[PATCH] Switch vi-insert TAB binding only for the default binding

[Koichi Murase]

Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -O2 -march=native -Wno-parentheses -Wno-format-security
uname output: Linux padparadscha 4.13.13-100.fc25.i686 #1 SMP Wed Nov
15 18:24:19 UTC 2017 i686 i686 i386 GNU/Linux
Machine Type: i686-pc-linux-gnu

Bash Version: 5.0
Patch Level: 0
Release Status: release

Description:

  In vi editing mode, I bind TAB to a shell command using `bind -x'.
However, when I use the POSIX mode locally in functions something like

    f() {
      local POSIXLY_CORRECT=y
      # do something
    }

  the binding is reset every time the function is called. It is
annoying to rebind TAB after every calls of such functions. This
behavior is caused by `int posix_readline_initialize (on_or_off)'
defined in `bashline.c'. The reason of the current behavior is
explained in

    http://lists.gnu.org/archive/html/bug-bash/2014-06/msg00049.html

Repeat-By:

  Defaultly TAB is bound to the rl function `complete'.

    $ set -o vi
    $ bind -q complete
    complete can be invoked via "\C-i".

  With `bind -x' one can bind TAB to another operation. When one type
TAB, the user-defined binding works.

    $ bind -x '"\t": echo hello'
    $ bind -q complete
    complete is not bound to any keys.
    hello # <-- `echo hello' is executed by TAB
    $

  However, after using local POSIX mode, the binding does not work.

    $ f() { local POSIXLY_CORRECT=y; }; f
    $ # <-- nothing happens with TAB

  The binding is turned back to the default.

    $ bind -q complete
    complete can be invoked via "\C-i".

Fix:

  There may be several choices to fix this.

  a. One is to introduce a new variable that memorizes whether the
binding has been defined by users or not. Or, maybe there are other
ways to manage the information. Then, only when the binding is not
defined by users, switch the binding. However the code to update the
variable would become dirty (i.e., maybe one needs to add codes to
readline).

  b. Another way is to switch the binding only when the current
binding is the same with the default one. The implementation is
simple, but not complete: when the user-defined binding is the same
with the default one, the binding will be switched unexpectedly.
Nevertheless this is far better than the current behavior.

  I made a patch for the choice `b'. I attach the patch.

Best regards,
Koichi

0001-keep-user-key-bindings-of-TAB-on-switching-POSIX-mod.patch
Description: Binary data