fix(rpc): break nvim_error_event feedback loop between two nvim instances

In case nvim A sends nvim_error_event to nvim B, it would
respond with another nvim_error_event due to unknown
request name. Fix this by adding dummy request handler for now.

scripts/gen_vimdoc.py

@@ -947,7 +947,8 @@ def fmt_doxygen_xml_as_vimhelp(filename, target):
 
         func_doc = "\n".join(split_lines)
 
-        if name.startswith(CONFIG[target]['fn_name_prefix']):
+        if (name.startswith(CONFIG[target]['fn_name_prefix'])
+           and name != "nvim_error_event"):
             fns_txt[name] = func_doc
 
     return ('\n\n'.join(list(fns_txt.values())),

src/nvim/api/vim.c

@@ -2256,3 +2256,11 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
   return result;
 }
+
+void nvim_error_event(uint64_t channel_id, Integer lvl, String data)
+  FUNC_API_REMOTE_ONLY
+{
+  // TODO(bfredl): consider printing message to user, as will be relevant
+  // if we fork nvim processes as async workers
+  ELOG("async error on channel %" PRId64 ": %s", channel_id, data.size ? data.data : "");
+}

src/nvim/generators/gen_api_dispatch.lua

@@ -91,7 +91,7 @@ local deprecated_aliases = require("api.dispatch_deprecated")
 for _,f in ipairs(shallowcopy(functions)) do
   local ismethod = false
   if startswith(f.name, "nvim_") then
-    if startswith(f.name, "nvim__") then
+    if startswith(f.name, "nvim__") or f.name == "nvim_error_event" then
       f.since = -1
     elseif f.since == nil then
       print("Function "..f.name.." lacks since field.\n")
@@ -149,7 +149,7 @@ local exported_attributes = {'name', 'return_type', 'method',
                              'since', 'deprecated_since'}
 local exported_functions = {}
 for _,f in ipairs(functions) do
-  if not startswith(f.name, "nvim__") then
+  if not (startswith(f.name, "nvim__") or f.name == "nvim_error_event") then
     local f_exported = {}
     for _,attr in ipairs(exported_attributes) do
       f_exported[attr] = f[attr]