thiago-negri / ariadne

Go-to-definition for Haskell

Ariadne

Ariadne provides a "go-to-definition" functionality for Haskell.

Video demonstration

Usage

To use Ariadne, you need two things:

• install this package, ariadne, which includes the ariadne-server executable, and make sure this executable is running;
• find and install a plugin for your editor or IDE of choice.

Editor plugins

Currently, the following editor/IDE plugins exist:

• vim

Limitations

As of v0.1, Ariadne only knows about the current file. It won't find definitions in other files in the same directory, or in the installed packages. It also won't look in the Cabal file for the language extensions, and a file may fail to parse because of that.

These will be addressed in the future versions.

Creating a plugin

Writing a new Ariadne plugin should be straightforward (assuming you know how to extend your editor/IDE).

If you write a new plugin, let me know so I can update the list above, and also notify you when the protocol changes.

Conventions

In the protocol description below, we don't use Erlang's upper-case/lower-case convention, because it would confuse anyone except Erlang or Prolog programmers. Instead, variables and functions are written lowercase, and atoms are prefixed with the colon, e.g. :atom.

Protocol

You communicate with the Ariadne server via the BERT-RPC protocol over TCP. The server listens on the local TCP port 39014. The BERT-RPC module is ariadne.

The request has form

find(file, line, column)

where file is a binary string, line and column are integers. file must contain the full path to the Haskell source file. It is assumed to be UTF-8 encoded, although this may improve in the future.

The line and column should probably be the current cursor position. Ariadne will look up the name at that location. Lines and columns are numbered starting from 1.

The possible responses are:

{ :no_name }

This means that there's no recognized name at the given position. The plugin should probably do nothing in this case.

{ :loc_known, file, line, column }

This means that the name is defined at the given file, line, and column. The file is again a binary UTF-8 encoded full path. The plugin should probably jump at that location.

{ :loc_unknown, modname }

We don't know where the name is defined, but we know it comes from the given module (binary UTF-8 encoded name). The plugin may want to show this information to the user.

{ :error, message }

Some error has occurred. For example, the file has a syntax or scoping error. The plugin is expected to present the error message to the user.

The message is a binary UTF-8 encoded text, possibly spanning multiple lines.

Other requests and responses will probably be added in the future versions.