fix(runtime): don't use regexes inside lua require'mod'

Fixes #15147 and fixes #15497. Also sketch "subdir" caching. Currently
this only caches whether an rtp entry has a "lua/" subdir but we could
consider cache other subdirs potentially or even "lua/mybigplugin/"
possibly.

Note: the async_leftpad test doesn't actually fail on master, at least
not deterministically (even when disabling the fast_breakcheck
throttling). It's still useful as a regression test for further changes
and included as such.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index 3f93bb9a09..59ebafd9c8 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -790,7 +790,7 @@ int nlua_call(lua_State *lstate)
   Error err = ERROR_INIT;
   size_t name_len;
   const char_u *name = (const char_u *)luaL_checklstring(lstate, 1, &name_len);
-  if (!nlua_is_deferred_safe(lstate)) {
+  if (!nlua_is_deferred_safe()) {
     return luaL_error(lstate, e_luv_api_disabled, "vimL function");
   }
 
@@ -846,7 +846,7 @@ free_vim_args:
 
 static int nlua_rpcrequest(lua_State *lstate)
 {
-  if (!nlua_is_deferred_safe(lstate)) {
+  if (!nlua_is_deferred_safe()) {
     return luaL_error(lstate, e_luv_api_disabled, "rpcrequest");
   }
   return nlua_rpc(lstate, true);
@@ -1316,7 +1316,7 @@ Object nlua_call_ref(LuaRef ref, const char *name, Array args, bool retval, Erro
 
 /// check if the current execution context is safe for calling deferred API
 /// methods. Luv callbacks are unsafe as they are called inside the uv loop.
-bool nlua_is_deferred_safe(lua_State *lstate)
+bool nlua_is_deferred_safe(void)
 {
   return in_fast_callback == 0;
 }