1 files changed, 26 insertions, 0 deletions
diff --git a/.config/nvim/lsp/expert.lua b/.config/nvim/lsp/expert.lua
new file mode 100644
index 0000000..f7146a6
--- /dev/null
+++ b/.config/nvim/lsp/expert.lua
@@ -0,0 +1,26 @@
+---@brief
+---
+--- https://github.com/elixir-lang/expert
+---
+--- Expert is the official language server implementation for the Elixir programming language.
+---
+--- 'root_dir' is chosen like this: if two or more directories containing `mix.exs` were found when
+--- searching directories upward, the second one (higher up) is chosen, with the assumption that it
+--- is the root of an umbrella app. Otherwise the directory containing the single mix.exs that was
+--- found is chosen.
+
+---@type vim.lsp.Config
+return {
+  filetypes = { 'elixir', 'eelixir', 'heex', 'surface' },
+  cmd = { 'expert' },
+  root_dir = function(bufnr, on_dir)
+    local fname = vim.api.nvim_buf_get_name(bufnr)
+    --- Elixir workspaces may have multiple `mix.exs` files, for an "umbrella" layout or monorepo.
+    --- So we specify `limit=2` and treat the highest one (if any) as the root of an umbrella app.
+    local matches = vim.fs.find({ 'mix.exs' }, { upward = true, limit = 2, path = fname })
+    local child_or_root_path, maybe_umbrella_path = unpack(matches)
+    local root_dir = vim.fs.dirname(maybe_umbrella_path or child_or_root_path)
+
+    on_dir(root_dir)
+  end,
+}