1 files changed, 72 insertions, 0 deletions
diff --git a/lua/lspconfig/elmls.lua b/lua/lspconfig/elmls.lua
new file mode 100644
index 00000000..c35824c4
--- /dev/null
+++ b/lua/lspconfig/elmls.lua
@@ -0,0 +1,72 @@
+local configs = require 'lspconfig/configs'
+local util = require 'lspconfig/util'
+local lsp = vim.lsp
+local api = vim.api
+
+local server_name = "elmls"
+local bin_name = "elm-language-server"
+
+local installer = util.npm_installer {
+  server_name = server_name;
+  packages = { "elm", "elm-test", "elm-format", "@elm-tooling/elm-language-server" };
+  binaries = {bin_name, "elm", "elm-format", "elm-test"};
+}
+
+local default_capabilities = lsp.protocol.make_client_capabilities()
+default_capabilities.offsetEncoding = {"utf-8", "utf-16"}
+local elm_root_pattern = util.root_pattern("elm.json")
+
+configs[server_name] = {
+  default_config = {
+    cmd = {bin_name};
+    -- TODO(ashkan) if we comment this out, it will allow elmls to operate on elm.json. It seems like it could do that, but no other editor allows it right now.
+    filetypes = {"elm"};
+    root_dir = function(fname)
+      local filetype = api.nvim_buf_get_option(0, 'filetype')
+      if filetype == 'elm' or (filetype == 'json' and fname:match("elm%.json$")) then
+        return elm_root_pattern(fname)
+      end
+    end;
+    init_options = {
+      elmPath = "elm",
+      elmFormatPath = "elm-format",
+      elmTestPath = "elm-test",
+      elmAnalyseTrigger = "change",
+    };
+  };
+  on_new_config = function(new_config)
+    local install_info = installer.info()
+    if install_info.is_installed then
+      if type(new_config.cmd) == 'table' then
+        -- Try to preserve any additional args from upstream changes.
+        new_config.cmd[1] = install_info.binaries[bin_name]
+      else
+        new_config.cmd = {install_info.binaries[bin_name]}
+      end
+      new_config.init_options = util.tbl_deep_extend('force', new_config.init_options, {
+        elmPath = install_info.binaries["elm"];
+        elmFormatPath = install_info.binaries["elm-format"];
+        elmTestPath = install_info.binaries["elm-test"];
+      })
+    end
+  end;
+  docs = {
+    package_json = "https://raw.githubusercontent.com/elm-tooling/elm-language-client-vscode/master/package.json";
+    description = [[
+https://github.com/elm-tooling/elm-language-server#installation
+
+If you don't want to use Nvim to install it, then you can use:
+```sh
+npm install -g elm elm-test elm-format @elm-tooling/elm-language-server
+```
+]];
+    default_config = {
+      root_dir = [[root_pattern("elm.json")]];
+    };
+  };
+}
+
+configs[server_name].install = installer.install
+configs[server_name].install_info = installer.info
+-- vim:et ts=2 sw=2
+