Subject: bug#22169: 25.0.50; File name compiletion doesn't work with non-ASCII characters on OS X

From: Anders Lindgren <[email-masked]>
Date: Mon, 21 Dec 2015 23:03:38 +0100

Hi!

I just tested your latest patch. Unfortunately, it doesn't work properly.

When pressing TAB, it expands the characters correctly. However,
`file-name-all-completions' doesn't work:

(file-name-all-completions "a" ".")
("åäöfirst.txt" "aaosecond.txt")

I haven't had time to see what actually happens in the code, though.
However, the "  if (STRING_MULTIBYTE (file))" looks suspicious as the
decoded value needs to be checked even for strings like "a". (However, I
don't really know what STRING_MULTIBYTE does.)

    -- Anders

On Mon, Dec 21, 2015 at 5:09 PM, Eli Zaretskii <[email-masked]> wrote:

> > Date: Mon, 21 Dec 2015 07:52:53 +0100
> > From: Anders Lindgren <[email-masked]>
> > Cc: [email-masked], [email-masked]
> >
> > I did some simple measurements with and without this patch. I ran
> > `(file-name-all-completions "x" "src")' on the Emacs src directory. The
> timing
> > values were almost identical (varying between 0.001012 and 0.001080).
>
> You should try it on a larger directory, preferably one that has many
> files with non-ASCII file names.
>
> > The way I see it, the patch doesn't do any harm in any coding system,
> and it is
> > fast. Hence, I don't really see that it's worth the effort to make this
> code
> > conditional.
>
> I'm surprised to hear that.  Did you look at the implementation of
> Fcompare_strings?  It's highly non-trivial.  What's more, if the user
> sets completion-ignore-case non-nil, Fcompare_strings will call
> Fupcase on each character, which is another non-trivial function; if
> you are particularly unlucky, Fupcase can even GC (if it needs to set
> up the case-table), which will definitely take several hundreds of
> milliseconds if not longer.
>
> And that's today; what if tomorrow someone comes and adds to
> Fcompare_strings something that makes it even more complex and slow?
>
> I've learned long ago not to call any non-trivial API unless I really
> need it.  You can never know what complexity hides in there.  Besides,
> it simply looks bad in the code to do processing that is unnecessary.
>
> > However, please write a patch for this if you still thinks it's
> necessary. I
> > can test it here to make sure it works under OS X.
>
> Attached (relative to the current emacs-25 branch).
>
> Please note that the patch below attempts to solve a couple of
> additional subtle aspects of this:
>
>   . it doesn't force the extra comparison for unibyte strings (which
>     include ASCII strings and unibyte non-ASCII strings), since the
>     issue doesn't exist then, and ENCODE_FILE/DECODE_FILE are no-ops
>
>   . it forces the FILE argument to have all of its characters
>     precomposed, since if the caller passes us a file name with
>     decomposed characters, we risk rejecting them in the code we are
>     adding
>
> Please see that these indeed o their job correctly, as I could only
> test the code very superficially.
>
> Thanks.
>
> diff --git a/lisp/international/ucs-normalize.el
> b/lisp/international/ucs-normalize.el
> index 8839b00..6f2fb28 100644
> --- a/lisp/international/ucs-normalize.el
> +++ b/lisp/international/ucs-normalize.el
> @@ -627,6 +627,10 @@ 'utf-8-hfs
>    :pre-write-conversion 'ucs-normalize-hfs-nfd-pre-write-conversion
>    )
>
> +;; This is tested in dired.c:file_name_completion in order to reject
> +;; false positives due to comparison of encoded file names.
> +(coding-system-put 'utf-8-hfs 'decomposed-characters 't)
> +
>  (provide 'ucs-normalize)
>
>  ;; Local Variables:
> diff --git a/src/dired.c b/src/dired.c
> index 84bf247..d5628d5 100644
> --- a/src/dired.c
> +++ b/src/dired.c
> @@ -467,6 +467,7 @@ file_name_completion (Lisp_Object file, Lisp_Object
> dirname, bool all_flag,
>       well as "." and "..".  Until shown otherwise, assume we can't exclude
>       anything.  */
>    bool includeall = 1;
> +  bool check_decoded = false;
>    ptrdiff_t count = SPECPDL_INDEX ();
>
>    elt = Qnil;
> @@ -485,6 +486,28 @@ file_name_completion (Lisp_Object file, Lisp_Object
> dirname, bool all_flag,
>       on the encoded file name.  */
>    encoded_file = ENCODE_FILE (file);
>    encoded_dir = ENCODE_FILE (Fdirectory_file_name (dirname));
> +  if (STRING_MULTIBYTE (file))
> +    {
> +      Lisp_Object file_encoding = Vfile_name_coding_system;
> +
> +      if (NILP (Vfile_name_coding_system))
> +       file_encoding = Vdefault_file_name_coding_system;
> +      /* If the file-name encoding decomposes characters, as we do for
> +        HFS+ filesystems, we need to make an additional comparison of
> +        decoded names in order to filter false positives, such as "a"
> +        falsely matching "a-ring".  */
> +      if (!NILP (file_encoding)
> +         && !NILP (Fplist_get (Fcoding_system_plist (file_encoding),
> +                               Qdecomposed_characters)))
> +       {
> +         check_decoded = true;
> +         /* Recompute FILE to make sure any decomposed characters in
> +            it are re-composed by the post-read-conversion.
> +            Otherwise, any decomposed characters will be rejected by
> +            the additional check below.  */
> +         file = DECODE_FILE (encoded_file);
> +       }
> +    }
>    int fd;
>    DIR *d = open_directory (encoded_dir, &fd);
>    record_unwind_protect_ptr (directory_files_internal_unwind, d);
> @@ -637,6 +660,21 @@ file_name_completion (Lisp_Object file, Lisp_Object
> dirname, bool all_flag,
>        if (!NILP (predicate) && NILP (call1 (predicate, name)))
>         continue;
>
> +      /* Reject entries where the encoded strings match, but the
> +         decoded don't.  For example, "a" should not match "a-ring" on
> +         file systems that store decomposed characters. */
> +      Lisp_Object zero = make_number (0);
> +      Lisp_Object compare;
> +      Lisp_Object cmp;
> +      if (check_decoded && SCHARS (file) <= SCHARS (name))
> +       {
> +         compare = make_number (SCHARS (file));
> +         cmp = Fcompare_strings (name, zero, compare, file, zero, compare,
> +                                 completion_ignore_case ? Qt : Qnil);
> +         if (!EQ (cmp, Qt))
> +           continue;
> +       }
> +
>        /* Suitably record this match.  */
>
>        matchcount += matchcount <= 1;
> @@ -650,15 +688,13 @@ file_name_completion (Lisp_Object file, Lisp_Object
> dirname, bool all_flag,
>         }
>        else
>         {
> -         Lisp_Object zero = make_number (0);
>           /* FIXME: This is a copy of the code in Ftry_completion.  */
> -         ptrdiff_t compare = min (bestmatchsize, SCHARS (name));
> -         Lisp_Object cmp
> -           = Fcompare_strings (bestmatch, zero,
> -                               make_number (compare),
> -                               name, zero,
> -                               make_number (compare),
> -                               completion_ignore_case ? Qt : Qnil);
> +         compare = min (bestmatchsize, SCHARS (name));
> +         cmp = Fcompare_strings (bestmatch, zero,
> +                                 make_number (compare),
> +                                 name, zero,
> +                                 make_number (compare),
> +                                 completion_ignore_case ? Qt : Qnil);
>           ptrdiff_t matchsize = EQ (cmp, Qt) ? compare : eabs (XINT (cmp))
> - 1;
>
>           if (completion_ignore_case)
> @@ -1007,6 +1043,7 @@ syms_of_dired (void)
>    DEFSYM (Qfile_attributes, "file-attributes");
>    DEFSYM (Qfile_attributes_lessp, "file-attributes-lessp");
>    DEFSYM (Qdefault_directory, "default-directory");
> +  DEFSYM (Qdecomposed_characters, "decomposed-characters");
>
>    defsubr (&Sdirectory_files);
>    defsubr (&Sdirectory_files_and_attributes);
>