Ctrl-W in insert mode erases only up to where insert was started

Question

I frequently use <C-w> in insert mode to back up when I mistype things. I've noticed some odd behavior if I start insert mode when in the middle of a word.

For example, if I have the following line (cursor location indicated by ^):

I love to use CamelCase
                   ^

When I am at that cursor location and do the key combination i<End><C-w>, I am left with the following:

I love to use Camel
                   ^

I expected that <C-w> would erase up to the beginning of CamelCase since that is a word. Is <C-w> only supposed to erase up to the beginning of where I started inserting? Or is there some setting I have to flip to get it to delete the entire word?

If I press <C-w> again, it does erase the rest of the word. I just wasn't expecting a word boundary to appear where insert mode started.

This is using Vim 8.1 (2018 May 18) for Windows.

Answer 1

This is documented behaviour. Deleting text before the insert start location is controlled by the 'backspace' option, and :help 'backspace' says this:

start: allow backspacing over the start of insert; CTRL-W and CTRL-U stop once at the start of insert.

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If you really want <C-w> to behave as you "expect", here's a convoluted mapping (the different handling depending on whether the cursor is at the end of the line or not is to make sure that the last character is handled correctly: if you do db when the cursor is at the end of the line, the last character is not deleted; if you do vbd when the cursor is not at the end of the line, the following character is deleted):

inoremap <expr> <C-w> col('.') == len(getline('.'))+1 ? "\<C-o>vb\"_d" : "\<C-o>\"_db"

Answer 2

As of Vim patch 8.2.0590 you can use :set backspace+=nostop to make backspace and CtrlW not stop at the insertion point.

Answer 3

An easier remap for <c-w> is:

ino <c-w> <c-\><c-o>i<c-w>

Note that this also moves the insert start location, which may changes the behavior of <c-u> or <bs> (depends on 'backspace' option)