Neovim API for Haskell plugins as well as a plugin provider. This library and executable should provide a basis for developing plugins. This package should only contain broadly useful interfaces to write plugins for neovim in haskell. The design goal is to create an easy to use API that avoids most of the boilerplate while still retaining some sense of reliability and type safety. Since Template Haskell is used to generate the neovim bindings and to avoid some of the boilerplate handy work, some exotic operating systems and architectures may not work.

Build Status Hackage version nvim-hs on latest Stackage LTS nvim-hs on Stackage Nightly

What do I have to expect if I were to use it now?

Check the issue list here on github.

How do I start using this?

You need to install a neovim plugin that manages starting of nvim-hs plugins. Just follow the instructions here: nvim-hs.vim

Once you have installed that plugin, you can use nvim-hs plugins as you would normal vim plugins. Every plugin is started as a separate process which should be fine unless you have a lot of them.

You only have to read on if you want to start “scripting” functions or plugins yourself in Haskell.

Scripting with Haskell

The entry point for all Haskell-based scripts is a plugin. An nvim-hs plugin is a plain Haskell project with two conventions:

  1. You need an executable that starts a msgpack-rpc compatible client.

  2. You need a tiny bit of vimL in your runtime path that starts the plugin.

The simplest way to get started is the stack template from this repository/package inside your neovim configuration folder which will be described here. (Alternatively, you can manually create a project and do everything that is explained in :help nvim-hs.txt which should be available if you installed the plugin mentioned in the previous section.)

You need to install stack and have the neovim executable on the path. (The API code generation calls nvim --api-info.)

Afterwards, you switch to your neovim configuration folder (typically ~/.config/nvim) and you have to create your plugin project.

cd ~/.config/nvim

stack new my-nvim-hs https://raw.githubusercontent.com/neovimhaskell/nvim-hs/master/stack-template.hsfiles –bare –omit-packages –ignore-subdirs

If you start neovim now, it will compile the example plugins which may take a few minutes. Once it is started you can use the predefined functions from the template.

:echo NextRandom()

should print a random number.

To start writing your own functions and plugins, read through the files generated by the template accompanied by the library documentation on hackage.


Documentation, typo fixes and alike will almost always be merged.

If you want to bring forward new features or convenience libraries for interacting with neovim, you should create an issue first. The features of this (cabal) project should be kept small as this helps reducing the development time. (For some tests it is necessary to issue cabal install, so any change to to a module can significantly increase the compilation time.) If your idea solves a general problem, feel free to open an issue in the library project of nvim-hs: nvim-hs-contrib


  • Your configuration is now just a Haskell project. The dependency to Dyre has been removed and you are now forced to write a line of vimL and add a normal nvim-plugin to your setup. The template still does set everything up for you. The distinction between a plugin and a personal nvim-hs configuration is now gone and apart from settings things up, nothing has changed in this regard. The nvim-plugin contains the necessary documentation on what to do and should be available with :help nvim-hs when installed correctly.

  • Since basically all generated functions were throwing exceptions anyway, the primed functions have become the default and if you want to explicitly handle error cases, you have to surround your code with catch or something more appropriate from UnliftIO.Exception. You have to remove ' from your API calls or you have to adjust your error handling.

  • There are now three flavors of APIs and you have to import one additionally to importing the Neovim module:

    • Neovim.API.Text: This uses strict Text for strings and Vector as lists. This is the recommended API to use.

    • Neovim.API.String: This is the same as before. Strings are String and lists are []. This is for the lazy and backwards-ish compatiblity.

    • Neovim.API.ByteString: This can be useful for really performance critical stuff or if you`re writing a plugin for binary files.

  • The Neovim.Debug module is now more pleasant to use.

  • With the api of neovim 0.3.0, a function was exposed that had a reserved haskell keyword as a parameter name. The code generation did not sanitize this. This bugfix releases resolves this.

  • Each plugin (type) now defines an environment which is similar to how stateful plugins have been declared in previous versions. If you need multiple different environments for different functions, you can make them fields of a bigger environment or define multiple plugin values.

    The type Neovim r st a has become Neovim env a where env is technically equivalent to the previous r. I was mainly motivated by this blog post:


  • Only works with ghc >= 8. I removed some backwards compatibility. If you need older ghc versions, just use the previous version (0.2.5) as the feature set hasn’t really changed.

  • A different pretty printer library is now used and may surface at some places.

  • Functions do now time out after some time, 10 seconds for those that block neovim and 10 minutes for background functions.

  • A few types have been adjusted.

  • Some improvement in error reporting.


  • Older versions of nvim-hs may not function if some versions of a dependency are used. This version has proper bounds for the dependency and should cause a compile time failure if an incompatible version of the dependency is used (see #61).


  • Replace error code of remote functions to return Either NeovimException a instead of a generic messagepack Object

  • Export API functions that throw a NeovimException instead of returning Either NeovimExeception a.

  • Replace three element tuple for stateful function declaration (#53)

  • Add a stack template for easier setup

  • Exceptions from pure code are now caught (#48)


  • Adjust parser for output of nvim --api-info

  • Adjust parser of ConfigHelper plugin


  • Adjust handling of string sent by neovim in API generation.


  • Noteworthy new API functions for the user’s convenience:

    • errOnInvalidResult
    • (:+)
  • ansi-wl-pprint is used for pretty printing of various things now. Most notably, the error type has been changed from String to Doc. This is a breaking change, but it was kind of announced in the issues list. In any case, uses of err can be fixed by enabling the OverloadedStrings extension. Other breakages have to be fixed by hand.


  • Documentation received some love.

  • A few renames of repurposed internals.


  • Debugging facilities for ghci have been added. Check out the Neovim.Debug module! These few functions are very valuable to debug your code or even the code of nvim-hs itself.

  • Startup code now has a special Neovim environment which has access to some of the internals that may or may not be useful. This change allowed the ConfigHelper plugin to be included as a normal, separable plugin. Unfortunately, this potentially breaks the plugin startup code of some existing plugins.

  • Neovim context is no longer a type synonym, but a newtype wrapper around the previous type synonym with an added ResourceT wrapper. The functions from MonadReader are now actually exported as those.

    As a consequence, some of your code may break if you lack some specific instances which were auto-derived before. Send a PR or open a ticket to resolve this.

  • Add handling for some kind of variadic arguments handling.

    A command or function will be passed Nothing as it’s last arguments if the argument type is wrapped in Maybe and the invocation on the side of neovim did not pass those arguments.


  • Add handling for special command options

    This breaks code that used command or command' to export functionality. You should replace the options with a list of CommandOptions.

    An export like $(command' foo) def { cmdSync = Async } must be redefined to $(command' foo) [CmdSync Async].


  • Usable prototype implementation
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