widgets for case manipulation: `gU` in normal and `U` in visual mode

I reckon there's already a widget for the g~ action in zle. So g~iw will invert the case of a word.

I read the zshzle manual and did not find a widget that would give me the behaviour of gU (capitalize action) in vim.

for example: for the word "path_variable", with the cursor on the v, gUiW would change the world to "PATH_VARIABLE", and so on and so forth.

the widget capitalize-word does not seem to be the answer. I've tested it.

I also found that the key U in visual mode does not capitalize the visually selected text/region. I did not find a widget in the manual that would give me the desired behaviour either.

Is this a matter of writing a custom widget, or would one have to submit a patch upstream with c code changes? How can I bind gU in normal and U in visual mode to achieve the desired behaviour in zle vi-mode?

ZSH 5.3 will have pre built widgets for that. But if you can't wait, here it is:

# credits go to Oliver Kiddle <opk@zsh.org>,
# who personally shared these upper/lower widgets.
# I just corrected a small bug.
vi-lowercase() {
  local save_cut="$CUTBUFFER"
  local save_cur="$CURSOR"

  zle .vi-change || return
  zle .vi-cmd-mode

  CUTBUFFER="${CUTBUFFER:l}"

  if [[ $CURSOR = '0' ]]; then
    zle .vi-put-before -n 1
  else
    zle .vi-put-after -n 1
  fi

  CUTBUFFER="$save_cut" 
  CURSOR="$save_cur"
}

vi-uppercase() {
  local save_cut="$CUTBUFFER" 
  local save_cur="$CURSOR"

  zle .vi-change || return
  zle .vi-cmd-mode

  CUTBUFFER="${CUTBUFFER:u}"

  if [[ $CURSOR = '0' ]]; then
    zle .vi-put-before -n 1
  else
    zle .vi-put-after -n 1
  fi

  CUTBUFFER="$save_cut" 
  CURSOR="$save_cur"
}

# can safely disable this after commit zsh commit #a73ae70 (zsh-5.2-301-    ga73ae70)
zle -N vi-lowercase
zle -N vi-uppercase
bindkey -a 'gU' vi-uppercase
bindkey -a 'gu' vi-lowercase
bindkey -M visual 'u' vi-lowercase
bindkey -M visual 'U' vi-uppercase