fix(lsp): autotrigger should only trigger on client's triggerCharacters (#32266)

Problem: autotrigger option of vim.lsp.completion.enable() would trigger
all clients, as long as it matched at least one client's
triggerCharacters.

Solution: trigger only the clients with triggerCharacters matching the
character. overtriggering still happens if any client returns
isIncomplete=true (this case is more involved).


Co-authored-by: Mathias Fussenegger <f.mathias@zignar.net>

runtime/lua/vim/lsp/completion.lua

@@ -518,11 +518,14 @@ local function on_insert_char_pre(handle)
   end
 
   local char = api.nvim_get_vvar('char')
-  if not completion_timer and handle.triggers[char] then
+  local matched_clients = handle.triggers[char]
+  if not completion_timer and matched_clients then
     completion_timer = assert(vim.uv.new_timer())
     completion_timer:start(25, 0, function()
       reset_timer()
-      vim.schedule(M.trigger)
+      vim.schedule(function()
+        trigger(api.nvim_get_current_buf(), matched_clients)
+      end)
     end)
   end
 end

test/functional/plugin/lsp/completion_spec.lua

@@ -770,13 +770,14 @@ end)
 
 --- @param name string
 --- @param completion_result lsp.CompletionList
+--- @param trigger_chars? string[]
 --- @return integer
-local function create_server(name, completion_result)
+local function create_server(name, completion_result, trigger_chars)
   return exec_lua(function()
     local server = _G._create_server({
       capabilities = {
         completionProvider = {
-          triggerCharacters = { '.' },
+          triggerCharacters = trigger_chars or { '.' },
         },
       },
       handlers = {
@@ -793,6 +794,7 @@ local function create_server(name, completion_result)
       cmd = server.cmd,
       on_attach = function(client, bufnr0)
         vim.lsp.completion.enable(true, client.id, bufnr0, {
+          autotrigger = trigger_chars ~= nil,
           convert = function(item)
             return { abbr = item.label:gsub('%b()', '') }
           end,
@@ -957,6 +959,39 @@ describe('vim.lsp.completion: protocol', function()
     end)
   end)
 
+  it('insert char triggers clients matching trigger characters', function()
+    local results1 = {
+      isIncomplete = false,
+      items = {
+        {
+          label = 'hello',
+        },
+      },
+    }
+    create_server('dummy1', results1, { 'e' })
+    local results2 = {
+      isIncomplete = false,
+      items = {
+        {
+          label = 'hallo',
+        },
+      },
+    }
+    create_server('dummy2', results2, { 'h' })
+
+    feed('h')
+    exec_lua(function()
+      vim.v.char = 'h'
+      vim.cmd.startinsert()
+      vim.api.nvim_exec_autocmds('InsertCharPre', {})
+    end)
+
+    assert_matches(function(matches)
+      eq(1, #matches)
+      eq('hallo', matches[1].word)
+    end)
+  end)
+
   it('executes commands', function()
     local completion_list = {
       isIncomplete = false,