feat(lsp): add function to clear codelens (#21504)

Currently once you retrieve the lenses you're pretty much stuck with
them as saving new lenses is additive.

Adding a dedicated method to reset lenses allows users to toggle lenses
on/off which can be useful for language servers where they are noisy or
expensive and you only want to see them temporary.

runtime/lua/vim/lsp/codelens.lua

@@ -108,13 +108,36 @@ function M.run()
   end
 end
 
+---@private
+local function resolve_bufnr(bufnr)
+  return bufnr == 0 and api.nvim_get_current_buf() or bufnr
+end
+
+--- Clear the lenses
+---
+---@param client_id number|nil filter by client_id. All clients if nil
+---@param bufnr number|nil filter by buffer. All buffers if nil
+function M.clear(client_id, bufnr)
+  local buffers = bufnr and { resolve_bufnr(bufnr) } or vim.tbl_keys(lens_cache_by_buf)
+  for _, iter_bufnr in pairs(buffers) do
+    local client_ids = client_id and { client_id } or vim.tbl_keys(namespaces)
+    for _, iter_client_id in pairs(client_ids) do
+      local ns = namespaces[iter_client_id]
+      lens_cache_by_buf[iter_bufnr][iter_client_id] = {}
+      api.nvim_buf_clear_namespace(iter_bufnr, ns, 0, -1)
+    end
+  end
+end
+
 --- Display the lenses using virtual text
 ---
 ---@param lenses table of lenses to display (`CodeLens[] | null`)
 ---@param bufnr number
 ---@param client_id number
 function M.display(lenses, bufnr, client_id)
+  local ns = namespaces[client_id]
   if not lenses or not next(lenses) then
+    api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
     return
   end
   local lenses_by_lnum = {}
@@ -126,7 +149,6 @@ function M.display(lenses, bufnr, client_id)
     end
     table.insert(line_lenses, lens)
   end
-  local ns = namespaces[client_id]
   local num_lines = api.nvim_buf_line_count(bufnr)
   for i = 0, num_lines do
     local line_lenses = lenses_by_lnum[i] or {}