ is automatically set to nil.
‘THEN’ is a callback function, whose sole argument is selected
above with ‘AS’; if the request fails and no ‘ELSE’ function is
given (see below), the argument will be a ‘plz-error’ structure
describing the error. Or ‘THEN’ may be ‘sync’ to make a
synchronous request, in which case the result is returned directly
from this function.
‘ELSE’ is an optional callback function called when the request
fails (i.e. if curl fails, or if the ‘HTTP’ response has a non-2xx
status code). It is called with one argument, a ‘plz-error’
structure. If ‘ELSE’ is nil, a ‘plz-curl-error’ or
‘plz-http-error’ is signaled when the request fails, with a
‘plz-error’ structure as the error data. For synchronous requests,
this argument is ignored.
‘NOTE’: In v0.8 of ‘plz’, only one error will be signaled:
‘plz-error’. The existing errors, ‘plz-curl-error’ and
‘plz-http-error’, inherit from ‘plz-error’ to allow applications to
update their code while using v0.7 (i.e. any ‘condition-case’
forms should now handle only ‘plz-error’, not the other two).
‘FINALLY’ is an optional function called without argument after
‘THEN’ or ‘ELSE’, as appropriate. For synchronous requests, this
argument is ignored.
‘CONNECT-TIMEOUT’ and ‘TIMEOUT’ are a number of seconds that limit
how long it takes to connect to a host and to receive a response
from a host, respectively.
‘NOQUERY’ is passed to ‘make-process’, which see.
File: README.info, Node: Queueing, Next: Tips, Prev: Functions, Up: Usage
2.3 Queueing
============
‘plz’ provides a simple system for queueing HTTP requests. First, make
a ‘plz-queue’ struct by calling ‘make-plz-queue’. Then call ‘plz-queue’
with the struct as the first argument, and the rest of the arguments
being the same as those passed to ‘plz’. Then call ‘plz-run’ to run the
queued requests.
All of the queue-related functions return the queue as their value,
making them easy to use. For example:
(defvar my-queue (make-plz-queue :limit 2))
(plz-run
(plz-queue my-queue
'get "https://httpbin.org/get?foo=0"
:then (lambda (body) (message "%s" body))))
Or:
(let ((queue (make-plz-queue :limit 2
:finally (lambda ()
(message "Queue empty."))))
(urls '("https://httpbin.org/get?foo=0"
"https://httpbin.org/get?foo=1")))
(plz-run
(dolist (url urls queue)
(plz-queue queue 'get url
:then (lambda (body) (message "%s" body))))))
You may also clear a queue with ‘plz-clear’, which cancels any active
or queued requests and calls their ‘:else’ functions. And ‘plz-length’
returns the number of a queue’s active and queued requests.
File: README.info, Node: Tips, Prev: Queueing, Up: Usage
2.4 Tips
========
• You can customize settings in the ‘plz’ group, but this can only be
used to adjust a few defaults. It’s not intended that changing or
binding global variables be necessary for normal operation.
File: README.info, Node: Changelog, Next: Credits, Prev: Usage, Up: Top
3 Changelog
***********
* Menu:
* 0.7: 07.
* 0.6: 06.
* 0.5.4: 054.
* 0.5.3: 053.
* 0.5.2: 052.
* 0.5.1: 051.
* 0.5: 05.
* 0.4: 04.
* 0.3: 03.
* 0.2.1: 021.
* 0.2: 02.
* 0.1: 01.
File: README.info, Node: 07, Next: 06, Up: Changelog
3.1 0.7
=======
*Changes*
• A new error signal, ‘plz-error’, is defined. The existing signals,
‘plz-curl-error’ and ‘plz-http-error’, inherit from it, so handling
‘plz-error’ catches both.
*NOTE:* The existing signals, ‘plz-curl-error’ and
‘plz-http-error’, are hereby deprecated, and they will be removed
in v0.8. Applications should be updated while using v0.7 to only
expect ‘plz-error’.
*Fixes*
• Significant improvement in reliability by implementing failsafes
and workarounds for Emacs’s process-handling code. (See #3
(https://github.com/alphapapa/plz.el/issues/3).)
• STDERR output from curl processes is not included in response
bodies (which sometimes happened, depending on Emacs’s internal
race conditions). (Fixes #23
(https://github.com/alphapapa/plz.el/issues/23).)
• Use ‘with-local-quit’ for synchronous requests (preventing Emacs
from complaining sometimes). (Fixes #26
(https://github.com/alphapapa/plz.el/issues/26).)
• Various fixes for ‘:as 'buffer’ result type: decode body when
appropriate; unset multibyte for binary; narrow to body; don’t kill
buffer prematurely.
• When clearing a queue, don’t try to kill finished processes.
*Internal*
• Response processing now happens outside the process sentinel, so
any errors (e.g. in user callbacks) are not signaled from inside
the sentinel. (This avoids the 2-second pause Emacs imposes in
such cases.)
• Tests run against a local instance of httpbin
(https://github.com/postmanlabs/httpbin) (since the ‘httpbin.org’
server is often overloaded).
• No buffer-local variables are defined anymore; process properties
are used instead.
File: README.info, Node: 06, Next: 054, Prev: 07, Up: Changelog
3.2 0.6
=======
*Additions*
• Function ‘plz’’s ‘:body’ argument now accepts a list like ‘(file
FILENAME)’ to upload a file from disk (by passing the filename to
curl, rather than reading its content into Emacs and sending it to
curl through the pipe).
*Fixes*
• Function ‘plz’’s docstring now mentions that the ‘:body’ argument
may also be a buffer (an intentional feature that was accidentally
undocumented).
• Handle HTTP 3xx redirects when using ‘:as 'response’.
File: README.info, Node: 054, Next: 053, Prev: 06, Up: Changelog
3.3 0.5.4
=========
*Fixes*
• Only run queue’s ‘finally’ function after queue is empty. (New
features should not be designed and released on a Friday.)
File: README.info, Node: 053, Next: 052, Prev: 054, Up: Changelog
3.4 0.5.3
=========
*Fixes*
• Move new slot in ‘plz-queue’ struct to end to prevent invalid
byte-compiler expansions for already-compiled applications (which
would require them to be recompiled after upgrading ‘plz’).
File: README.info, Node: 052, Next: 051, Prev: 053, Up: Changelog
3.5 0.5.2
=========
*Fixes*
• When clearing a queue, only call ‘plz-queue’’s ‘finally’ function
when specified.
File: README.info, Node: 051, Next: 05, Prev: 052, Up: Changelog
3.6 0.5.1
=========
*Fixes*
• Only call ‘plz-queue’’s ‘finally’ function when specified. (Thanks
to Dan Oriani (https://github.com/redchops) for reporting.)
File: README.info, Node: 05, Next: 04, Prev: 051, Up: Changelog
3.7 0.5
=======
*Additions*
• Struct ‘plz-queue’’s ‘finally’ slot, a function called when the
queue is finished.
File: README.info, Node: 04, Next: 03, Prev: 05, Up: Changelog
3.8 0.4
=======
*Additions*
• Support for HTTP ‘HEAD’ requests. (Thanks to Inc. for
sponsoring.)
*Changes*
• Allow sending ‘POST’ and ‘PUT’ requests without bodies. (#16
(https://github.com/alphapapa/plz.el/issues/16). Thanks to Joseph
Turner (https://github.com/josephmturner) for reporting. Thanks to
Inc. for sponsoring.)
*Fixes*
• All 2xx HTTP status codes are considered successful. (#17
(https://github.com/alphapapa/plz.el/issues/17). Thanks to Joseph
Turner (https://github.com/josephmturner) for reporting. Thanks to
Inc. for sponsoring.)
• Errors are signaled with error data correctly.
*Internal*
• Test suite explicitly tests with both HTTP/1.1 and HTTP/2.
• Test suite also tests with Emacs versions 27.2, 28.1, and 28.2.
File: README.info, Node: 03, Next: 021, Prev: 04, Up: Changelog
3.9 0.3
=======
*Additions*
• Handle HTTP proxy headers from Curl. (#2
(https://github.com/alphapapa/plz.el/issues/2). Thanks to Alan
Third (https://github.com/alanthird) and Sawyer Zheng
(https://github.com/sawyerzheng) for reporting.)
*Fixes*
• Replaced words not in Ispell’s default dictionaries (so ‘checkdoc’
linting succeeds).
File: README.info, Node: 021, Next: 02, Prev: 03, Up: Changelog
3.10 0.2.1
==========
*Fixes*
• Handle when Curl process is interrupted.
File: README.info, Node: 02, Next: 01, Prev: 021, Up: Changelog
3.11 0.2
========
*Added*
• Simple request queueing.
File: README.info, Node: 01, Prev: 02, Up: Changelog
3.12 0.1
========
Initial release.
File: README.info, Node: Credits, Next: Development, Prev: Changelog, Up: Top
4 Credits
*********
• Thanks to Chris Wellons (https://github.com/skeeto), author of the
Elfeed (https://github.com/skeeto/elfeed) feed reader and the
popular blog null program (https://nullprogram.com/), for his
invaluable advice, review, and encouragement.
File: README.info, Node: Development, Next: License, Prev: Credits, Up: Top
5 Development
*************
Bug reports, feature requests, suggestions — _oh my_!
Note that ‘plz’ is a young library, and its only client so far is
Ement.el (https://github.com/alphapapa/ement.el). There are a variety
of HTTP and ‘curl’ features it does not yet support, since they have not
been needed by the author. Patches are welcome, as long as they include
passing tests.
* Menu:
* Copyright assignment::
File: README.info, Node: Copyright assignment, Up: Development
5.1 Copyright assignment
========================
This package is part of GNU Emacs (https://www.gnu.org/software/emacs/),
being distributed in GNU ELPA (https://elpa.gnu.org/). Contributions to
this project must follow GNU guidelines, which means that, as with other
parts of Emacs, patches of more than a few lines must be accompanied by
having assigned copyright for the contribution to the FSF. Contributors
who wish to do so may contact emacs-devel@gnu.org <emacs-devel@gnu.org>
to request the assignment form.
File: README.info, Node: License, Prev: Development, Up: Top
6 License
*********
GPLv3
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