path: root/runtime/lua/vim/lsp/rpc.lua

local vim = vim
local uv = vim.loop
local log = require('vim.lsp.log')
local protocol = require('vim.lsp.protocol')
local validate, schedule, schedule_wrap = vim.validate, vim.schedule, vim.schedule_wrap

---@private
--- Checks whether a given path exists and is a directory.
---@param filename (string) path to check
---@returns (bool)
local function is_dir(filename)
  local stat = vim.loop.fs_stat(filename)
  return stat and stat.type == 'directory' or false
end

---@private
--- Merges current process env with the given env and returns the result as
--- a list of "k=v" strings.
---
--- <pre>
--- Example:
---
---  in:    { PRODUCTION="false", PATH="/usr/bin/", PORT=123, HOST="0.0.0.0", }
---  out:   { "PRODUCTION=false", "PATH=/usr/bin/", "PORT=123", "HOST=0.0.0.0", }
--- </pre>
---@param env (table) table of environment variable assignments
---@returns (table) list of `"k=v"` strings
local function env_merge(env)
  if env == nil then
    return env
  end
  -- Merge.
  env = vim.tbl_extend('force', vim.fn.environ(), env)
  local final_env = {}
  for k,v in pairs(env) do
    assert(type(k) == 'string', 'env must be a dict')
    table.insert(final_env, k..'='..tostring(v))
  end
  return final_env
end

---@private
--- Embeds the given string into a table and correctly computes `Content-Length`.
---
---@param encoded_message (string)
---@returns (table) table containing encoded message and `Content-Length` attribute
local function format_message_with_content_length(encoded_message)
  return table.concat {
    'Content-Length: '; tostring(#encoded_message); '\r\n\r\n';
    encoded_message;
  }
end

---@private
--- Parses an LSP Message's header
---
---@param header: The header to parse.
---@returns Parsed headers
local function parse_headers(header)
  if type(header) ~= 'string' then
    return nil
  end
  local headers = {}
  for line in vim.gsplit(header, '\r\n', true) do
    if line == '' then
      break
    end
    local key, value = line:match("^%s*(%S+)%s*:%s*(.+)%s*$")
    if key then
      key = key:lower():gsub('%-', '_')
      headers[key] = value
    else
      local _ = log.error() and log.error("invalid header line %q", line)
      error(string.format("invalid header line %q", line))
    end
  end
  headers.content_length = tonumber(headers.content_length)
      or error(string.format("Content-Length not found in headers. %q", header))
  return headers
end

-- This is the start of any possible header patterns. The gsub converts it to a
-- case insensitive pattern.
local header_start_pattern = ("content"):gsub("%w", function(c) return "["..c..c:upper().."]" end)

---@private
--- The actual workhorse.
local function request_parser_loop()
  local buffer = '' -- only for header part
  while true do
    -- A message can only be complete if it has a double CRLF and also the full
    -- payload, so first let's check for the CRLFs
    local start, finish = buffer:find('\r\n\r\n', 1, true)
    -- Start parsing the headers
    if start then
      -- This is a workaround for servers sending initial garbage before
      -- sending headers, such as if a bash script sends stdout. It assumes
      -- that we know all of the headers ahead of time. At this moment, the
      -- only valid headers start with "Content-*", so that's the thing we will
      -- be searching for.
      -- TODO(ashkan) I'd like to remove this, but it seems permanent :(
      local buffer_start = buffer:find(header_start_pattern)
      local headers = parse_headers(buffer:sub(buffer_start, start-1))
      local content_length = headers.content_length
      -- Use table instead of just string to buffer the message. It prevents
      -- a ton of strings allocating.
      -- ref. http://www.lua.org/pil/11.6.html
      local body_chunks = {buffer:sub(finish+1)}
      local body_length = #body_chunks[1]
      -- Keep waiting for data until we have enough.
      while body_length < content_length do
        local chunk = coroutine.yield()
            or error("Expected more data for the body. The server may have died.") -- TODO hmm.
        table.insert(body_chunks, chunk)
        body_length = body_length + #chunk
      end
      local last_chunk = body_chunks[#body_chunks]

      body_chunks[#body_chunks] = last_chunk:sub(1, content_length - body_length - 1)
      local rest = ''
      if body_length > content_length then
        rest = last_chunk:sub(content_length - body_length)
      end
      local body = table.concat(body_chunks)
      -- Yield our data.
      buffer = rest..(coroutine.yield(headers, body)
          or error("Expected more data for the body. The server may have died.")) -- TODO hmm.
    else
      -- Get more data since we don't have enough.
      buffer = buffer..(coroutine.yield()
          or error("Expected more data for the header. The server may have died.")) -- TODO hmm.
    end
  end
end

local client_errors = vim.tbl_add_reverse_lookup {
  INVALID_SERVER_MESSAGE       = 1;
  INVALID_SERVER_JSON          = 2;
  NO_RESULT_CALLBACK_FOUND     = 3;
  READ_ERROR                   = 4;
  NOTIFICATION_HANDLER_ERROR   = 5;
  SERVER_REQUEST_HANDLER_ERROR = 6;
  SERVER_RESULT_CALLBACK_ERROR = 7;
}

--- Constructs an error message from an LSP error object.
---
---@param err (table) The error object
---@returns (string) The formatted error message
local function format_rpc_error(err)
  validate {
    err = { err, 't' };
  }

  -- There is ErrorCodes in the LSP specification,
  -- but in ResponseError.code it is not used and the actual type is number.
  local code
  if protocol.ErrorCodes[err.code] then
    code = string.format("code_name = %s,", protocol.ErrorCodes[err.code])
  else
    code = string.format("code_name = unknown, code = %s,", err.code)
  end

  local message_parts = {"RPC[Error]", code}
  if err.message then
    table.insert(message_parts, "message =")
    table.insert(message_parts, string.format("%q", err.message))
  end
  if err.data then
    table.insert(message_parts, "data =")
    table.insert(message_parts, vim.inspect(err.data))
  end
  return table.concat(message_parts, ' ')
end

--- Creates an RPC response object/table.
---
---@param code RPC error code defined in `vim.lsp.protocol.ErrorCodes`
---@param message (optional) arbitrary message to send to server
---@param data (optional) arbitrary data to send to server
local function rpc_response_error(code, message, data)
  -- TODO should this error or just pick a sane error (like InternalError)?
  local code_name = assert(protocol.ErrorCodes[code], 'Invalid RPC error code')
  return setmetatable({
    code = code;
    message = message or code_name;
    data = data;
  }, {
    __tostring = format_rpc_error;
  })
end

local default_dispatchers = {}

---@private
--- Default dispatcher for notifications sent to an LSP server.
---
---@param method (string) The invoked LSP method
---@param params (table): Parameters for the invoked LSP method
function default_dispatchers.notification(method, params)
  local _ = log.debug() and log.debug('notification', method, params)
end
---@private
--- Default dispatcher for requests sent to an LSP server.
---
---@param method (string) The invoked LSP method
---@param params (table): Parameters for the invoked LSP method
---@returns `nil` and `vim.lsp.protocol.ErrorCodes.MethodNotFound`.
function default_dispatchers.server_request(method, params)
  local _ = log.debug() and log.debug('server_request', method, params)
  return nil, rpc_response_error(protocol.ErrorCodes.MethodNotFound)
end
---@private
--- Default dispatcher for when a client exits.
---
---@param code (number): Exit code
---@param signal (number): Number describing the signal used to terminate (if
---any)
function default_dispatchers.on_exit(code, signal)
  local _ = log.info() and log.info("client_exit", { code = code, signal = signal })
end
---@private
--- Default dispatcher for client errors.
---
---@param code (number): Error code
---@param err (any): Details about the error
---any)
function default_dispatchers.on_error(code, err)
  local _ = log.error() and log.error('client_error:', client_errors[code], err)
end

--- Starts an LSP server process and create an LSP RPC client object to
--- interact with it.
---
---@param cmd (string) Command to start the LSP server.
---@param cmd_args (table) List of additional string arguments to pass to {cmd}.
---@param dispatchers (table, optional) Dispatchers for LSP message types. Valid
---dispatcher names are:
--- - `"notification"`
--- - `"server_request"`
--- - `"on_error"`
--- - `"on_exit"`
---@param extra_spawn_params (table, optional) Additional context for the LSP
--- server process. May contain:
--- - {cwd} (string) Working directory for the LSP server process
--- - {env} (table) Additional environment variables for LSP server process
---@returns Client RPC object.
---
---@returns Methods:
--- - `notify()` |vim.lsp.rpc.notify()|
--- - `request()` |vim.lsp.rpc.request()|
---
---@returns Members:
--- - {pid} (number) The LSP server's PID.
--- - {handle} A handle for low-level interaction with the LSP server process
---   |vim.loop|.
local function start(cmd, cmd_args, dispatchers, extra_spawn_params)
  local _ = log.info() and log.info("Starting RPC client", {cmd = cmd, args = cmd_args, extra = extra_spawn_params})
  validate {
    cmd = { cmd, 's' };
    cmd_args = { cmd_args, 't' };
    dispatchers = { dispatchers, 't', true };
  }

  if extra_spawn_params and extra_spawn_params.cwd then
      assert(is_dir(extra_spawn_params.cwd), "cwd must be a directory")
  elseif not (vim.fn.executable(cmd) == 1) then
      error(string.format("The given command %q is not executable.", cmd))
  end
  if dispatchers then
    local user_dispatchers = dispatchers
    dispatchers = {}
    for dispatch_name, default_dispatch in pairs(default_dispatchers) do
      local user_dispatcher = user_dispatchers[dispatch_name]
      if user_dispatcher then
        if type(user_dispatcher) ~= 'function' then
          error(string.format("dispatcher.%s must be a function", dispatch_name))
        end
        -- server_request is wrapped elsewhere.
        if not (dispatch_name == 'server_request'
          or dispatch_name == 'on_exit') -- TODO this blocks the loop exiting for some reason.
        then
          user_dispatcher = schedule_wrap(user_dispatcher)
        end
        dispatchers[dispatch_name] = user_dispatcher
      else
        dispatchers[dispatch_name] = default_dispatch
      end
    end
  else
    dispatchers = default_dispatchers
  end

  local stdin = uv.new_pipe(false)
  local stdout = uv.new_pipe(false)
  local stderr = uv.new_pipe(false)

  local message_index = 0
  local message_callbacks = {}
  local notify_reply_callbacks = {}

  local handle, pid
  do
    ---@private
    --- Callback for |vim.loop.spawn()| Closes all streams and runs the `on_exit` dispatcher.
    ---@param code (number) Exit code
    ---@param signal (number) Signal that was used to terminate (if any)
    local function onexit(code, signal)
      stdin:close()
      stdout:close()
      stderr:close()
      handle:close()
      -- Make sure that message_callbacks/notify_reply_callbacks can be gc'd.
      message_callbacks = nil
      notify_reply_callbacks = nil
      dispatchers.on_exit(code, signal)
    end
    local spawn_params = {
      args = cmd_args;
      stdio = {stdin, stdout, stderr};
    }
    if extra_spawn_params then
      spawn_params.cwd = extra_spawn_params.cwd
      spawn_params.env = env_merge(extra_spawn_params.env)
    end
    handle, pid = uv.spawn(cmd, spawn_params, onexit)
    if handle == nil then
      error(string.format("start `%s` failed: %s", cmd, pid))
    end
  end

  ---@private
  --- Encodes {payload} into a JSON-RPC message and sends it to the remote
  --- process.
  ---
  ---@param payload table
  ---@returns true if the payload could be scheduled, false if the main event-loop is in the process of closing.
  local function encode_and_send(payload)
    local _ = log.debug() and log.debug("rpc.send", payload)
    if handle == nil or handle:is_closing() then return false end
    local encoded = vim.json.encode(payload)
    stdin: