Using `emacsclient` for `$VISUAL` raises `End of file during parsing`

Question

I want to use emacs as VISUAL with server-mode. As a test, I write the following in a terminal:

emacsclient -F "((left . 0) (top . 0))" -c -n file

This behaves exactly as expected; it opens my file file in GUI window with the right geometry, exactly the behaviour I want from $VISUAL filename. So I add the following line to the end of my .bashrc:

export VISUAL='emacsclient -F "((left . 0) (top . 0))" -c -n file'

Now I test this from a terminal:

$ source .bashrc
$ $VISUAL file
*ERROR*: End of file during parsing

I recognize that as an error thrown by emacs when it evaluates elisp with mismatched delimiters. I thought at first that I might be doing something wrong with single and double quotes, but this doesn't explain the error; emacs is starting, but somewhere it's running into some problem with a mismatched delimiter.

Question: (1) Why is emacs throwing an error when called from $VISUAL like this, despite the fact that the command itself works correctly? (2) How do I fix it?

P.S. I'm on GNU Emacs 26.3 and GNU bash, version 5.0.17(1)-release (x86_64-pc-linux-gnu); thanks in advance for your help.

Answer 1

The problem is how the shell expands $VISUAL. When the shell expands a variable outside of double quotes ($VISUAL as opposed to "$VISUAL"), it splits the value into words (and treats each word as a shell wildcard pattern, but that's not relevant here). So it runs the command emacsclient with the arguments -F, "((left . 0), (top . 0))", -c, -n, file, file. The error message you're seeing comes from parsing "((left . 0) which is an unterminated string.

There's no standard for the syntax of VISUAL: some applications use the equivalent of running $VISUAL filename in a shell, while others use the equivalent of taking the value of VISUAL, appending the (quoted) file name and running the result through a shell (which would do what you want), and there are even other cases (I've seen applications that want VISUAL to be a path to an executable file with no arguments, but that's uncommon). So you should keep it simple. If you need to pass arguments with spaces, use a wrapper script.

In my configuration, I use

export VISUAL="$HOME/bin/EDITOR"

and I have a script called EDITOR that dispatches to emacslient (and for me also has a fallback if Emacs isn't installed). For you that wrapper script would be

#!/bin/sh
exec emacsclient -F "((left . 0) (top . 0))" -c -n "$@"