Initial draft for a server supporting code completion

.gitignore

@@ -0,0 +1,18 @@
+.rebar3
+_*
+.eunit
+*.o
+*.beam
+*.plt
+*.swp
+*.swo
+.erlang.cookie
+ebin
+log
+erl_crash.dump
+.rebar
+logs
+_build
+.idea
+*.iml
+rebar3.crashdump

LICENSE

@@ -175,18 +175,7 @@
 
    END OF TERMS AND CONDITIONS
 
-   APPENDIX: How to apply the Apache License to your work.
-
-      To apply the Apache License to your work, attach the following
-      boilerplate notice, with the fields enclosed by brackets "[]"
-      replaced with your own identifying information. (Don't include
-      the brackets!)  The text should be enclosed in the appropriate
-      comment syntax for the file format. We also recommend that a
-      file or class name and description of purpose be included on the
-      same "printed page" as the copyright notice for easier
-      identification within third-party archives.
-
-   Copyright [yyyy] [name of copyright owner]
+   Copyright 2018, Roberto Aloi.
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

README.md

@@ -1,5 +1,51 @@
-# erlang-ls
-The Erlang Language Server Protocol Implementation
+erlang_ls
+=====
 
-# Get in Touch
-This project is still in a very early stage. To get in touch, feel free to join the #language-server channel in the Erlanger Slack.
+An Erlang server using Microsoft's Language Server Protocol 3.0.
+
+Get in Touch
+----
+
+This project is still in a very early stage. To get
+in touch, feel free to join the #language-server channel in the
+Erlanger Slack.
+
+Dev Quickstart
+-----
+
+    $ rebar3 shell
+    application:ensure_all_started(erlang_ls).
+    Opts = [{msgs, 1000}, {time, 99999}, {print_file, "/tmp/redbug"}],
+    redbug:start("erlang_ls_protocol->return", Opts).
+
+Emacs Setup
+-----
+
+    ;; Language Server Protocol Tests
+    (require 'lsp-mode)
+
+    ;; Enable code completion
+    (require 'company-lsp)
+    (push 'company-lsp company-backends)
+
+    ;; Connect to an already started language server
+    (lsp-define-tcp-client
+     lsp-erlang-mode
+     "erlang"
+     (lambda () default-directory)
+     '("/usr/local/opt/coreutils/libexec/gnubin/false")
+     "localhost"
+     9000)
+
+    (add-hook 'erlang-mode #'lsp-erlang-mode-enable)
+
+Manual enable the server for a buffer:
+
+M-x company-mode
+M-x company-lsp
+M-x lsp-erlang-mode-enable
+
+References
+-----
+
+https://microsoft.github.io/language-server-protocol/

rebar.config

@@ -0,0 +1,6 @@
+{erl_opts, [debug_info]}.
+{deps, [ {ranch,  "1.5.0"}
+       , {jsx,    "2.9.0"}
+       , {cowlib, "2.3.0"}
+       , {redbug, "1.2.0"}
+       ]}.

rebar.lock

@@ -0,0 +1,12 @@
+{"1.1.0",
+[{<<"cowlib">>,{pkg,<<"cowlib">>,<<"2.3.0">>},0},
+ {<<"jsx">>,{pkg,<<"jsx">>,<<"2.9.0">>},0},
+ {<<"ranch">>,{pkg,<<"ranch">>,<<"1.5.0">>},0},
+ {<<"redbug">>,{pkg,<<"redbug">>,<<"1.2.0">>},0}]}.
+[
+{pkg_hash,[
+ {<<"cowlib">>, <<"BBD58EF537904E4F7C1DD62E6AA8BC831C8183CE4EFA9BD1150164FE15BE4CAA">>},
+ {<<"jsx">>, <<"D2F6E5F069C00266CAD52FB15D87C428579EA4D7D73A33669E12679E203329DD">>},
+ {<<"ranch">>, <<"F04166F456790FEE2AC1AA05A02745CC75783C2BFB26D39FAF6AEFC9A3D3A58A">>},
+ {<<"redbug">>, <<"75C09B306471CEE01AC4BDB727C33CA671A48D7AB7ACAF090C557F2E5BC02620">>}]}
+].

src/erlang_ls.app.src

@@ -0,0 +1,19 @@
+{application, erlang_ls,
+ [{description, "An OTP application"},
+  {vsn, "0.1.0"},
+  {registered, []},
+  {mod, { erlang_ls_app, []}},
+  {applications,
+   [ kernel
+   , stdlib
+   , ranch
+   , jsx
+   , cowlib
+   ]},
+  {env,[]},
+  {modules, []},
+
+  {maintainers, []},
+  {licenses, ["Apache 2.0"]},
+  {links, []}
+ ]}.

src/erlang_ls_app.erl

@@ -0,0 +1,40 @@
+%%==============================================================================
+%% Application Callback Module
+%%==============================================================================
+-module(erlang_ls_app).
+
+%%==============================================================================
+%% Behaviours
+%%==============================================================================
+-behaviour(application).
+
+%%==============================================================================
+%% Exports
+%%==============================================================================
+
+%% Application Callbacks
+-export([ start/2
+        , stop/1
+        ]).
+
+%%==============================================================================
+%% Defines
+%%==============================================================================
+-define(DEFAULT_PORT, 9000).
+
+%%==============================================================================
+%% Application Callbacks
+%%==============================================================================
+-spec start(normal, any()) -> {ok, pid()}.
+start(_StartType, _StartArgs) ->
+  {ok, _} = ranch:start_listener( erlang_ls
+                                , ranch_tcp
+                                , [{port, ?DEFAULT_PORT}]
+                                , erlang_ls_protocol
+                                , []
+                                ),
+  erlang_ls_sup:start_link().
+
+-spec stop(any()) -> ok.
+stop(_State) ->
+  ok.

src/erlang_ls_protocol.erl

@@ -0,0 +1,199 @@
+%%==============================================================================
+%% The Language Server Protocol Implementation
+%%==============================================================================
+-module(erlang_ls_protocol).
+
+%%==============================================================================
+%% Behaviours
+%%==============================================================================
+-behaviour(ranch_protocol).
+-behaviour(gen_statem).
+
+%%==============================================================================
+%% Exports
+%%==============================================================================
+
+%% ranch_protocol callbacks
+-export([ start_link/4 ]).
+
+%% gen_statem callbacks
+-export([ callback_mode/0
+        , code_change/4
+        , init/1
+        , terminate/3
+        ]).
+
+%% gen_statem state functions
+-export([ connected/3
+        ]).
+
+%%==============================================================================
+%% Defines
+%%==============================================================================
+-define(JSONRPC_VSN, <<"2.0">>).
+
+%%==============================================================================
+%% Record Definitions
+%%==============================================================================
+-record(state, { socket
+               , transport
+               , text
+               }).
+
+%%==============================================================================
+%% Type Definitions
+%%==============================================================================
+-type state()        :: #state{}.
+-type request()      :: #{}.
+-type response()     :: #{}.
+-type result()       :: #{}.
+
+%%==============================================================================
+%% ranch_protocol callbacks
+%%==============================================================================
+-spec start_link(ramnch:ref(), any(), module(), any()) -> {ok, pid()}.
+start_link(Ref, Socket, Transport, Opts) ->
+  {ok, proc_lib:spawn_link(?MODULE, init, [{Ref, Socket, Transport, Opts}])}.
+
+%%==============================================================================
+%% gen_statem callbacks
+%%==============================================================================
+-spec callback_mode() -> state_functions.
+callback_mode() ->
+  state_functions.
+
+-spec init({ranch:ref(), any(), module(), any()}) -> no_return().
+init({Ref, Socket, Transport, _Opts}) ->
+  ok = ranch:accept_ack(Ref),
+  ok = Transport:setopts(Socket, [{active, true}, {packet, 0}]),
+  gen_statem:enter_loop( ?MODULE
+                       , []
+                       , connected
+                       , #state{ socket    = Socket
+                               , transport = Transport
+                               }
+                       ).
+
+-spec code_change(any(), atom(), state(), any()) -> {ok, atom(), state()}.
+code_change(_OldVsn, StateName, State, _Extra) ->
+  {ok, StateName, State}.
+
+-spec terminate(any(), atom(), state()) -> any().
+terminate(_Reason, _StateName, #state{ socket    = Socket
+                                     , transport = Transport
+                                     }) ->
+  Transport:close(Socket),
+  ok.
+
+%%==============================================================================
+%% gen_statem State Functions
+%%==============================================================================
+-spec connected(gen_statem:event_type(), any(), state()) -> any().
+connected(info, {tcp, Socket, Data}, #state{ socket = Socket } = State) ->
+  handle_request(Data, State);
+connected(info, {tcp_closed, _Socket}, _State) ->
+  {stop, normal};
+connected(info, {tcp_error, _, Reason}, _State) ->
+  {stop, Reason}.
+
+%%==============================================================================
+%% Internal Functions
+%%==============================================================================
+-spec handle_request(binary(), state()) -> any().
+handle_request(Data, #state{ socket    = Socket
+                           , transport = Transport
+                           } = State) ->
+  Request   = parse_data(Data),
+  Method    = maps:get(<<"method">>, Request),
+  Params    = maps:get(<<"params">>, Request),
+  case handle_request(Method, Params, State) of
+    {Result, NewState} ->
+      RequestId = maps:get(<<"id">>, Request),
+      Response  = build_response(RequestId, Result),
+      reply(Socket, Transport, Response),
+      {keep_state, NewState};
+    {NewState}         ->
+      {keep_state, NewState}
+  end.
+
+-spec handle_request(binary(), map(), state()) ->
+  {result(), state()} | {state()}.
+handle_request(<<"initialize">>, _Params, State) ->
+  Result = #{ capabilities =>
+                #{ completionProvider =>
+                     #{ resolveProvider => false
+                      , triggerCharacters => [<<":">>]
+                      }
+                 , textDocumentSync => 1
+                 }
+            },
+  {Result, State};
+handle_request(<<"initialized">>, _, State) ->
+  {State};
+handle_request(<<"textDocument/didOpen">>, Params, State) ->
+  TextDocument   = maps:get(<<"textDocument">>, Params),
+  Text           = maps:get(<<"text">>        , TextDocument),
+  {State#state{ text = Text }};
+handle_request(<<"textDocument/didChange">>, Params, State) ->
+  ContentChanges = maps:get(<<"contentChanges">>, Params),
+  case ContentChanges of
+    []                      -> {State};
+    [#{<<"text">> := Text}] -> {State#state{ text = Text }}
+  end;
+handle_request(<<"textDocument/hover">>, _Params, State) ->
+  {null, State};
+handle_request(<<"textDocument/completion">>, Params, #state{ text = Text
+                                                            } = State) ->
+  Position    = maps:get(<<"position">> , Params),
+  Line        = maps:get(<<"line">>     , Position),
+  Character   = maps:get(<<"character">>, Position),
+  Completions = get_completions(Text, Line, Character),
+  Result      = [#{label => C} || C <- Completions],
+  {Result, State};
+handle_request(Method, _Params, State) ->
+  erlang:display({not_implemented, Method}),
+  {State}.
+
+-spec parse_data(binary()) -> request().
+parse_data(Data) ->
+  {_Headers, Body} = cow_http:parse_headers(Data),
+  jsx:decode(Body, [return_maps]).
+
+-spec build_response(integer(), result()) -> response().
+build_response(RequestId, Result) ->
+  #{ jsonrpc => ?JSONRPC_VSN
+   , result  => Result
+   , id      => RequestId
+   }.
+
+-spec reply(any(), module(), response()) -> ok.
+reply(Socket, Transport, Response) ->
+  Body    = jsx:encode(Response),
+  Headers = io_lib:format("Content-Length: ~p\r\n", [byte_size(Body)]),
+  Data    = [Headers, "\r\n", Body],
+  Transport:send(Socket, Data).
+
+-spec get_completions(binary(), integer(), integer()) -> [binary()].
+get_completions(Text, Line, Character) ->
+  LineText        = get_line_text(Text, Line),
+  LineBeforeChar  = binary:part(LineText, {0, Character - 1}),
+  {ok, Tokens, _} = erl_scan:string(binary_to_list(LineBeforeChar)),
+  [H| _] = lists:reverse(Tokens),
+  Info = case H of
+           {atom, _, Atom} ->
+             try Atom:module_info(exports)
+             catch _:_ -> []
+             end;
+           _ ->
+             []
+         end,
+  [function_name_to_binary(M, A) || {M, A} <- Info].
+
+-spec get_line_text(binary(), integer()) -> binary().
+get_line_text(Text, Line) ->
+  Lines = binary:split(Text, <<"\n">>, [global]),
+  lists:nth(Line + 1, Lines).
+
+-spec function_name_to_binary(module(), non_neg_integer()) -> binary().
+function_name_to_binary(Module, Arity) ->
+  list_to_binary(io_lib:format("~p/~p", [Module, Arity])).