Line text objects for selecting line with and without indents

[sudormrfbin]

Would it be reasonable to request the following as an addition to the Match mode?

mal identical to x (maybe include prepended indentation)
mil identical to x_

The mnemonics in Helix are really good and adding these makes sense IMO.

Originally posted by @superDuperCyberTechno in #4225 (comment)

[sudormrfbin]

Copy pasting my comment from the discussion:

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These exact keybinds have been on my mind for some time, with the difference that mal would select the line without the ending newline (whereas x selects with the new line).

Another idea would be to have:

1. alt-x as x_ (which removes indentation and newline from selection) and alt-X as x without newline (keeping indentation intact).

   This would require moving the shrink_to_line_bounds keybind from alt-x to some other key, but makes it easier to do things like alt-x c to mimic vim's cc.

2. Or we could move shrink_to_line_bounds from alt-x to alt-X (which pairs with extend_to_line_bounds that is actually on X) and have only x_ bound to alt-x.

[sudormrfbin]

The main selling point I see is for doing things like "change current line" where you might want to keep the line's current indentation but change the text (which means x cannot be used) or delete everything but put the cursor on the same line in insert mode. x will select the whole line (including newline) so xc will delete all of the line and put the cursor on the start of the next line, which is undesirable here. x_ does the job but something like mil is easier to grok.

[taupiqueur]

There is a good rationale from @Delapouite for introducing line text objects: https://github.com/Delapouite/kakoune-text-objects

[raffimolero]

here's a bind for now.
EDIT: this uh, removes all the other "match in" and "match around" commands...

[keys.normal]
m.i.l = ["goto_first_nonwhitespace", "select_mode", "goto_line_end", "normal_mode"]
m.a.l = ["goto_line_start", "select_mode", "goto_line_end", "normal_mode"]

on a similar note, can we switch x with X by default? i find extend_to_line_bounds a more common operation than extend_line_below. there must be an existing discussion for this somewhere.

i'd find it easier to delete empty lines if i didn't have to either

1. remember that xd on empty lines deletes two lines, or
2. use Xd which requires me to release shift for d by default.

this can also be solved by also making D delete, which is my current config, which lets me hold right shift to type XD, or by rendering newlines and just keeping track.