add support to show diagnostics count in statusline (#11641)

* add support to show diagnostics count in statusline
* documentation

runtime/lua/vim/lsp.lua

@@ -893,21 +893,22 @@ function lsp.buf_request_sync(bufnr, method, params, timeout_ms)
   return request_results
 end
 
---- Sends a notification to all servers attached to the buffer.
----
---@param bufnr (optional, number) Buffer handle, or 0 for current
---@param method (string) LSP method name
---@param params (string) Parameters to send to the server
----
---@returns nil
+--- Send a notification to a server
+-- @param bufnr [number] (optional): The number of the buffer
+-- @param method [string]: Name of the request method
+-- @param params [string]: Arguments to send to the server
+--
+-- @returns true if any client returns true; false otherwise
 function lsp.buf_notify(bufnr, method, params)
   validate {
     bufnr    = { bufnr, 'n', true };
     method   = { method, 's' };
   }
+  local resp = false
   for_each_buffer_client(bufnr, function(client, _client_id)
-    client.rpc.notify(method, params)
+    if client.rpc.notify(method, params) then resp = true end
   end)
+  return resp
 end
 
 --- Implements 'omnifunc' compatible LSP completion.

runtime/lua/vim/lsp/buf.lua

@@ -23,6 +23,10 @@ local function request(method, params, callback)
   return vim.lsp.buf_request(0, method, params, callback)
 end
 
+function M.server_ready()
+  return not not vim.lsp.buf_notify(0, "window/progress", {})
+end
+
 function M.hover()
   local params = util.make_position_params()
   request('textDocument/hover', params)

runtime/lua/vim/lsp/callbacks.lua

@@ -33,6 +33,7 @@ M['textDocument/publishDiagnostics'] = function(_, _, result)
   util.buf_diagnostics_underline(bufnr, result.diagnostics)
   util.buf_diagnostics_virtual_text(bufnr, result.diagnostics)
   -- util.set_loclist(result.diagnostics)
+  vim.api.nvim_command("doautocmd User LspDiagnosticsChanged")
 end
 
 M['textDocument/references'] = function(_, _, result)

runtime/lua/vim/lsp/util.lua

@@ -743,6 +743,18 @@ do
       api.nvim_buf_set_virtual_text(bufnr, diagnostic_ns, line, virt_texts, {})
     end
   end
+  function M.buf_diagnostics_count(kind)
+    local bufnr = vim.api.nvim_get_current_buf()
+    local buffer_line_diagnostics = all_buffer_diagnostics[bufnr]
+    if not buffer_line_diagnostics then return end
+    local count = 0
+    for _, line_diags in pairs(buffer_line_diagnostics) do
+      for _, diag in ipairs(line_diags) do
+        if protocol.DiagnosticSeverity[kind] == diag.severity then count = count + 1 end
+      end
+    end
+    return count
+  end
 end
 
 local position_sort = sort_by_key(function(v)