Silent mode ex (-s) has different exit code than non-silent based on presence of line continuation in vimscript plugin

[lucianposton]

Describe the bug
ex -s exits with failure code (1) while ex exits success code (0) when a plugin's vimscript contains a line continuation with backslash.

Examples of vimscript causing this issue:

command! -bang -nargs=+ -range=0 -complete=file AsyncRun 
	\ call asyncrun#run('<bang>', '', <q-args>, <count>, <line1>, <line2>)

echo "a
            \ b"

Example of vimscript not causing this issue:

echo "a b"

To Reproduce
Step 1:
Empty ~/.vimrc and ~/.vim.
Step 2:

echo "foo" > /tmp/test.file

Step 3:

ex -sc '%s/foo/bar/|x' /tmp/test.file

Step 4:

$ echo $?
0

Step 5:

echo "foo" > /tmp/test.file

Step 6:

ex -c '%s/foo/bar/|x' /tmp/test.file

Step 7:

$ echo $?
0

Step 8:

mkdir -p ~/.vim/plugin && echo "echo \"a\n            \\\\ b\"" > ~/.vim/plugin/bug.vim

Step 9:

echo "foo" > /tmp/test.file

Step 10:

ex -sc '%s/foo/bar/|x' /tmp/test.file

Step 11:

$ echo $?
1

Step 12:

echo "foo" > /tmp/test.file

Step 13:

ex -c '%s/foo/bar/|x' /tmp/test.file

Step 14:

$ echo $?
0

Step 15:

echo "echo \"a b\"" > ~/.vim/plugin/bug.vim

Step 16:

echo "foo" > /tmp/test.file

Step 17:

ex -sc '%s/foo/bar/|x' /tmp/test.file

Step 18:

$ echo $?
0

Step 19:

echo "foo" > /tmp/test.file

Step 20:

ex -c '%s/foo/bar/|x' /tmp/test.file

Step 21:

$ echo $?
0

Expected behavior
Expected behavior is that step 11 has the same exit code as steps 4, 7, 14, 18, and 21.

Environment (please complete the following information):

• Vim version: 8.2.0055, also tested with 8.2.0246 compiled from source
• OS: gentoo linux
• Terminal: rxvt-unicode

Additional context

[tonymec]

What is 'compatible' set to? :verbose set cp? (as a line in your script in your -s runs, or typed from the keyboard otherwise) will tell you. Since this is a Boolean option, the question mark at the end is important.

compatible needs to be off for continuation lines (lines starting with a backslash in sourced scripts) to be recognised as such.

• If Vim finds a vimrc (even an empty one), that wil set 'nocompatible'
• If a recent version of Vim finds neither a vimrc nor an exrc, it will source $VIMRUNTIME/defaults.vim, which will set 'nocompatible'
• if the command-line includes -u DEFAULTS recent versions of Vim will skip any vimrc but will load the defaults.vim (which sets 'nocompatible')
• In recent versions of Vim, --clean on the command-line is equivalent to -u DEFAULTS -U NONE -i NONE
• If the command-line includes -u NONE (with a lowercase u) Vim will look for neither a vimrc nor a defaults.vim; it will also not load global pugins. 'compatible' is then on by default (in the absence of a -N switch, see below)
• If the command-line includes -N Vim will start in 'nocompatible' mode even if no startup scripts are read
• If the command-line includes -C Vim will start in 'compatible' mode even if a vimrc is found (but a set nocompatible statement in a vimrc and/or a defaults.vim may change that).
• I'm not sure which of the above apply when starting Vim as ex, and what changes depending on the -s switch to ex (or to vim -e)

[lucianposton]

In my original repro steps, 'compatible' is set to on for ex -s according to :verbose set cp?.

With either echo "set nocompatible" > ~/.vimrc or with no ~/.vimrc, 'compatible' is set to on for ex -s, while it is set to off for ex (no -s). With echo "set compatible" > ~/.vimrc, 'compatible' is set to on for both ex and ex -s.

Both -N and -u DEFAULTS caused ex -s to turn off 'compatible', resulting in a success exit code as expected in the repro steps from my initial report.

It would appear that the underlying issue is ex -s ignores set nocompatible in .vimrc. Or is there a good reason for that behavior? Thoughts?

[tonymec]

Looks like ex -s does an accelerated startup, ignoring vimrc and defaults.vim unless explicitly told otherwise on the command-line.

I think this is intentional, to make batch-mode behaviour more reproducible (by implying -u NONE unless told otherwise). But it might be an oversight. @brammool : what do you think?

@lucianposton : if your batch script contains continuation lines, or if it otherwise relies on nocompatible being set, it's a good idea to start that script with a line saying set nocompatible.

[lucianposton]

Looks like ex -s does an accelerated startup, ignoring vimrc and defaults.vim unless explicitly told otherwise on the command-line.

I think this is intentional, to make batch-mode behaviour more reproducible (by implying -u NONE unless told otherwise). But it might be an oversight.

If indeed ex -s should ignore ~/.vimrc and defaults.vim, it seems odd to me that plugins would be loaded from .vim/plugin.

[brammool]

See :help -s-ex
This mode is mostly for backwards compatibility, using ex to execute a script.
Changing behavior would break those scripts.
It is indeed an odd mode. So don't use it :-).