Automatically indent at the right level when moving to a completely empty line

Question

I have this binding in my .vimrc to trick autointent into actually populating the next line with real characters, so that if I hit enter, leave the line, and click back to it, I can already be at the indentation level of the surrounding code.

"Make autoindent insert actual characters instead of fake characters that go
"away if you move.
inoremap <CR> <CR><space><BS>

However, this leaves lines with trailing whitespace (enough spaces to indent to the level of the surrounding code), like this:

int.main().{
....int.a;
....
....int b;    
}

This lets me click on that blank line, hit i, start typing, and get code at the right indentation level.

Now I'm working on a project where the linter has a Strong Opinion that there should be no trailing spaces, even on blank lines that are, semantically, blank at a particular indentation level.

Can I keep the behavior of being able to click on the tail end of a line and have my cursor be at the right position to insert code on that line, but not fill the file with real trailing spaces? Is there a good way to bind i to automatically jump to the right indentation level when entering insert mode? Or is there another existing keybinding I should be using for "enter insert mode at the indentation level of surrounding code"?

Answer 1

I'd say the easiest way to insert text at the correct indentation is to use the o or O Normal-mode commands. From :help o:

When 'autoindent' is on, the indent for a new line is obtained from the previous line. When 'smartindent' or 'cindent' is on, the indent for a line is automatically adjusted for C programs.

Of course, these two commands will insert additional lines, so if you really wanted to replace the blank line, you might need to delete it with a separate command, either before or after performing the insertion. But I believe in some cases you might actually want to preserve the blank line, in which case these commands are a perfect fit.

---

One alternative is for you to keep inserting the extra whitespace into your buffer, but then strip them right before you save the file. You can do so with an autocmd:

autocmd BufWritePre * %s/\s\+$//e

This solution is more limited though, since now you can only jump to a previously indented line until you save the file, after which the whitespace that allowed you to use it will have been stripped.

You could consider a solution using 'virtualedit', which allows you to jump to any column of a line and start inserting at that position, having Vim insert the appropriate indent. But this solution isn't great either, since moving to a line will move you to any column of that line, not necessarily the last one, which is where your original indent ended. Using 'virtualedit' might also interfere with plug-ins or other editing commands you typically use.

So, in short, o and O seem to be the best fit. If you really find yourself often replacing the blank line rather than preserving it, then consider creating a mapping that will first delete it (perhaps checking that it's really empty before doing so) and then using one of the two commands to start editing where the now removed blank line was, but with the proper indentation.

Answer 2

I have remapped i (and other keys to enter insert mode) to run together with reindent command (:h i_CTRL-F).

noremap i i<c-f>

Note that in order for it to work, cindent (:h 'cindent') has to be enabled. You can turn it on for every filetype with autocmd:

autocmd FileType * set cindent