feat: add single file mode (#1385)

* This adds a "single file mode" option for each language server
* Currently, if a root is not detected, a new language server is started
  for each file opened.
* Root directory is set to `nil` in start_client. Some servers will
  refuse to start, or otherwise panic. This is opt-in per server.
* Some servers, such as rust-analyzer, explicitly have a "single file
  mode", we will not support that until it is officially part of the LSP
  specification

Co-authored-by: Peter Lithammer <peter.lithammer@gmail.com>

1 files changed, 34 insertions, 15 deletions

diff --git a/lua/lspconfig/configs.lua b/lua/lspconfig/configs.lua
index 2f4cd0d7..f69e2673 100644
--- a/lua/lspconfig/configs.lua
+++ b/lua/lspconfig/configs.lua
@@ -78,22 +78,29 @@ function configs.__newindex(t, config_name, config_def)
 
     function M.launch()
       local root_dir = get_root_dir(api.nvim_buf_get_name(0), api.nvim_get_current_buf())
-      if not root_dir then
-        vim.notify(string.format('Launching %s failed: matching root directory not detected.', config_name))
-        return
-      end
-      api.nvim_command(
-        string.format(
-          "autocmd %s unsilent lua require'lspconfig'[%q].manager.try_add_wrapper()",
-          'BufReadPost ' .. root_dir .. '/*',
-          config.name
+      if root_dir then
+        api.nvim_command(
+          string.format(
+            "autocmd %s unsilent lua require'lspconfig'[%q].manager.try_add_wrapper()",
+            'BufReadPost ' .. root_dir .. '/*',
+            config.name
+          )
         )
-      )
-      for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
-        local buf_dir = api.nvim_buf_get_name(bufnr)
-        if buf_dir:sub(1, root_dir:len()) == root_dir then
-          M.manager.try_add_wrapper(bufnr)
+        for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
+          local buf_dir = api.nvim_buf_get_name(bufnr)
+          if buf_dir:sub(1, root_dir:len()) == root_dir then
+            M.manager.try_add_wrapper(bufnr)
+          end
         end
+      elseif config.single_file_support then
+        -- This allows on_new_config to use the parent directory of the file
+        -- Effectively this is the root from lspconfig's perspective, as we use
+        -- this to attach additional files in the same parent folder to the same server.
+        -- We just no longer send rootDirectory or workspaceFolders during initialization.
+        local pseudo_root = util.path.dirname(api.nvim_buf_get_name(0))
+        M.manager.add(pseudo_root, true)
+      else
+        vim.notify(string.format('Autostart for %s failed: matching root directory not detected.', config_name))
       end
     end
 
@@ -182,11 +189,23 @@ function configs.__newindex(t, config_name, config_def)
 
     function manager.try_add(bufnr)
       bufnr = bufnr or api.nvim_get_current_buf()
+
       if vim.api.nvim_buf_get_option(bufnr, 'buftype') == 'nofile' then
         return
       end
+
+      local id
       local root_dir = get_root_dir(api.nvim_buf_get_name(bufnr), bufnr)
-      local id = manager.add(root_dir)
+
+      if root_dir then
+        id = manager.add(root_dir, false)
+      elseif config.single_file_support then
+        local pseudo_root = util.path.dirname(api.nvim_buf_get_name(0))
+        id = manager.add(pseudo_root, true)
+      else
+        vim.notify(string.format('Autostart for %s failed: matching root directory not detected.', config_name))
+      end
+
       if id then
         lsp.buf_attach_client(bufnr, id)
       end