micro/runtime/help/plugins.md

# Plugins

Micro supports creating plugins with a simple Lua system. Every plugin has a
main script which is run at startup which should be placed in 
`~/.config/micro/plugins/pluginName/pluginName.lua`.

There are a number of callback functions which you can create in your plugin to
run code at times other than startup. The naming scheme is `onAction(view)`. For
example a function which is run every time the user saves the buffer would be:

```lua
function onSave(view)
    ...
    return false
end
```

The `view` variable is a reference to the view the action is being executed on.
This is almost always the current view, which you can get with `CurView()` as
well.

All available actions are listed in the keybindings section of the help.

For callbacks to mouse actions, you are also given the event info:

```lua
function onMousePress(view, event)
    local x, y = event:Position()

    return false
end
```

These functions should also return a boolean specifying whether the view should
be relocated to the cursor or not after the action is complete.

Note that these callbacks occur after the action has been completed. If you want
a callback before the action is executed, use `preAction()`. In this case the
boolean returned specifies whether or not the action should be executed after
the lua code completes.

Another useful callback to know about which is not an action is
`onViewOpen(view)` which is called whenever a new view is opened and the new
view is passed in. This is useful for setting local options based on the
filetype, for example turning off `tabstospaces` only for Go files when they are
opened.

---

There are a number of functions and variables that are available to you in order
to access the inner workings of micro. Here is a list (the type signatures for
functions are given using Go's type system):

* `OS`: variable which gives the OS micro is currently running on (this is the
  same as Go's GOOS variable, so `darwin`, `windows`, `linux`, `freebsd`...)

* `configDir`: contains the path to the micro configuration files

* `tabs`: a list of all the tabs currently in use

* `curTab`: the index of the current tabs in the tabs list

* `messenger`: lets you send messages to the user or create prompts

* `NewBuffer(text, path string) *Buffer`: creates a new buffer from a given
   reader with a given path

* `NewBufferFromFile(path string) *Buffer`: creates a new buffer from a given
   path

* `GetLeadingWhitespace() bool`: returns the leading whitespace of the given
   string

* `IsWordChar(str string) bool`: returns whether or not the string is a 'word
   character'

* `RuneStr(r rune) string`: returns a string containing the given rune

* `Loc(x, y int) Loc`: returns a new `Loc` struct

* `WorkingDirectory() string`: returns a rooted path name to the current working
   directory

* `JoinPaths(dir... string) string`: combines multiple directories to a full
   path

* `DirectoryName(path string)`: returns all but the last element of path,
   typically the path's directory

* `GetOption(name string)`: returns the value of the requested option

* `AddOption(name string, value interface{})`: sets the given option with the
   given value (`interface{}` means any type in Go)

* `SetOption(option, value string)`: sets the given option to the value. This
   will set the option globally, unless it is a local only option.

* `SetLocalOption(option, value string, view *View)`: sets the given option to
   the value locally in the given buffer

* `BindKey(key, action string)`: binds `key` to `action`

* `MakeCommand(name, function string, completions ...Completion)`: 
   creates a command with `name` which will call `function` when executed. Use 0
   for completions to get NoCompletion.

* `MakeCompletion(function string)`:
   creates a `Completion` to use with `MakeCommand`

* `CurView()`: returns the current view

* `HandleCommand(cmd string)`: runs the given command

* `ExecCommand(name string, args []string) (string, error)`: exec a (shell) command with the
   given arguments. Returns the command's output and a possible error.

* `RunShellCommand(cmd string) (string, error)`: Run a shell command. This uses `ExecCommand`
   under the hood but also does some parsing for the arguments (i.e. quoted arguments). The
   function returns the command's output and a possible error.

* `RunBackgroundShell(cmd string)`: Run a shell command in the background.

* `RunInteractiveShell(cmd string, wait bool, getOutput bool) (string, error)`: Run a shell command
   by closing micro and running the command interactively. If `wait` is true, a prompt will be
   used after the process exits to prevent the terminal from immediately returning to micro, allowing
   the user to view the output of the process. If `getOutput` is true, the command's standard output
   will be returned. Note that if `getOutput` is true, some interactive commands may not behave
   normally because `isatty` will return false.

* `RunTermEmulator(cmd string, wait bool, getOutput bool, callback string) error`: Same as
   `RunInteractiveShell` except the command is run within the current split in a terminal emulator.
   The `callback` input is a string callback to a lua function which will be called when the process
   exits. The output of the process will be provided as the first and only argument to the callback
   (it will be empty if `getOutput` is false).
   Note that this functionality is only supported on some operating systems (linux, darwin, dragonfly,
   openbsd, freebsd). Use the `TermEmuSupported` (see below) boolean to determine if the current
   system is supported.

* `TermEmuSupported`: Boolean specifying if the terminal emulator is supported on the version of
   micro that is running.

* `ToCharPos(loc Loc, buf *Buffer) int`: returns the character position of a
   given x, y location

* `Reload`: (Re)load everything

* `ByteOffset(loc Loc, buf *Buffer) int`: exactly like `ToCharPos` except it it
   counts bytes instead of runes

* `JobSpawn(cmdName string, cmdArgs []string, onStdout, onStderr, onExit string, userargs ...string)`:
   Starts running the given process in the background. `onStdout` `onStderr` and
   `onExit` are callbacks to lua functions which will be called when the given
   actions happen to the background process. `userargs` are the arguments which
   will get passed to the callback functions

* `JobStart(cmd string, onStdout, onStderr, onExit string, userargs ...string)`:
   Starts running the given shell command in the background. Note that the
   command execute is first parsed by a shell when using this command. It is
   executed with `sh -c`.

* `JobSend(cmd *exec.Cmd, data string)`: send a string into the stdin of the job
   process

* `JobStop(cmd *exec.Cmd)`: kill a job

This may seem like a small list of available functions but some of the objects
returned by the functions have many methods. `CurView()` returns a view object
which has all the actions which you can call. For example
`CurView():Save(false)`. You can see the full list of possible actions in the
keybindings help topic. The boolean on all the actions indicates whether or not
the lua callbacks should be run. I would recommend generally sticking to false
when making a plugin to avoid recursive problems, for example if you call
`CurView():Save(true)` in `onSave()`. Just use `CurView():Save(false)` so that
it won't call `onSave()` again.

Using the view object, you can also access the buffer associated with that view
by using `CurView().Buf`, which lets you access the `FileType`, `Path`,
`Name`...

The possible methods which you can call using the `messenger` variable are:

* `messenger.Message(msg ...interface{})`
* `messenger.Error(msg ...interface{})`
* `messenger.YesNoPrompt(prompt string) (bool,bool)`
* `messenger.Prompt(prompt, historyType string, completionType Completion) (string, bool)`
* `messenger.AddLog(msg ...interface{})`

#### Note 

Go function signatures use `.` and lua uses `:` so

```go
messenger.Message()
```

turns to

```lua
messenger:Message()
```

If you want a standard prompt, just use

```lua
messenger:Prompt(prompt, "", 0)
```

Debug or logging your plugin can be done with below lua example code.

```lua
messenger:AddLog("Message goes here ",pluginVariableToPrintHere)
```

In Micro to see your plugin logging output press `CtrlE` then type `log`, a 
logging window will open and any logging sent from your plugin will be displayed
here.


## Accessing the Go standard library

It is possible for your lua code to access many of the functions in the Go
standard library.

Simply import the package you'd like and then you can use it. For example:

```lua
local ioutil = import("io/ioutil")
local fmt = import("fmt")

local data, err = ioutil.ReadFile("SomeFile.txt")

if err ~= nil then
    messenger:Error("Error reading file: SomeFile.txt")
else
    -- Data is returned as an array of bytes
    -- Using Sprintf will convert it to a string
    local str = fmt.Sprintf("%s", data)

    -- Do something with the file you just read!
    -- ...
end
```

Here are the packages from the Go standard library that you can access.
Nearly all functions from these packages are supported. For an exact
list of which functions are supported you can look through `lua.go`
(which should be easy to understand).

```
fmt
io
io/ioutil
net
math
math/rand
os
runtime
path
filepath
strings
regexp
errors
time
```

For documentation for each of these functions, you can simply look
through the Go standard library documentation.

## Adding help files, syntax files, or colorschemes in your plugin

You can use the `AddRuntimeFile(name, type, path string)` function to add
various kinds of files to your plugin. For example, if you'd like to add a help
topic to your plugin called `test`, you would create a `test.md` file, and call
the function:

```lua
AddRuntimeFile("test", "help", "test.md")
```

Use `AddRuntimeFilesFromDirectory(name, type, dir, pattern)` to add a number of
files to the runtime. To read the content of a runtime file use
`ReadRuntimeFile(fileType, name string)` or `ListRuntimeFiles(fileType string)`
for all runtime files.


## Autocomplete command arguments

See this example to learn how to use `MakeCompletion` and `MakeCommand`

```lua
local function StartsWith(String,Start)
    String = String:upper()
    Start = Start:upper() 
    return string.sub(String,1,string.len(Start))==Start
end

function complete(input)
    local allCompletions = {"Hello", "World", "Foo", "Bar"}
    local result = {}

    for i,v in pairs(allCompletions) do
        if StartsWith(v, input) then
            table.insert(result, v)
        end
    end
    return result
end

function foo(arg)
    messenger:Message(arg)
end

MakeCommand("foo", "example.foo", MakeCompletion("example.complete"))
```


## Default plugins

For examples of plugins, see the default `autoclose` and `linter` plugins
(stored in the normal micro core repo under `runtime/plugins`) as well as any
plugins that are stored in the official channel
[here](https://github.com/micro-editor/plugin-channel).


## Plugin Manager

Micro also has a built in plugin manager which you can invoke with the
`> plugin ...` command.

For the valid commands you can use, see the `commands` help topic.

The manager fetches plugins from the channels (which is simply a list of plugin
metadata) which it knows about. By default, micro only knows about the official
channel which is located at github.com/micro-editor/plugin-channel but you can
add your own third-party channels using the `pluginchannels` option and you can
directly link third-party plugins to allow installation through the plugin
manager with the `pluginrepos` option.

If you'd like to publish a plugin you've made as an official plugin, you should
upload your plugin online (to Github preferably) and add a `repo.json` file.
This file will contain the metadata for your plugin. Here is an example:

```json
[{
  "Name": "pluginname",
  "Description": "Here is a nice concise description of my plugin",
  "Tags": ["python", "linting"],
  "Versions": [
    {
      "Version": "1.0.0",
      "Url": "https://github.com/user/plugin/archive/v1.0.0.zip",
      "Require": {
        "micro": ">=1.0.3"
      }
    }
  ]
}]
```

Then open a pull request at github.com/micro-editor/plugin-channel adding a link
to the raw `repo.json` that is in your plugin repository. To make updating the
plugin work, the first line of your plugins lua code should contain the version
of the plugin. (Like this: `VERSION = "1.0.0"`) Please make sure to use
[semver](http://semver.org/) for versioning.