neovim/runtime/doc/if_lua.txt

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*if_lua.txt* Nvim
NVIM REFERENCE MANUAL
Lua engine *lua* *Lua*
Type |gO| to see the table of contents.
==============================================================================
Introduction *lua-intro*
The Lua 5.1 language is builtin and always available. Try this command to get
an idea of what lurks beneath: >
:lua print(vim.inspect(package.loaded))
Nvim includes a "standard library" |lua-stdlib| for Lua. It complements the
"editor stdlib" (|functions| and Ex commands) and the |API|, all of which can
be used from Lua code.
Module conflicts are resolved by "last wins". For example if both of these
are on 'runtimepath':
runtime/lua/foo.lua
~/.config/nvim/lua/foo.lua
then `require('foo')` loads "~/.config/nvim/lua/foo.lua", and
"runtime/lua/foo.lua" is not used. See |lua-require| to understand how Nvim
finds and loads Lua modules. The conventions are similar to VimL plugins,
with some extra features. See |lua-require-example| for a walkthrough.
==============================================================================
Importing Lua modules *lua-require*
Nvim automatically adjusts `package.path` and `package.cpath` according to
effective 'runtimepath' value. Adjustment happens whenever 'runtimepath' is
changed. `package.path` is adjusted by simply appending `/lua/?.lua` and
`/lua/?/init.lua` to each directory from 'runtimepath' (`/` is actually the
first character of `package.config`).
Similarly to `package.path`, modified directories from 'runtimepath' are also
added to `package.cpath`. In this case, instead of appending `/lua/?.lua` and
`/lua/?/init.lua` to each runtimepath, all unique `?`-containing suffixes of
the existing `package.cpath` are used. Example:
1. Given that
- 'runtimepath' contains `/foo/bar,/xxx;yyy/baz,/abc`;
- initial (defined at compile-time or derived from
`$LUA_CPATH`/`$LUA_INIT`) `package.cpath` contains
`./?.so;/def/ghi/a?d/j/g.elf;/def/?.so`.
2. It finds `?`-containing suffixes `/?.so`, `/a?d/j/g.elf` and `/?.so`, in
order: parts of the path starting from the first path component containing
question mark and preceding path separator.
3. The suffix of `/def/?.so`, namely `/?.so` is not unique, as its the same
as the suffix of the first path from `package.path` (i.e. `./?.so`). Which
leaves `/?.so` and `/a?d/j/g.elf`, in this order.
4. 'runtimepath' has three paths: `/foo/bar`, `/xxx;yyy/baz` and `/abc`. The
second one contains semicolon which is a paths separator so it is out,
leaving only `/foo/bar` and `/abc`, in order.
5. The cartesian product of paths from 4. and suffixes from 3. is taken,
giving four variants. In each variant `/lua` path segment is inserted
between path and suffix, leaving
- `/foo/bar/lua/?.so`
- `/foo/bar/lua/a?d/j/g.elf`
- `/abc/lua/?.so`
- `/abc/lua/a?d/j/g.elf`
6. New paths are prepended to the original `package.cpath`.
The result will look like this:
`/foo/bar,/xxx;yyy/baz,/abc` ('runtimepath')
× `./?.so;/def/ghi/a?d/j/g.elf;/def/?.so` (`package.cpath`)
= `/foo/bar/lua/?.so;/foo/bar/lua/a?d/j/g.elf;/abc/lua/?.so;/abc/lua/a?d/j/g.elf;./?.so;/def/ghi/a?d/j/g.elf;/def/?.so`
Note:
- To track 'runtimepath' updates, paths added at previous update are
remembered and removed at the next update, while all paths derived from the
new 'runtimepath' are prepended as described above. This allows removing
paths when path is removed from 'runtimepath', adding paths when they are
added and reordering `package.path`/`package.cpath` content if 'runtimepath'
was reordered.
- Although adjustments happen automatically, Nvim does not track current
values of `package.path` or `package.cpath`. If you happen to delete some
paths from there you can set 'runtimepath' to trigger an update: >
let &runtimepath = &runtimepath
- Skipping paths from 'runtimepath' which contain semicolons applies both to
`package.path` and `package.cpath`. Given that there are some badly written
plugins using shell which will not work with paths containing semicolons it
is better to not have them in 'runtimepath' at all.
------------------------------------------------------------------------------
LUA PLUGIN EXAMPLE *lua-require-example*
The following example plugin adds a command `:MakeCharBlob` which transforms
current buffer into a long `unsigned char` array. Lua contains transformation
function in a module `lua/charblob.lua` which is imported in
`autoload/charblob.vim` (`require("charblob")`). Example plugin is supposed
to be put into any directory from 'runtimepath', e.g. `~/.config/nvim` (in
this case `lua/charblob.lua` means `~/.config/nvim/lua/charblob.lua`).
autoload/charblob.vim: >
function charblob#encode_buffer()
call setline(1, luaeval(
\ 'require("charblob").encode(unpack(_A))',
\ [getline(1, '$'), &textwidth, ' ']))
endfunction
plugin/charblob.vim: >
if exists('g:charblob_loaded')
finish
endif
let g:charblob_loaded = 1
command MakeCharBlob :call charblob#encode_buffer()
lua/charblob.lua: >
local function charblob_bytes_iter(lines)
local init_s = {
next_line_idx = 1,
next_byte_idx = 1,
lines = lines,
}
local function next(s, _)
if lines[s.next_line_idx] == nil then
return nil
end
if s.next_byte_idx > #(lines[s.next_line_idx]) then
s.next_line_idx = s.next_line_idx + 1
s.next_byte_idx = 1
return ('\n'):byte()
end
local ret = lines[s.next_line_idx]:byte(s.next_byte_idx)
if ret == ('\n'):byte() then
ret = 0 -- See :h NL-used-for-NUL.
end
s.next_byte_idx = s.next_byte_idx + 1
return ret
end
return next, init_s, nil
end
local function charblob_encode(lines, textwidth, indent)
local ret = {
'const unsigned char blob[] = {',
indent,
}
for byte in charblob_bytes_iter(lines) do
-- .- space + number (width 3) + comma
if #(ret[#ret]) + 5 > textwidth then
ret[#ret + 1] = indent
else
ret[#ret] = ret[#ret] .. ' '
end
ret[#ret] = ret[#ret] .. (('%3u,'):format(byte))
end
ret[#ret + 1] = '};'
return ret
end
return {
bytes_iter = charblob_bytes_iter,
encode = charblob_encode,
}
==============================================================================
Commands *lua-commands*
*:lua*
:[range]lua {chunk}
Execute Lua chunk {chunk}.
Examples:
>
:lua vim.api.nvim_command('echo "Hello, Nvim!"')
<
To see the Lua version: >
:lua print(_VERSION)
To see the LuaJIT version: >
:lua print(jit.version)
<
:[range]lua << [endmarker]
{script}
{endmarker}
Execute Lua script {script}. Useful for including Lua
code in Vim scripts.
The {endmarker} must NOT be preceded by any white space.
If [endmarker] is omitted from after the "<<", a dot '.' must be used after
{script}, like for the |:append| and |:insert| commands.
Example:
>
function! CurrentLineInfo()
lua << EOF
local linenr = vim.api.nvim_win_get_cursor(0)[1]
local curline = vim.api.nvim_buf_get_lines(
0, linenr, linenr + 1, false)[1]
print(string.format("Current line [%d] has %d bytes",
linenr, #curline))
EOF
endfunction
Note that the `local` variables will disappear when block finishes. This is
not the case for globals.
*:luado*
:[range]luado {body} Execute Lua function "function (line, linenr) {body}
end" for each line in the [range], with the function
argument being set to the text of each line in turn,
without a trailing <EOL>, and the current line number.
If the value returned by the function is a string it
becomes the text of the line in the current turn. The
default for [range] is the whole file: "1,$".
Examples:
>
:luado return string.format("%s\t%d", line:reverse(), #line)
:lua require"lpeg"
:lua -- balanced parenthesis grammar:
:lua bp = lpeg.P{ "(" * ((1 - lpeg.S"()") + lpeg.V(1))^0 * ")" }
:luado if bp:match(line) then return "-->\t" .. line end
<
*:luafile*
:[range]luafile {file}
Execute Lua script in {file}.
The whole argument is used as a single file name.
Examples:
>
:luafile script.lua
:luafile %
<
All these commands execute a Lua chunk from either the command line (:lua and
:luado) or a file (:luafile) with the given line [range]. Similarly to the Lua
interpreter, each chunk has its own scope and so only global variables are
shared between command calls. All Lua default libraries are available. In
addition, Lua "print" function has its output redirected to the Nvim message
area, with arguments separated by a white space instead of a tab.
Lua uses the "vim" module (see |lua-vim|) to issue commands to Nvim. However,
procedures that alter buffer content, open new buffers, and change cursor
position are restricted when the command is executed in the |sandbox|.
==============================================================================
luaeval() *lua-eval* *luaeval()*
The (dual) equivalent of "vim.eval" for passing Lua values to Nvim is
"luaeval". "luaeval" takes an expression string and an optional argument used
for _A inside expression and returns the result of the expression. It is
semantically equivalent in Lua to:
>
local chunkheader = "local _A = select(1, ...) return "
function luaeval (expstr, arg)
local chunk = assert(loadstring(chunkheader .. expstr, "luaeval"))
return chunk(arg) -- return typval
end
Lua nils, numbers, strings, tables and booleans are converted to their
respective VimL types. An error is thrown if conversion of any other Lua types
is attempted.
The magic global "_A" contains the second argument to luaeval().
Example: >
:echo luaeval('_A[1] + _A[2]', [40, 2])
42
:echo luaeval('string.match(_A, "[a-z]+")', 'XYXfoo123')
foo
Lua tables are used as both dictionaries and lists, so it is impossible to
determine whether empty table is meant to be empty list or empty dictionary.
Additionally lua does not have integer numbers. To distinguish between these
cases there is the following agreement:
0. Empty table is empty list.
1. Table with N incrementally growing integral numbers, starting from 1 and
ending with N is considered to be a list.
2. Table with string keys, none of which contains NUL byte, is considered to
be a dictionary.
3. Table with string keys, at least one of which contains NUL byte, is also
considered to be a dictionary, but this time it is converted to
a |msgpack-special-map|.
*lua-special-tbl*
4. Table with `vim.type_idx` key may be a dictionary, a list or floating-point
value:
- `{[vim.type_idx]=vim.types.float, [vim.val_idx]=1}` is converted to
a floating-point 1.0. Note that by default integral lua numbers are
converted to |Number|s, non-integral are converted to |Float|s. This
variant allows integral |Float|s.
- `{[vim.type_idx]=vim.types.dictionary}` is converted to an empty
dictionary, `{[vim.type_idx]=vim.types.dictionary, [42]=1, a=2}` is
converted to a dictionary `{'a': 42}`: non-string keys are ignored.
Without `vim.type_idx` key tables with keys not fitting in 1., 2. or 3.
are errors.
- `{[vim.type_idx]=vim.types.list}` is converted to an empty list. As well
as `{[vim.type_idx]=vim.types.list, [42]=1}`: integral keys that do not
form a 1-step sequence from 1 to N are ignored, as well as all
non-integral keys.
Examples: >
:echo luaeval('math.pi')
:function Rand(x,y) " random uniform between x and y
: return luaeval('(_A.y-_A.x)*math.random()+_A.x', {'x':a:x,'y':a:y})
: endfunction
:echo Rand(1,10)
Note that currently second argument to `luaeval` undergoes VimL to lua
conversion, so changing containers in lua do not affect values in VimL. Return
value is also always converted. When converting, |msgpack-special-dict|s are
treated specially.
==============================================================================
Lua standard modules *lua-stdlib*
The Nvim Lua "standard library" (stdlib) is the `vim` module, which exposes
various functions and sub-modules. It is always loaded, thus require("vim")
is unnecessary.
You can peek at the module properties: >
:lua print(vim.inspect(vim))
Result is something like this: >
{
_os_proc_children = <function 1>,
_os_proc_info = <function 2>,
...
api = {
nvim__id = <function 5>,
nvim__id_array = <function 6>,
...
},
deepcopy = <function 106>,
gsplit = <function 107>,
...
}
To find documentation on e.g. the "deepcopy" function: >
:help vim.deepcopy
Note that underscore-prefixed functions (e.g. "_os_proc_children") are
internal/private and must not be used by plugins.
------------------------------------------------------------------------------
VIM.API *lua-api*
`vim.api` exposes the full Nvim |API| as a table of Lua functions.
Example: to use the "nvim_get_current_line()" API function, call
"vim.api.nvim_get_current_line()": >
print(tostring(vim.api.nvim_get_current_line()))
------------------------------------------------------------------------------
VIM.LOOP *lua-loop*
`vim.loop` exposes all features of the Nvim event-loop. This is a lower-level
API that provides functionality for networking, filesystem, and process
management. Try this command to see available functions: >
:lua print(vim.inspect(vim.loop))
See http://docs.libuv.org for complete documentation.
See https://github.com/luvit/luv/tree/master/examples for examples.
*E5560* *lua-loop-callbacks*
Note: it is not allowed to directly invoke most of the Nvim API from `vim.loop`
callbacks. This will result in an error: >
local timer = vim.loop.new_timer()
timer:start(1000, 0, function()
vim.api.nvim_command('echomsg "test"')
end)
The `vim.schedule_wrap` helper can be used to defer the callback until it
is safe to execute API methods. >
local timer = vim.loop.new_timer()
timer:start(1000, 0, vim.schedule_wrap(function()
vim.api.nvim_command('echomsg "test"')
end))
A subset of the API is available in direct luv callbacks ("fast" callbacks),
most notably |nvim_get_mode()| and |nvim_input()|. It is possible to
check whether code is running in this context using |vim.in_fast_event()|.
Example: repeating timer
1. Save this code to a file.
2. Execute it with ":luafile %". >
-- Create a timer handle (implementation detail: uv_timer_t).
local timer = vim.loop.new_timer()
local i = 0
-- Waits 1000ms, then repeats every 750ms until timer:close().
timer:start(1000, 750, function()
print('timer invoked! i='..tostring(i))
if i > 4 then
timer:close() -- Always close handles to avoid leaks.
end
i = i + 1
end)
print('sleeping');
Example: TCP echo-server *tcp-server*
1. Save this code to a file.
2. Execute it with ":luafile %".
3. Note the port number.
4. Connect from any TCP client (e.g. "nc 0.0.0.0 36795"): >
local function create_server(host, port, on_connection)
local server = vim.loop.new_tcp()
server:bind(host, port)
server:listen(128, function(err)
assert(not err, err) -- Check for errors.
local sock = vim.loop.new_tcp()
server:accept(sock) -- Accept client connection.
on_connection(sock) -- Start reading messages.
end)
return server
end
local server = create_server('0.0.0.0', 0, function(sock)
sock:read_start(function(err, chunk)
assert(not err, err) -- Check for errors.
if chunk then
sock:write(chunk) -- Echo received messages to the channel.
else -- EOF (stream closed).
sock:close() -- Always close handles to avoid leaks.
end
end)
end)
print('TCP echo-server listening on port: '..server:getsockname().port)
------------------------------------------------------------------------------
VIM *lua-util*
vim.stricmp({a}, {b}) *vim.stricmp()*
Compares strings case-insensitively. Returns 0, 1 or -1 if strings
are equal, {a} is greater than {b} or {a} is lesser than {b},
respectively.
vim.schedule({callback}) *vim.schedule()*
Schedules {callback} to be invoked soon by the main event-loop. Useful
to avoid |textlock| or other temporary restrictions.
vim.in_fast_event() *vim.in_fast_event()*
Returns true if the code is executing as part of a "fast" event
handler, where most of the API is disabled. These are low-level event
such as luv callbacks |lua-loop-callbacks|, which can be invoked at
any time nvim polls for input. When this returns `false` most API
functions are callable, but can be subjected to other restrictions,
such as |textlock|.
vim.type_idx *vim.type_idx*
Type index for use in |lua-special-tbl|. Specifying one of the
values from |vim.types| allows typing the empty table (it is
unclear whether empty lua table represents empty list or empty array)
and forcing integral numbers to be |Float|. See |lua-special-tbl| for
more details.
vim.val_idx *vim.val_idx*
Value index for tables representing |Float|s. A table representing
floating-point value 1.0 looks like this: >
{
[vim.type_idx] = vim.types.float,
[vim.val_idx] = 1.0,
}
< See also |vim.type_idx| and |lua-special-tbl|.
vim.types *vim.types*
Table with possible values for |vim.type_idx|. Contains two sets
of key-value pairs: first maps possible values for |vim.type_idx|
to human-readable strings, second maps human-readable type names to
values for |vim.type_idx|. Currently contains pairs for `float`,
`array` and `dictionary` types.
Note: one must expect that values corresponding to `vim.types.float`,
`vim.types.array` and `vim.types.dictionary` fall under only two
following assumptions:
1. Value may serve both as a key and as a value in a table. Given the
properties of lua tables this basically means “value is not `nil`”.
2. For each value in `vim.types` table `vim.types[vim.types[value]]`
is the same as `value`.
No other restrictions are put on types, and it is not guaranteed that
values corresponding to `vim.types.float`, `vim.types.array` and
`vim.types.dictionary` will not change or that `vim.types` table will
only contain values for these three types.
==============================================================================
Lua module: vim *lua-vim*
inspect({object}, {options}) *vim.inspect()*
Return a human-readable representation of the given object.
See also: ~
https://github.com/kikito/inspect.lua
deepcopy({orig}) *vim.deepcopy()*
Returns a deep copy of the given object. Non-table objects are
copied as in a typical Lua assignment, whereas table objects
are copied recursively.
Parameters: ~
{orig} Table to copy
Return: ~
New table of copied keys and (nested) values.
gsplit({s}, {sep}, {plain}) *vim.gsplit()*
Splits a string at each instance of a separator.
Parameters: ~
{s} String to split
{sep} Separator string or pattern
{plain} If `true` use `sep` literally (passed to
String.find)
Return: ~
Iterator over the split components
See also: ~
|vim.split()|
https://www.lua.org/pil/20.2.html
http://lua-users.org/wiki/StringLibraryTutorial
split({s}, {sep}, {plain}) *vim.split()*
Splits a string at each instance of a separator.
Examples: >
split(":aa::b:", ":") --> {'','aa','','bb',''}
split("axaby", "ab?") --> {'','x','y'}
split(x*yz*o, "*", true) --> {'x','yz','o'}
<
Parameters: ~
{s} String to split
{sep} Separator string or pattern
{plain} If `true` use `sep` literally (passed to
String.find)
Return: ~
List-like table of the split components.
See also: ~
|vim.gsplit()|
tbl_contains({t}, {value}) *vim.tbl_contains()*
Checks if a list-like (vector) table contains `value` .
Parameters: ~
{t} Table to check
{value} Value to compare
Return: ~
true if `t` contains `value`
tbl_extend({behavior}, {...}) *vim.tbl_extend()*
Merges two or more map-like tables.
Parameters: ~
{behavior} Decides what to do if a key is found in more
than one map:
• "error": raise an error
• "keep": use value from the leftmost map
• "force": use value from the rightmost map
{...} Two or more map-like tables.
See also: ~
|extend()|
tbl_flatten({t}) *vim.tbl_flatten()*
Creates a copy of a list-like table such that any nested
tables are "unrolled" and appended to the result.
Parameters: ~
{t} List-like table
Return: ~
Flattened copy of the given list-like table.
trim({s}) *vim.trim()*
Trim whitespace (Lua pattern "%s") from both sides of a
string.
Parameters: ~
{s} String to trim
Return: ~
String with whitespace removed from its beginning and end
See also: ~
https://www.lua.org/pil/20.2.html
vim:tw=78:ts=8:ft=help:norl: