refactor(lsp): move client code to a regular Lua class

Problem:
  The LSP client code is implemented as a complicated closure-class
  (class defined in a single function).

Solution:
  Move LSP client code to a more conventional Lua class and move to a
  separate file.

1 files changed, 663 insertions, 0 deletions

diff --git a/runtime/lua/vim/lsp/client.lua b/runtime/lua/vim/lsp/client.lua
new file mode 100644
index 0000000000..2daf564f63
--- /dev/null
+++ b/runtime/lua/vim/lsp/client.lua
@@ -0,0 +1,663 @@
+local uv = vim.uv
+local api = vim.api
+local lsp = vim.lsp
+local log = lsp.log
+local ms = lsp.protocol.Methods
+local changetracking = lsp._changetracking
+
+--- @class lsp.Client.Progress: vim.Ringbuf<{token: integer|string, value: any}>
+--- @field pending table<lsp.ProgressToken,lsp.LSPAny>
+
+--- @class lsp.Client
+---
+--- The id allocated to the client.
+--- @field id integer
+---
+--- If a name is specified on creation, that will be used. Otherwise it is just
+--- the client id. This is used for logs and messages.
+--- @field name string
+---
+--- RPC client object, for low level interaction with the client.
+--- See |vim.lsp.rpc.start()|.
+--- @field rpc vim.lsp.rpc.PublicClient
+---
+--- The encoding used for communicating with the server. You can modify this in
+--- the `config`'s `on_init` method before text is sent to the server.
+--- @field offset_encoding string
+---
+--- The handlers used by the client as described in |lsp-handler|.
+--- @field handlers table<string,lsp.Handler>
+---
+--- The current pending requests in flight to the server. Entries are key-value
+--- pairs with the key being the request ID while the value is a table with
+--- `type`, `bufnr`, and `method` key-value pairs. `type` is either "pending"
+--- for an active request, or "cancel" for a cancel request. It will be
+--- "complete" ephemerally while executing |LspRequest| autocmds when replies
+--- are received from the server.
+--- @field requests table<integer,{ type: string, bufnr: integer, method: string}>
+---
+--- copy of the table that was passed by the user
+--- to |vim.lsp.start_client()|.
+--- @field config lsp.ClientConfig
+---
+--- Response from the server sent on
+--- initialize` describing the server's capabilities.
+--- @field server_capabilities lsp.ServerCapabilities
+---
+--- A ring buffer (|vim.ringbuf()|) containing progress messages
+--- sent by the server.
+--- @field progress lsp.Client.Progress
+---
+--- @field initialized true?
+--- @field workspace_folders lsp.WorkspaceFolder[]?
+--- @field attached_buffers table<integer,true>
+--- @field commands table<string,function>
+--- @field private _log_prefix string
+--- Track this so that we can escalate automatically if we've already tried a
+--- graceful shutdown
+--- @field private _graceful_shutdown_failed true?
+---
+--- @field dynamic_capabilities lsp.DynamicCapabilities
+---
+--- Sends a request to the server.
+--- This is a thin wrapper around {client.rpc.request} with some additional
+--- checking.
+--- If {handler} is not specified,  If one is not found there, then an error
+--- will occur. Returns: {status}, {[client_id]}. {status} is a boolean
+--- indicating if the notification was successful. If it is `false`, then it
+--- will always be `false` (the client has shutdown).
+--- If {status} is `true`, the function returns {request_id} as the second
+--- result. You can use this with `client.cancel_request(request_id)` to cancel
+--- the request.
+--- @field request fun(method: string, params: table?, handler: lsp.Handler?, bufnr: integer): boolean, integer?
+---
+--- Sends a request to the server and synchronously waits for the response.
+--- This is a wrapper around {client.request}
+--- Returns: { err=err, result=result }, a dictionary, where `err` and `result`
+--- come from the |lsp-handler|. On timeout, cancel or error, returns `(nil,
+--- err)` where `err` is a string describing the failure reason. If the request
+--- was unsuccessful returns `nil`.
+--- @field request_sync fun(method: string, params: table?, timeout_ms: integer?, bufnr: integer): {err: lsp.ResponseError|nil, result:any}|nil, string|nil err # a dictionary, where
+---
+--- Sends a notification to an LSP server.
+--- Returns: a boolean to indicate if the notification was successful. If
+--- it is false, then it will always be false (the client has shutdown).
+--- @field notify fun(method: string, params: table?): boolean
+---
+--- Cancels a request with a given request id.
+--- Returns: same as `notify()`.
+--- @field cancel_request fun(id: integer): boolean
+---
+--- Stops a client, optionally with force.
+--- By default, it will just ask the server to shutdown without force.
+--- If you request to stop a client which has previously been requested to
+--- shutdown, it will automatically escalate and force shutdown.
+--- @field stop fun(force?: boolean)
+---
+--- Runs the on_attach function from the client's config if it was defined.
+--- Useful for buffer-local setup.
+--- @field on_attach fun(bufnr: integer)
+---
+--- Checks if a client supports a given method.
+--- Always returns true for unknown off-spec methods.
+--- [opts] is a optional `{bufnr?: integer}` table.
+--- Some language server capabilities can be file specific.
+--- @field supports_method fun(method: string, opts?: {bufnr: integer?}): boolean
+---
+--- Checks whether a client is stopped.
+--- Returns: true if the client is fully stopped.
+--- @field is_stopped fun(): boolean
+local Client = {}
+Client.__index = Client
+
+--- @param cls table
+--- @param meth any
+--- @return function
+local function method_wrapper(cls, meth)
+  return function(...)
+    return meth(cls, ...)
+  end
+end
+
+--- @package
+--- @param id integer
+--- @param rpc vim.lsp.rpc.PublicClient
+--- @param handlers table<string,lsp.Handler>
+--- @param offset_encoding string
+--- @param config lsp.ClientConfig
+--- @return lsp.Client
+function Client.new(id, rpc, handlers, offset_encoding, config)
+  local name = config.name
+
+  --- @class lsp.Client
+  local self = {
+    id = id,
+    config = config,
+    handlers = handlers,
+    rpc = rpc,
+    offset_encoding = offset_encoding,
+    name = name,
+    _log_prefix = string.format('LSP[%s]', name),
+    requests = {},
+    commands = config.commands or {},
+    attached_buffers = {},
+    server_capabilities = {},
+    dynamic_capabilities = vim.lsp._dynamic.new(id),
+
+    --- Contains $/progress report messages.
+    --- They have the format {token: integer|string, value: any}
+    --- For "work done progress", value will be one of:
+    --- - lsp.WorkDoneProgressBegin,
+    --- - lsp.WorkDoneProgressReport (extended with title from Begin)
+    --- - lsp.WorkDoneProgressEnd    (extended with title from Begin)
+    progress = vim.ringbuf(50) --[[@as lsp.Client.Progress]],
+
+    --- @deprecated use client.progress instead
+    messages = { name = name, messages = {}, progress = {}, status = {} },
+  }
+
+  self.request = method_wrapper(self, Client._request)
+  self.request_sync = method_wrapper(self, Client._request_sync)
+  self.notify = method_wrapper(self, Client._notify)
+  self.cancel_request = method_wrapper(self, Client._cancel_request)
+  self.stop = method_wrapper(self, Client._stop)
+  self.is_stopped = method_wrapper(self, Client._is_stopped)
+  self.on_attach = method_wrapper(self, Client._on_attach)
+  self.supports_method = method_wrapper(self, Client._supports_method)
+
+  ---@type table<string|integer, string> title of unfinished progress sequences by token
+  self.progress.pending = {}
+
+  return setmetatable(self, Client)
+end
+
+--- @private
+--- @param cb fun()
+function Client:initialize(cb)
+  local valid_traces = {
+    off = 'off',
+    messages = 'messages',
+    verbose = 'verbose',
+  }
+
+  local config = self.config
+
+  local workspace_folders --- @type lsp.WorkspaceFolder[]?
+  local root_uri --- @type string?
+  local root_path --- @type string?
+  if config.workspace_folders or config.root_dir then
+    if config.root_dir and not config.workspace_folders then
+      workspace_folders = {
+        {
+          uri = vim.uri_from_fname(config.root_dir),
+          name = string.format('%s', config.root_dir),
+        },
+      }
+    else
+      workspace_folders = config.workspace_folders
+    end
+    root_uri = workspace_folders[1].uri
+    root_path = vim.uri_to_fname(root_uri)
+  else
+    workspace_folders = nil
+    root_uri = nil
+    root_path = nil
+  end
+
+  local initialize_params = {
+    -- The process Id of the parent process that started the server. Is null if
+    -- the process has not been started by another process.  If the parent
+    -- process is not alive then the server should exit (see exit notification)
+    -- its process.
+    processId = uv.os_getpid(),
+    -- Information about the client
+    -- since 3.15.0
+    clientInfo = {
+      name = 'Neovim',
+      version = tostring(vim.version()),
+    },
+    -- The rootPath of the workspace. Is null if no folder is open.
+    --
+    -- @deprecated in favour of rootUri.
+    rootPath = root_path or vim.NIL,
+    -- The rootUri of the workspace. Is null if no folder is open. If both
+    -- `rootPath` and `rootUri` are set `rootUri` wins.
+    rootUri = root_uri or vim.NIL,
+    -- The workspace folders configured in the client when the server starts.
+    -- This property is only available if the client supports workspace folders.
+    -- It can be `null` if the client supports workspace folders but none are
+    -- configured.
+    workspaceFolders = workspace_folders or vim.NIL,
+    -- User provided initialization options.
+    initializationOptions = config.init_options,
+    -- The capabilities provided by the client (editor or tool)
+    capabilities = config.capabilities,
+    -- The initial trace setting. If omitted trace is disabled ("off").
+    -- trace = "off" | "messages" | "verbose";
+    trace = valid_traces[config.trace] or 'off',
+  }
+  if config.before_init then
+    --- @type boolean, string?
+    local status, err = pcall(config.before_init, initialize_params, config)
+    if not status then
+      self:write_error(lsp.client_errors.BEFORE_INIT_CALLBACK_ERROR, err)
+    end
+  end
+
+  if log.trace() then
+    log.trace(self._log_prefix, 'initialize_params', initialize_params)
+  end
+
+  local rpc = self.rpc
+
+  rpc.request('initialize', initialize_params, function(init_err, result)
+    assert(not init_err, tostring(init_err))
+    assert(result, 'server sent empty result')
+    rpc.notify('initialized', vim.empty_dict())
+    self.initialized = true
+    self.workspace_folders = workspace_folders
+
+    -- These are the cleaned up capabilities we use for dynamically deciding
+    -- when to send certain events to clients.
+    self.server_capabilities =
+      assert(result.capabilities, "initialize result doesn't contain capabilities")
+    self.server_capabilities = assert(lsp.protocol.resolve_capabilities(self.server_capabilities))
+
+    if self.server_capabilities.positionEncoding then
+      self.offset_encoding = self.server_capabilities.positionEncoding
+    end
+
+    if next(config.settings) then
+      self:_notify(ms.workspace_didChangeConfiguration, { settings = config.settings })
+    end
+
+    if config.on_init then
+      --- @type boolean, string?
+      local status, err = pcall(config.on_init, self, result)
+      if not status then
+        self:write_error(lsp.client_errors.ON_INIT_CALLBACK_ERROR, err)
+      end
+    end
+    if log.info() then
+      log.info(
+        self._log_prefix,
+        'server_capabilities',
+        { server_capabilities = self.server_capabilities }
+      )
+    end
+
+    cb()
+  end)
+end
+
+--- @private
+--- Returns the handler associated with an LSP method.
+--- Returns the default handler if the user hasn't set a custom one.
+---
+--- @param method (string) LSP method name
+--- @return lsp.Handler|nil handler for the given method, if defined, or the default from |vim.lsp.handlers|
+function Client:_resolve_handler(method)
+  return self.handlers[method] or lsp.handlers[method]
+end
+
+--- Returns the buffer number for the given {bufnr}.
+---
+--- @param bufnr (integer|nil) Buffer number to resolve. Defaults to current buffer
+--- @return integer bufnr
+local function resolve_bufnr(bufnr)
+  vim.validate({ bufnr = { bufnr, 'n', true } })
+  if bufnr == nil or bufnr == 0 then
+    return api.nvim_get_current_buf()
+  end
+  return bufnr
+end
+
+--- @private
+--- Sends a request to the server.
+---
+--- This is a thin wrapper around {client.rpc.request} with some additional
+--- checks for capabilities and handler availability.
+---
+--- @param method string LSP method name.
+--- @param params table|nil LSP request params.
+--- @param handler lsp.Handler|nil Response |lsp-handler| for this method.
+--- @param bufnr integer Buffer handle (0 for current).
+--- @return boolean status, integer|nil request_id {status} is a bool indicating
+--- whether the request was successful. If it is `false`, then it will
+--- always be `false` (the client has shutdown). If it was
+--- successful, then it will return {request_id} as the
+--- second result. You can use this with `client.cancel_request(request_id)`
+--- to cancel the-request.
+--- @see |vim.lsp.buf_request_all()|
+function Client:_request(method, params, handler, bufnr)
+  if not handler then
+    handler = assert(
+      self:_resolve_handler(method),
+      string.format('not found: %q request handler for client %q.', method, self.name)
+    )
+  end
+  -- Ensure pending didChange notifications are sent so that the server doesn't operate on a stale state
+  changetracking.flush(self, bufnr)
+  local version = lsp.util.buf_versions[bufnr]
+  bufnr = resolve_bufnr(bufnr)
+  if log.debug() then
+    log.debug(self._log_prefix, 'client.request', self.id, method, params, handler, bufnr)
+  end
+  local success, request_id = self.rpc.request(method, params, function(err, result)
+    local context = {
+      method = method,
+      client_id = self.id,
+      bufnr = bufnr,
+      params = params,
+      version = version,
+    }
+    handler(err, result, context)
+  end, function(request_id)
+    local request = self.requests[request_id]
+    request.type = 'complete'
+    api.nvim_exec_autocmds('LspRequest', {
+      buffer = api.nvim_buf_is_valid(bufnr) and bufnr or nil,
+      modeline = false,
+      data = { client_id = self.id, request_id = request_id, request = request },
+    })
+    self.requests[request_id] = nil
+  end)
+
+  if success and request_id then
+    local request = { type = 'pending', bufnr = bufnr, method = method }
+    self.requests[request_id] = request
+    api.nvim_exec_autocmds('LspRequest', {
+      buffer = bufnr,
+      modeline = false,
+      data = { client_id = self.id, request_id = request_id, request = request },
+    })
+  end
+
+  return success, request_id
+end
+
+-- TODO(lewis6991): duplicated from lsp.lua
+local wait_result_reason = { [-1] = 'timeout', [-2] = 'interrupted', [-3] = 'error' }
+
+-- TODO(lewis6991): duplicated from lsp.lua
+--- Concatenates and writes a list of strings to the Vim error buffer.
+---
+---@param ... string List to write to the buffer
+local function err_message(...)
+  api.nvim_err_writeln(table.concat(vim.tbl_flatten({ ... })))
+  api.nvim_command('redraw')
+end
+
+--- @private
+--- Sends a request to the server and synchronously waits for the response.
+---
+--- This is a wrapper around {client.request}
+---
+--- @param method (string) LSP method name.
+--- @param params (table) LSP request params.
+--- @param timeout_ms (integer|nil) Maximum time in milliseconds to wait for
+---                                a result. Defaults to 1000
+--- @param bufnr (integer) Buffer handle (0 for current).
+--- @return {err: lsp.ResponseError|nil, result:any}|nil, string|nil err # a dictionary, where
+--- `err` and `result` come from the |lsp-handler|.
+--- On timeout, cancel or error, returns `(nil, err)` where `err` is a
+--- string describing the failure reason. If the request was unsuccessful
+--- returns `nil`.
+--- @see |vim.lsp.buf_request_sync()|
+function Client:_request_sync(method, params, timeout_ms, bufnr)
+  local request_result = nil
+  local function _sync_handler(err, result)
+    request_result = { err = err, result = result }
+  end
+
+  local success, request_id = self:_request(method, params, _sync_handler, bufnr)
+  if not success then
+    return nil
+  end
+
+  local wait_result, reason = vim.wait(timeout_ms or 1000, function()
+    return request_result ~= nil
+  end, 10)
+
+  if not wait_result then
+    if request_id then
+      self:_cancel_request(request_id)
+    end
+    return nil, wait_result_reason[reason]
+  end
+  return request_result
+end
+
+--- @private
+--- Sends a notification to an LSP server.
+---
+--- @param method string LSP method name.
+--- @param params table|nil LSP request params.
+--- @return boolean status true if the notification was successful.
+--- If it is false, then it will always be false
+--- (the client has shutdown).
+function Client:_notify(method, params)
+  if method ~= ms.textDocument_didChange then
+    changetracking.flush(self)
+  end
+
+  local client_active = self.rpc.notify(method, params)
+
+  if client_active then
+    vim.schedule(function()
+      api.nvim_exec_autocmds('LspNotify', {
+        modeline = false,
+        data = {
+          client_id = self.id,
+          method = method,
+          params = params,
+        },
+      })
+    end)
+  end
+
+  return client_active
+end
+
+--- @private
+--- Cancels a request with a given request id.
+---
+--- @param id (integer) id of request to cancel
+--- @return boolean status true if notification was successful. false otherwise
+--- @see |vim.lsp.client.notify()|
+function Client:_cancel_request(id)
+  vim.validate({ id = { id, 'n' } })
+  local request = self.requests[id]
+  if request and request.type == 'pending' then
+    request.type = 'cancel'
+    api.nvim_exec_autocmds('LspRequest', {
+      buffer = request.bufnr,
+      modeline = false,
+      data = { client_id = self.id, request_id = id, request = request },
+    })
+  end
+  return self.rpc.notify(ms.dollar_cancelRequest, { id = id })
+end
+
+--- @nodoc
+--- Stops a client, optionally with force.
+---
+--- By default, it will just ask the - server to shutdown without force. If
+--- you request to stop a client which has previously been requested to
+--- shutdown, it will automatically escalate and force shutdown.
+---
+--- @param force boolean|nil
+function Client:_stop(force)
+  local rpc = self.rpc
+
+  if rpc.is_closing() then
+    return
+  end
+
+  if force or not self.initialized or self._graceful_shutdown_failed then
+    rpc.terminate()
+    return
+  end
+
+  -- Sending a signal after a process has exited is acceptable.
+  rpc.request(ms.shutdown, nil, function(err, _)
+    if err == nil then
+      rpc.notify(ms.exit)
+    else
+      -- If there was an error in the shutdown request, then term to be safe.
+      rpc.terminate()
+      self._graceful_shutdown_failed = true
+    end
+  end)
+end
+
+--- @private
+--- Checks whether a client is stopped.
+---
+--- @return boolean # true if client is stopped or in the process of being
+--- stopped; false otherwise
+function Client:_is_stopped()
+  return self.rpc.is_closing()
+end
+
+--- @private
+--- Execute a lsp command, either via client command function (if available)
+--- or via workspace/executeCommand (if supported by the server)
+---
+--- @param command lsp.Command
+--- @param context? {bufnr: integer}
+--- @param handler? lsp.Handler only called if a server command
+function Client:_exec_cmd(command, context, handler)
+  context = vim.deepcopy(context or {}, true) --[[@as lsp.HandlerContext]]
+  context.bufnr = context.bufnr or api.nvim_get_current_buf()
+  context.client_id = self.id
+  local cmdname = command.command
+  local fn = self.commands[cmdname] or lsp.commands[cmdname]
+  if fn then
+    fn(command, context)
+    return
+  end
+
+  local command_provider = self.server_capabilities.executeCommandProvider
+  local commands = type(command_provider) == 'table' and command_provider.commands or {}
+  if not vim.list_contains(commands, cmdname) then
+    vim.notify_once(
+      string.format(
+        'Language server `%s` does not support command `%s`. This command may require a client extension.',
+        self.name,
+        cmdname
+      ),
+      vim.log.levels.WARN
+    )
+    return
+  end
+  -- Not using command directly to exclude extra properties,
+  -- see https://github.com/python-lsp/python-lsp-server/issues/146
+  local params = {
+    command = command.command,
+    arguments = command.arguments,
+  }
+  self.request(ms.workspace_executeCommand, params, handler, context.bufnr)
+end
+
+--- @package
+--- Default handler for the 'textDocument/didOpen' LSP notification.
+---
+--- @param bufnr integer Number of the buffer, or 0 for current
+function Client:_text_document_did_open_handler(bufnr)
+  changetracking.init(self, bufnr)
+  if not vim.tbl_get(self.server_capabilities, 'textDocumentSync', 'openClose') then
+    return
+  end
+  if not api.nvim_buf_is_loaded(bufnr) then
+    return
+  end
+  local filetype = vim.bo[bufnr].filetype
+
+  local params = {
+    textDocument = {
+      version = 0,
+      uri = vim.uri_from_bufnr(bufnr),
+      languageId = self.config.get_language_id(bufnr, filetype),
+      text = lsp._buf_get_full_text(bufnr),
+    },
+  }
+  self.notify(ms.textDocument_didOpen, params)
+  lsp.util.buf_versions[bufnr] = params.textDocument.version
+
+  -- Next chance we get, we should re-do the diagnostics
+  vim.schedule(function()
+    -- Protect against a race where the buffer disappears
+    -- between `did_open_handler` and the scheduled function firing.
+    if api.nvim_buf_is_valid(bufnr) then
+      local namespace = vim.lsp.diagnostic.get_namespace(self.id)
+      vim.diagnostic.show(namespace, bufnr)
+    end
+  end)
+end
+
+--- @private
+--- Runs the on_attach function from the client's config if it was defined.
+--- @param bufnr integer Buffer number
+function Client:_on_attach(bufnr)
+  self:_text_document_did_open_handler(bufnr)
+
+  lsp._set_defaults(self, bufnr)
+
+  api.nvim_exec_autocmds('LspAttach', {
+    buffer = bufnr,
+    modeline = false,
+    data = { client_id = self.id },
+  })
+
+  if self.config.on_attach then
+    --- @type boolean, string?
+    local status, err = pcall(self.config.on_attach, self, bufnr)
+    if not status then
+      self:write_error(lsp.client_errors.ON_ATTACH_ERROR, err)
+    end
+  end
+
+  -- schedule the initialization of semantic tokens to give the above
+  -- on_attach and LspAttach callbacks the ability to schedule wrap the
+  -- opt-out (deleting the semanticTokensProvider from capabilities)
+  vim.schedule(function()
+    if vim.tbl_get(self.server_capabilities, 'semanticTokensProvider', 'full') then
+      lsp.semantic_tokens.start(bufnr, self.id)
+    end
+  end)
+
+  self.attached_buffers[bufnr] = true
+end
+
+--- @private
+--- Logs the given error to the LSP log and to the error buffer.
+--- @param code integer Error code
+--- @param err any Error arguments
+function Client:write_error(code, err)
+  if log.error() then
+    log.error(self._log_prefix, 'on_error', { code = lsp.client_errors[code], err = err })
+  end
+  err_message(self._log_prefix, ': Error ', lsp.client_errors[code], ': ', vim.inspect(err))
+end
+
+--- @param method string
+--- @param opts? {bufnr: integer?}
+function Client:_supports_method(method, opts)
+  opts = opts or {}
+  local required_capability = lsp._request_name_to_capability[method]
+  -- if we don't know about the method, assume that the client supports it.
+  if not required_capability then
+    return true
+  end
+  if vim.tbl_get(self.server_capabilities, unpack(required_capability)) then
+    return true
+  else
+    if self.dynamic_capabilities:supports_registration(method) then
+      return self.dynamic_capabilities:supports(method, opts)
+    end
+    return false
+  end
+end
+
+return Client