bug#23566: 25.0.94; sql-sqlite: selecting database file is crippled

[rolf@pointsman.de]

The problem is in 24.5.1 as well as in current 25.1 branch. (Note: you
don't need to use sqlite or have it (and a database file) on your disk,
to see the problem.)


To reproduce:

- Start emacs -Q

- M-x sql-sqlite

This prompts the user to specify a sqlite database file in the
minibuffer. 

Lets assume, you have a sqlite database file in /var/tmp (you don't
actually have to, that's just a path that is assumed to exist at least
on a lot of unix systems).

Try to navigate there in the minibuffer prompt: Remove everthing and
start typing /v, then <Tab> for completion. The prompt doesn't complete
nor provides multiple alternatives, if what you have already typed isn't
unambiguous. You have to spell out (mean: type in) every character of
the path.

(Note: This is only one simple way, to stumble about the problem. It
raises its head also, if you put a buffer in sql-mode, select product
"sqlite" and open a sqli buffer (C-c Tab))

This problem has his roots in the combination of the default value of
the variable sql-sqlite-login-params (which itself is debatable, but
this is not the main point of this bug report) and the implementation of 
sql-get-login-ext, which is called behind the scene, as part of the
implementation of sql-sqlite.

The default value of sql-sqlite-login-params is:
((database :file ".*\\.\\(db\\|sqlite[23]?\\)"))

The crucial part of sql-get-login-ext for this bug report is:

     (cond
      ((plist-member plist :file)
       (expand-file-name
        (read-file-name prompt
                        (file-name-directory last-value) default t
                        (file-name-nondirectory last-value)
                        (when (plist-get plist :file)
                          `(lambda (f)
                             (string-match
                              (concat "\\<" ,(plist-get plist :file) "\\>")
                              (file-name-nondirectory f)))))))
      <more conditions follow>
       
Look at the params of the used read-file-name. Since there is a :file
property in the sql-sqlite-login-params default value, the
read-file-name has a PREDICATE argument, the lambda function

                          `(lambda (f)
                             (string-match
                              (concat "\\<" ,(plist-get plist :file) "\\>")
                              (file-name-nondirectory f)))))))

read-file-name will call this function for every completion candidate
(thats the f argument). The function will return nil for almost all
directory names and most file names (all, that doesn't end in
.db|.sqlite2|.sqlite3), which means they are ruled out as possible
completion candiates. Therefor, tab completion of a sub path doesn't
work, as shown above.

If ever, that cond condition should look like:

      ((plist-member plist :file)
       (expand-file-name
        (read-file-name prompt
                        (file-name-directory last-value) default t
                        (file-name-nondirectory last-value)
                        (when (plist-get plist :file)
                          `(lambda (f)
                             (if (not(file-regular-p))
                                 t
                               (string-match
                                 (concat "\\<" ,(plist-get plist :file) "\\>")
                                 (file-name-nondirectory f))))))))

Note the modification in the lambda function: check for the file name
pattern only, if the completion candidate is a regular file. Everything
else - especially directory names - are valid completion candidates.




In GNU Emacs 25.0.94.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10)
 of 2016-05-17 built on linux-qg7d
Repository revision: a35826dbd44122b97e93d0c67bf658ced0a07ec6
Windowing system distributor 'The X.Org Foundation', version 11.0.11203000
System Description:	openSUSE 12.2 (x86_64)

Configured using:
 'configure --with-modules'

Configured features:
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LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK2 X11 MODULES

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
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Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...
Quit
Making completion list... [2 times]

Load-path shadows:
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Memory information:
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