bug with edit-and-execute-command and multiline commands

[Emanuele Torre]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -march=x86-64 -mtune=generic -O2 -pipe -fno-plt
-DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/bin'
-DSTANDARD_UTILS_PATH='/usr/bin' -DSYS_BASHRC='/etc/bash.bashrc'
-DSYS_BASH_LOGOUT='/etc/bash.bash_logout'
-DNON_INTERACTIVE_LOGIN_SHELLS
uname output: Linux t420 5.10.54-1-lts #1 SMP Wed, 28 Jul 2021
15:05:20 +0000 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.1
Patch Level: 8
Release Status: release

Description:
    rwp suggested me to re report this bug via bashbug instead of using
    savannah since it is the preferred method.

    Here is the original savannah support report:
    https://savannah.gnu.org/support/?110523

    edit-and-execute-command seems to have odd and unintened behaviour
    when used while bash is reading multiline commands that are
    inconsistent between bash versions and patch levels.

    Here are the main ones I noticed in bash 5.1-8.

    If I type-in a multiline command in an interactive bash shell and
    then use edit-and-execute-command, that command will get executed,
    but bash will continue reading for the multiline command.

    Example: if I type-in "if true" newline "then echo hi" newline "else
    echo hello" newline "fi", and then I press \C-x\C-e (to trigger
    edit-and-execute-command) and exit the editor, "hi" will be printed;
    then, if I enter "echo hey" newline "echo good morning" and again
    \C-x\C-e and close the editor, "hi", "hey", and "good morning" get
    printed.

    The behaviour is a bit different (but still probably not intended)
    if the first line is "\" and the second line is a simple commands.

    Example: "\" newline "ls /" \C-x\C-e, when I exit the editor the
    command is executed; then:

     * if I type-in "echo hi" and then press enter, "hi" is printed and
       I get back to the regular bash prompt.
     * if I type-in "echo hi" and then use \C-x\C-e, the editor opens
       with "ls / echo hi" and if I close it, "ls / echo hi" is run, and
       then it keeps reading lines for the command; if I use \C-x\C-e,
       it keeps adding the line as arguments of the command, otherwise,
       if I press return, it executes the last line as a standalone
       command and then it stops reading the multiline command and goes
       back to the regular prompt.

    There is an inaccuracy in the second example of the savannah request
    that I have corrected here: I say that behaviour occurs for simple
    commands, when it actually only occurs if the first line is "\" and
    the second line is a simple command: "ls \" newline "/" behaves
    like the first example.

    NB: The second part of the second example only occurs the simple
    command is an external command: "\" newline "echo hi" \C-x\C-e
    "echo hello" \C-x\C-e opens the editor with "echo hi; echo hello",
    not "echo hi echo hello"

    rwp told me that he experienced different (but still weird)
    behaviours on older bash versions.

    Here is the conversation we had on the #savannah of irc.libera.chat:

    <rwp> Meanwhile...  For bash I think your best process is to send an
          email to the bug-bash AT gnu.org mailing list.
    <emanuele6> oh, ok.
    <rwp> That's where Chet mostly handles bash bugs.
    <emanuele6> thank you for the help, rwp!
    <rwp> I'm just reading your bug reproducer very carefully now...
    <rwp> That does seem pretty weird behavior around C-x C-e which I
          can't think of a time I have ever done on the command line
          myself before.
    <rwp> I actually get different behavior than what you report. But it
          is still not expected either. So something bizarre going on
          there.
    <rwp> What I see is that it doesn't actually execute the command.
          And if I am left looking at the PS4 "> " prompt.
    <rwp> All attempts to terminate the command at that point result in
          a "bash: syntax error near unexpected token `;'" message.
    <emanuele6> oh
    <emanuele6> i also tried my examples with `bash --norc` and they had
                the same behaviour
    <emanuele6> i mean the same behaviours that i described on the sr
    <emanuele6> so maybe it is your configuration
    <rwp> I am running bash-5.1-3 here. You are running 5.1-8. But it is
          different yet again in bash-4.4-5 too.
    <emanuele6> i see
    <rwp> In 4.4 I get an immediate syntax
          "bash: syntax error near unexpected token `fi'"
    <rwp> Good bug!

Repeat-By:
    example 1:
        $ EDITOR=vi       |
        $ \               |
    > echo hello      | enter ^X^E; vi will open with "echo hello"; exit with :q
    hello             |
    > echo hi         | the prompt keeps showing PS4 instead of PS1; hit return
    hi                |
    $                 |

    example 2 (this only occurs with external commands like ls(1), not
with echo):
        $ EDITOR=vi        |
        $ \                |
    > ls /             | enter ^X^E; vi will open with "ls /"; exit
    [contents of /]    |
    > /tmp             | enter ^X^E; vi will open with "ls / /tmp"; exit
    [contents of /]    |
    [contents of /tmp] |
    > echo hey         | hit return
    hey                |
    $                  |

    example 3:
        $ EDITOR=vi       |
    $ if true         |
    > then echo hi    |
    > else echo hello |
    > fi              | enter ^X^E; vi will open with
                         "if true; then echo hi; else echo hello; fi"; exit
    hi                |
    > echo hey        |
    > echo morning    | enter ^X^E; vi will open with what it had before
                         plus "; echo hey; echo morning"; exit
    hi                |
    hey               |
    morning           |
    > echo not run    |
    > ^C              | enter ^C
    $                 |

    I had also recorded a GIF showing me repeating examples similar to
    "example 1" and "example 3" that might help understand the bug
    better.
    Here is a link to download it from savannah:
    https://savannah.gnu.org/support/download.php?file_id=51741

    Also here is a paste with some examples by rwp:
    https://paste.debian.net/plain/1206849