Delete from cursor to the beginning of a line in insert mode

Question

In insert mode I want to delete all text from the cursor to the beginning of a line and stay in insert mode.

Here is the mapping I tried:

inoremap DD <ESC>c0

and this almost works. In the following line (in insert mode)

This is a test line 
              ^
           cursor

in insert mode cursor goes 1 step further than just typed symbol (t in my case). And if I press DD, I will get

t line

but want just

 line
^
cursor

with the space the cursor pointed.

Is there a way to do this in vim?

Answer 1

There's actually already a builtin for this. :h i_<C-u>:

                *i_CTRL-U*
CTRL-U          Delete all entered characters in the current line (see
    |i_backspacing| about joining lines).

You could map this, e.g.

inoremap DD <C-u>

But this might interfere with typing. I would encourage you to just learn to use <C-u> instead.