bug#36828: 27.0.50; Uninstalled emacs shows installed documentation

[Óscar Fuentes]

Sorry for the long delay.

Eli Zaretskii <eliz@gnu.org> writes:

>> >> M-x describe-function shows the docstrings of the Emacs I'm executing,
>> >
>> > How do you know?  What is the value of doc-directory?
>> 
>> /home/oscar/dev/emacs/stable/build/etc/
>> 
>> The installed version is in /usr/local.
>
> Hmm... then this is not the use case I had in mind, and some other
> factor is at work here.  Your use case is supposed to be handled by
> this fragment from init_callproc:

What follows is the result of a debug session for the chunk of code you
indicated.

  if (data_dir == 0)
    {
      Lisp_Object tem, srcdir;
      Lisp_Object lispdir = Fcar (decode_env_path (0, PATH_DUMPLOADSEARCH, 0));

      srcdir = Fexpand_file_name (build_string ("../src/"), lispdir);

      tem = Fexpand_file_name (build_string ("NEWS"), Vdata_directory);

Vdata_directory is "/usr/local/share/emacs/27.0.50/etc/"

tem is "/usr/local/share/emacs/27.0.50/etc/NEWS"

srcdir is "/home/oscar/dev/emacs/emacs/src/"

Vinvocation_directory is "/home/oscar/dev/emacs/debug/src/"

      if (!NILP (Fequal (srcdir, Vinvocation_directory))
          || NILP (Ffile_exists_p (tem)))
        {

Execution never enters this block, because srcdir !=
Vinvocation_directory (because this is an out-of-source build) and
"/usr/local/share/emacs/27.0.50/etc/NEWS" exists (because emacs was
installed on the past).

          Lisp_Object newdir;
          newdir = Fexpand_file_name (build_string ("../etc/"), lispdir);
          tem = Fexpand_file_name (build_string ("NEWS"), newdir);
          if (!NILP (Ffile_exists_p (tem)))
            Vdata_directory = newdir;
        }
    }

The code basically ignores the local, non-installed NEWS when there is
an installed NEWS and we are executing from an out-of-source build tree.

I propose the reverse: unconditionally test for the non-installed NEWS and
adjust Vdata_directory if it exists. Something like this (untested for
the installed emacs case):

modified   src/callproc.c
@@ -1560,21 +1560,13 @@ init_callproc (void)
      source directory.  */
   if (data_dir == 0)
     {
-      Lisp_Object tem, srcdir;
+      Lisp_Object tem, etcdir;
       Lisp_Object lispdir = Fcar (decode_env_path (0, PATH_DUMPLOADSEARCH, 0));
 
-      srcdir = Fexpand_file_name (build_string ("../src/"), lispdir);
-
-      tem = Fexpand_file_name (build_string ("NEWS"), Vdata_directory);
-      if (!NILP (Fequal (srcdir, Vinvocation_directory))
-         || NILP (Ffile_exists_p (tem)))
-       {
-         Lisp_Object newdir;
-         newdir = Fexpand_file_name (build_string ("../etc/"), lispdir);
-         tem = Fexpand_file_name (build_string ("NEWS"), newdir);
-         if (!NILP (Ffile_exists_p (tem)))
-           Vdata_directory = newdir;
-       }
+      etcdir = Fexpand_file_name (build_string ("../etc/"), lispdir);
+      tem = Fexpand_file_name (build_string ("NEWS"), etcdir);
+      if (!NILP (Ffile_exists_p (tem)))
+        Vdata_directory = newdir;
     }
 
   if (!will_dump_p ())