[docgen] Update CONFIG.md

skip-checks: true

1 files changed, 12 insertions, 0 deletions

diff --git a/CONFIG.md b/CONFIG.md
index bc3f27f1..1bfd3286 100644
--- a/CONFIG.md
+++ b/CONFIG.md
@@ -1278,6 +1278,18 @@ require'lspconfig'.dotls.setup{}
 https://github.com/mattn/efm-langserver
 
 General purpose Language Server that can use specified error message format generated from specified command.
+    
+Note: In order for neovim's built-in language server client to send the appropriate `languageId` to EFM, **you must
+specify `filetypes` in your call to `setup{}`**. Otherwise `lspconfig` will launch EFM on the `BufEnter` instead
+of the `FileType` autocommand, and the `filetype` variable used to populate the `languageId` will not yet be set.
+ 
+```lua
+require('lspconfig')['efm'].setup{
+  settings = ..., -- You must populate this according to the EFM readme
+  filetypes = { 'python','cpp','lua' }
+}
+```
+