feat(lsp): support hostname in rpc.connect #30238

Updated the `rpc.connect` function to support connecting to LSP servers
using hostnames, not just IP addresses. This change includes updates to
the documentation and additional test cases to verify the new
functionality.

- Modified `connect` function to resolve hostnames.
- Updated documentation to reflect the change.
- Added test case for connecting using hostname.

Added a TCP echo server utility function to the LSP test suite. This
server echoes the first message it receives and is used in tests to
verify LSP server connections via both IP address and hostname.
Refactored existing tests to use the new utility function.

1 files changed, 24 insertions, 16 deletions

diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index ff042424f9..1347ea9745 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -33,6 +33,7 @@ local create_server_definition = t_lsp.create_server_definition
 local fake_lsp_code = t_lsp.fake_lsp_code
 local fake_lsp_logfile = t_lsp.fake_lsp_logfile
 local test_rpc_server = t_lsp.test_rpc_server
+local create_tcp_echo_server = t_lsp.create_tcp_echo_server
 
 local function get_buf_option(name, bufnr)
   bufnr = bufnr or 'BUFFER'
@@ -4981,26 +4982,33 @@ describe('LSP', function()
   end)
 
   describe('cmd', function()
-    it('can connect to lsp server via rpc.connect', function()
+    it('connects to lsp server via rpc.connect using ip address', function()
+      exec_lua(create_tcp_echo_server)
       local result = exec_lua(function()
-        local uv = vim.uv
-        local server = assert(uv.new_tcp())
-        local init = nil
-        server:bind('127.0.0.1', 0)
-        server:listen(127, function(err)
-          assert(not err, err)
-          local socket = assert(uv.new_tcp())
-          server:accept(socket)
-          socket:read_start(require('vim.lsp.rpc').create_read_loop(function(body)
-            init = body
-            socket:close()
-          end))
-        end)
-        local port = server:getsockname().port
+        local server, port, last_message = _G._create_tcp_server('127.0.0.1')
         vim.lsp.start({ name = 'dummy', cmd = vim.lsp.rpc.connect('127.0.0.1', port) })
         vim.wait(1000, function()
-          return init ~= nil
+          return last_message() ~= nil
+        end)
+        local init = last_message()
+        assert(init, 'server must receive `initialize` request')
+        server:close()
+        server:shutdown()
+        return vim.json.decode(init)
+      end)
+      eq('initialize', result.method)
+    end)
+
+    it('connects to lsp server via rpc.connect using hostname', function()
+      skip(is_os('bsd'), 'issue with host resolution in ci')
+      exec_lua(create_tcp_echo_server)
+      local result = exec_lua(function()
+        local server, port, last_message = _G._create_tcp_server('::1')
+        vim.lsp.start({ name = 'dummy', cmd = vim.lsp.rpc.connect('localhost', port) })
+        vim.wait(1000, function()
+          return last_message() ~= nil
         end)
+        local init = last_message()
         assert(init, 'server must receive `initialize` request')
         server:close()
         server:shutdown()