refactor(lsp): define Capability.on_attach

runtime/lua/vim/lsp/_capability.lua

@@ -69,6 +69,16 @@ function M:destroy()
   self.active[self.bufnr] = nil
 end
 
+--- Callback invoked when an LSP client attaches.
+--- Use it to initialize per-client state (empty table, new namespaces, etc.),
+--- or issue requests as needed.
+---@param client_id integer
+function M:on_attach(client_id)
+  self.client_state[client_id] = {}
+end
+
+--- Callback invoked when an LSP client detaches.
+--- Use it to clear per-client state (cached data, extmarks, etc.).
 ---@param client_id integer
 function M:on_detach(client_id)
   self.client_state[client_id] = nil

runtime/lua/vim/lsp/_folding_range.lua

@@ -265,6 +265,11 @@ function State:destroy()
   State.active[self.bufnr] = nil
 end
 
+---@param client_id integer
+function State:on_attach(client_id)
+  self:refresh(vim.lsp.get_client_by_id(client_id))
+end
+
 ---@params client_id integer
 function State:on_detach(client_id)
   self.client_state[client_id] = nil
@@ -273,14 +278,13 @@ function State:on_detach(client_id)
 end
 
 ---@param bufnr integer
----@param client_id? integer
+---@param client_id integer
 function M._setup(bufnr, client_id)
   local state = State.active[bufnr]
   if not state then
     state = State:new(bufnr)
   end
-
-  state:refresh(client_id and vim.lsp.get_client_by_id(client_id))
+  state:on_attach(client_id)
 end
 
 ---@param kind lsp.FoldingRangeKind

runtime/lua/vim/lsp/semantic_tokens.lua

@@ -201,6 +201,9 @@ function STHighlighter:on_attach(client_id)
     }
     self.client_state[client_id] = state
   end
+  if M.is_enabled({ bufnr = self.bufnr }) then
+    self:send_request()
+  end
 end
 
 ---@package
@@ -581,9 +584,6 @@ function M._start(bufnr, client_id, debounce)
   end
 
   highlighter:on_attach(client_id)
-  if M.is_enabled({ bufnr = bufnr }) then
-    highlighter:send_request()
-  end
 end
 
 --- Start the semantic token highlighting engine for the given buffer with the