Re: lib/54510 (libedit: filename completion broken in quote/double quaote)

[Abhinav Upadhyay <er.abhinav.upadhyay%gmail.com@localhost>]

The following reply was made to PR lib/54510; it has been noted by GNATS.

From: Abhinav Upadhyay <er.abhinav.upadhyay%gmail.com@localhost>
To: Tom Lane <tgl%sss.pgh.pa.us@localhost>
Cc: NetBSD GNATS <gnats-bugs%netbsd.org@localhost>, Abhinav Upadhyay <abhinav%netbsd.org@localhost>, 
	Rin Okuyama <rokuyama.rk%gmail.com@localhost>
Subject: Re: lib/54510 (libedit: filename completion broken in quote/double quaote)
Date: Sat, 4 Jan 2020 12:39:29 +0530

 On Sat, Jan 4, 2020 at 6:41 AM Tom Lane <tgl%sss.pgh.pa.us@localhost> wrote:
 >
 > Rin Okuyama <rokuyama.rk%gmail.com@localhost> writes:
 > > (2) In fn_complete(), unescacpe_string() is invoked via
 > > find_word_to_complete(). After that, the cursor position and end of
 > > buffer are substituted to *point and *end, respectively, that are
 > > calculated based on the string before unescaped. Doesn't this break
 > > 3rd party softwares that provide completion_matches and/or
 > > attempted_completion_function?
 >
 > Indeed, I was about to submit a new bug when I noticed this comment.
 > This patch *does* break things for application-specific completion
 > functions, because it strips backslashes from the input word whether
 > that's appropriate or not.  In the Postgres project's "psql"
 > application, one of the things we want to do is tab-complete
 > metacommands that start with backslashes, for instance "\pa<TAB>"
 > should produce "\password".  That works fine with readline, and it
 > worked with libedit up till this patch; but now the completer just
 > sees "pa" so it doesn't know what to do.
 >
 > Given the precedent of other nearby behaviors, maybe the right
 > fix is to skip the unescaping when attempted_completion_function
 > is non-NULL.  I haven't tried to code that though.
 >
 > (We've worked around this, for the moment, by the expedient of
 > ignoring the supplied text altogether in favor of looking into
 > rl_line_buffer [1].  But that's an ugly hack so I'd like to
 > revert it.)
 >
 >                         regards, tom lane
 >
 > [1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=ddd87d564508bb1c80aac0a4439cfe74a3c203a9
 
 Can you verify if this patch fixes the problem?
 
 Index: filecomplete.c
 ===================================================================
 RCS file: /cvsroot/src/lib/libedit/filecomplete.c,v
 retrieving revision 1.62
 diff -u -r1.62 filecomplete.c
 --- filecomplete.c      10 Dec 2019 19:42:09 -0000      1.62
 +++ filecomplete.c      4 Jan 2020 07:07:25 -0000
 @@ -583,10 +583,12 @@
 
  static wchar_t *
  find_word_to_complete(const wchar_t * cursor, const wchar_t * buffer,
 -    const wchar_t * word_break, const wchar_t * special_prefixes,
 size_t * length)
 +    const wchar_t * word_break, const wchar_t * special_prefixes,
 size_t * length,
 +       int do_unescape)
  {
         /* We now look backwards for the start of a filename/variable word */
         const wchar_t *ctemp = cursor;
 +       wchar_t *temp;
         size_t len;
 
         /* if the cursor is placed at a slash or a quote, we need to find the
 @@ -629,10 +631,16 @@
                 ctemp++;
         }
         *length = len;
 -       wchar_t *unescaped_word = unescape_string(ctemp, len);
 -       if (unescaped_word == NULL)
 -               return NULL;
 -       return unescaped_word;
 +       if (!do_unescape) {
 +               wchar_t *unescaped_word = unescape_string(ctemp, len);
 +               if (unescaped_word == NULL)
 +                       return NULL;
 +               return unescaped_word;
 +       }
 +       temp = el_malloc((len + 1) * sizeof(*temp));
 +       (void) wcsncpy(temp, ctemp, len);
 +       temp[len] = '\0';
 +       return temp;
  }
 
  /*
 @@ -662,6 +670,7 @@
         size_t len;
         int what_to_do = '\t';
         int retval = CC_NORM;
 +       int do_unescape = attempted_completion_function == NULL? 1: 0;
 
         if (el->el_state.lastcmd == el->el_state.thiscmd)
                 what_to_do = '?';
 @@ -677,7 +686,7 @@
 
         li = el_wline(el);
         temp = find_word_to_complete(li->cursor,
 -           li->buffer, word_break, special_prefixes, &len);
 +           li->buffer, word_break, special_prefixes, &len, do_unescape);
         if (temp == NULL)
                 goto out;