[neomutt-users] Neomutt: now featuring Lua scripting!
z+mutt+neomutt at m0g.net
Fri Apr 28 00:49:40 CEST 2017
My dear neomutters,
Following a few past mails on the topic, now neomutt is embedding a Lua
runtime that makes it possible to access all of neomutt's 'public' API
as a Lua API.
Because the Muttrc language is just a simple descriptive language (it
being a list of command statements), it is not aimed at being a Turing
complete language — pardon my French. But thanks to Lua, you can get it
all with a fully feature language that's built-in, and does not add
weight to the Neomutt binary.
Because up until now I've been the only user of Lua in Neomutt, please,
please, try it out, implement some fresh ideas, have fun with it!
But don't hesitate to torture it, find edge cases, make it scream,
crash, burn 🔥! And don't forget to report if you do!
When the Lua abilities (and its API) will be considered stable enough by
the community, it will be enabled by default at compilation, and
properly documented in the manual.
# Presentation of the Lua API
There are three main novelties with this feature:
1. there is two new Neomuttrc commands:
:lua to execute a single line of lua
:lua-source to execute a lua source file
the Lua interpreter is running for the whole duration of the Neomutt
session. So a variable declared in Neomuttrc will be available in a
sourced Lua file, and during runtime with :lua.
2. a command line argument --batch (-B) that starts mutt, executes any
Neomuttrc file commands and exists without launching the GUI or
expecting any mail composition.
That can be useful if you want to run a Lua script exploiting the Neomutt
API, but without launching the ncurses user interface.
3. the interpreter exposes in Lua's global scope a mutt namespace
containing a very basic API.
⚠️ Because Lua support is still very immature, you need to explicitely
enable it at compile time, by adding the `--enable-lua` option to the
# Description of the API
mutt.get(option) returns an option into a object
mutt.set(option, value) sets options to value
settings are typed accordingly to Neomutt's expectations with matching
Lua types. If you feed it an incompatible type, expect an exception!
mutt.enter(cmd) runs a string containing a command exactly
as you'd write it on the `:` enter-command
mutt.call(cmd, arg1, …) runs a command, the command name is the
first argument, its arguments all the
mutt.command.<cmd>(args) runs a command as a standard Lua function.
Some commands can return values, and those will be assignable.
Upon error, they will throw exceptions.
which can be used as a muttrc:
lua mutt.set("visual", "less")
lua mutt.set("arrow_cursor", true)
lua mutt.set("abort_noattach", mutt.QUAD_ASKNO)
# commands, the three following ones are strictly equivalent
lua mutt.command.color("quoted", "brightblue", "default")
lua mutt.call("color", "quoted", "brightblue", "default")
lua mutt.enter("color quoted brightblue default")
# of course the first one is more elegant
# Road ahead
I'm making a call for everybody interested to try it out, integrate it
in their configurations, and implement neat ideas! With that simple API,
and the full force of Lua libraries, it's possible to create a lot of
For the next step, I'd like to follow up with:
* binding all the commands that are contextualized to the buffers (index,
* exposing internals, using functions and objects:
* manipulate the index,
* manipulate the pager,
* maniputale a message details,
* manipulate a message's attachments
* and so and sofort
eventually, I think that some mutt patches that became part of Neomutt
could be extracted as Lua plugins, or some unpopular feature requests
could be made using it.
* a test suite has been implemented as an example and is available in
the sources (you'll need to install `busted` with luarocks to test it):
* here's the ticket that has been used to track development of that
* here's a script I used to check typing of the get/set options during
development (a poor man's unit test):
don't hesitate to follow up on this mail, ping me on IRC (zmo on
#neomutt), open an issue in the bugtracker for ideas, feature requests,
or when you'll find a bug.
Thank you for reading this mail 🙌
And have fun with it!
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