feat(lsp): show server name in code actions #30830

Problem:
If there are multiple LSP clients, it's not clear which actions are provided by which servers. #30710

Solution:
Show the server name next to each action (only if there are multiple clients).

runtime/doc/news.txt

@@ -182,6 +182,8 @@ LSP
 • |vim.lsp.buf.format()| now supports passing a list of ranges
   via the `range` parameter (this requires support for the
   `textDocument/rangesFormatting` request).
+• |vim.lsp.buf.code_action()| actions show client name when there are multiple
+  clients.
 
 LUA
 

runtime/lua/vim/lsp/buf.lua

@@ -827,11 +827,19 @@ local function on_code_action_results(results, opts)
     return
   end
 
-  ---@param item {action: lsp.Command|lsp.CodeAction}
+  ---@param item {action: lsp.Command|lsp.CodeAction, ctx: lsp.HandlerContext}
   local function format_item(item)
-    local title = item.action.title:gsub('\r\n', '\\r\\n')
+    local clients = vim.lsp.get_clients({ bufnr = item.ctx.bufnr })
-    return title:gsub('\n', '\\n')
+    local title = item.action.title:gsub('\r\n', '\\r\\n'):gsub('\n', '\\n')
+
+    if #clients == 1 then
+      return title
     end
+
+    local source = vim.lsp.get_client_by_id(item.ctx.client_id).name
+    return ('%s [%s]'):format(title, source)
+  end
+
   local select_opts = {
     prompt = 'Code actions:',
     kind = 'codeaction',