feat(lsp): implement workspace/didChangeWatchedFiles (#22405)

runtime/lua/vim/lsp/handlers.lua

@@ -117,15 +117,35 @@ M['window/showMessageRequest'] = function(_, result)
 end
 
 --see: https://microsoft.github.io/language-server-protocol/specifications/specification-current/#client_registerCapability
-M['client/registerCapability'] = function(_, _, ctx)
-  local client_id = ctx.client_id
-  local warning_tpl = 'The language server %s triggers a registerCapability '
-    .. 'handler despite dynamicRegistration set to false. '
-    .. 'Report upstream, this warning is harmless'
-  local client = vim.lsp.get_client_by_id(client_id)
-  local client_name = client and client.name or string.format('id=%d', client_id)
-  local warning = string.format(warning_tpl, client_name)
-  log.warn(warning)
+M['client/registerCapability'] = function(_, result, ctx)
+  local log_unsupported = false
+  for _, reg in ipairs(result.registrations) do
+    if reg.method == 'workspace/didChangeWatchedFiles' then
+      require('vim.lsp._watchfiles').register(reg, ctx)
+    else
+      log_unsupported = true
+    end
+  end
+  if log_unsupported then
+    local client_id = ctx.client_id
+    local warning_tpl = 'The language server %s triggers a registerCapability '
+      .. 'handler despite dynamicRegistration set to false. '
+      .. 'Report upstream, this warning is harmless'
+    local client = vim.lsp.get_client_by_id(client_id)
+    local client_name = client and client.name or string.format('id=%d', client_id)
+    local warning = string.format(warning_tpl, client_name)
+    log.warn(warning)
+  end
+  return vim.NIL
+end
+
+--see: https://microsoft.github.io/language-server-protocol/specifications/specification-current/#client_unregisterCapability
+M['client/unregisterCapability'] = function(_, result, ctx)
+  for _, unreg in ipairs(result.unregisterations) do
+    if unreg.method == 'workspace/didChangeWatchedFiles' then
+      require('vim.lsp._watchfiles').unregister(unreg, ctx)
+    end
+  end
   return vim.NIL
 end