How to add inline comment for the echo command?

Question

I've tried the following syntax:

:echo 123 " comment

but it failed with E15 and E114 errors.

Is there any way to put the inline comment right after the command, so it can be ignored?

Answer 1

The problem with this is, echo is expecting an expression. You can read what an expression is at :h expression in great detail. In short this means, :echo expects either a variable or a string (which is either single quoted or double quoted).

Now look at your command, you are echoing the number 123 and start with a double-quoted string. However, "forgot" the closing quotation marks, so Vim is complaining.

A workaround is, to actually start an empty command, e.g. this works:

:echo 1234 | " put your comment here

Answer 2

from :h :echo (note the last line):

                                                        :ec :echo
:ec[ho] {expr1} ..      Echoes each {expr1}, with a space in between.  The
                        first {expr1} starts on a new line.
                        Also see :comment.
                        Use "\n" to start a new line.  Use "\r" to move the
                        cursor to the first column.
                        Uses the highlighting set by the :echohl command.
                        Cannot be followed by a comment.

Also potentially of interest, from :h comment (note the last paragraph):

                                                        :quote :comment
'"' at the start of a line causes the whole line to be ignored.  '"'
after a command causes the rest of the line to be ignored.  This can be used
to add comments.  Example:
        :set ai         "set 'autoindent' option
It is not possible to add a comment to a shell command ":!cmd" or to the
":map" command and a few others, because they see the '"' as part of their
argument.  This is mentioned where the command is explained.