fix(events): don't expand non-file as file name

src/nvim/autocmd.c

@@ -1676,6 +1676,7 @@ bool apply_autocmds_group(event_T event, char *fname, char *fname_io, bool force
         || event == EVENT_USER || event == EVENT_WINCLOSED
         || event == EVENT_WINRESIZED || event == EVENT_WINSCROLLED) {
       fname = xstrdup(fname);
+      autocmd_fname_full = true;  // don't expand it later
     } else {
       fname = FullName_save(fname, false);
     }

src/nvim/path.c

@@ -2087,17 +2087,17 @@ char *path_shorten_fname(char *full_path, char *dir_name)
   assert(dir_name != NULL);
   size_t len = strlen(dir_name);
 
-  // If dir_name is a path head, full_path can always be made relative.
-  if (len == (size_t)path_head_length() && is_path_head(dir_name)) {
-    return full_path + len;
-  }
-
   // If full_path and dir_name do not match, it's impossible to make one
   // relative to the other.
   if (path_fnamencmp(dir_name, full_path, len) != 0) {
     return NULL;
   }
 
+  // If dir_name is a path head, full_path can always be made relative.
+  if (len == (size_t)path_head_length() && is_path_head(dir_name)) {
+    return full_path + len;
+  }
+
   char *p = full_path + len;
 
   // If *p is not pointing to a path separator, this means that full_path's

test/functional/api/autocmd_spec.lua

@@ -228,23 +228,28 @@ describe('autocmd api', function()
     end)
 
     it('receives an args table', function()
-      local res = exec_lua [[
-        local group_id = vim.api.nvim_create_augroup("TestGroup", {})
-        local autocmd_id = vim.api.nvim_create_autocmd("User", {
+      local group_id = meths.create_augroup("TestGroup", {})
+      -- Having an existing autocmd calling expand("<afile>") shouldn't change args #18964
+      meths.create_autocmd('User', {
+        group = 'TestGroup',
+        pattern = 'Te*',
+        command = 'call expand("<afile>")',
+      })
+
+      local autocmd_id = exec_lua [[
+        return vim.api.nvim_create_autocmd("User", {
           group = "TestGroup",
           pattern = "Te*",
           callback = function(args)
             vim.g.autocmd_args = args
           end,
         })
-
-        return {group_id, autocmd_id}
       ]]
 
       meths.exec_autocmds("User", {pattern = "Test pattern"})
       eq({
-        id = res[2],
-        group = res[1],
+        id = autocmd_id,
+        group = group_id,
         event = "User",
         match = "Test pattern",
         file = "Test pattern",
@@ -252,27 +257,24 @@ describe('autocmd api', function()
       }, meths.get_var("autocmd_args"))
 
       -- Test without a group
-      res = exec_lua [[
-        local autocmd_id = vim.api.nvim_create_autocmd("User", {
+      autocmd_id = exec_lua [[
+        return vim.api.nvim_create_autocmd("User", {
           pattern = "*",
           callback = function(args)
             vim.g.autocmd_args = args
           end,
         })
-
-        return {autocmd_id}
       ]]
 
       meths.exec_autocmds("User", {pattern = "some_pat"})
       eq({
-        id = res[1],
+        id = autocmd_id,
         group = nil,
         event = "User",
         match = "some_pat",
         file = "some_pat",
         buf = 1,
       }, meths.get_var("autocmd_args"))
-
     end)
 
     it('can receive arbitrary data', function()