Why this function disable expandtab?

Question

I am trying to make a little function that aims to extract a method from a piece of php code. The function works fine. Is not optipized but "done is better than perfect" and the purpose here is not perfectio but just, ... keep expandtab settings right.

And here the incriminated code.

fun! ExtractMethod() range
    let g:selection = s:get_visual_selection()
    exec ":set paste"
    exec ":normal! Gko\<esc>o\<esc>Spublic function xxxxxxx()\<esc>=="
    exec ":normal! o\t{\<esc>"
    exec ":normal! o" . g:selection . "\<esc>"
    exec ":normal! o\t}\<esc>%k2w"
endfun
function! s:get_visual_selection()
    let [lnum1, col1] = getpos("'<")[1:2]
    let [lnum2, col2] = getpos("'>")[1:2]
    let lines = getline(lnum1, lnum2)
    let lines[-1] = lines[-1][: col2 - 2]
    let lines[0] = lines[0][col1 - 1:]
    return join(lines, "\n")
endfunction
vnoremap <Leader>r :call ExtractMethod()<cr>

Answer 1

From :h paste:

When the 'paste' option is switched on (also when it was already on):
        - mapping in Insert mode and Command-line mode is disabled
        - abbreviations are disabled
        - 'autoindent' is reset
        - 'expandtab' is reset
        - 'formatoptions' is used like it is empty
        - 'revins' is reset
        - 'ruler' is reset
        - 'showmatch' is reset
        - 'smartindent' is reset
        - 'smarttab' is reset
        - 'softtabstop' is set to 0
        - 'textwidth' is set to 0
        - 'wrapmargin' is set to 0
These options keep their value, but their effect is disabled:
        - 'cindent'
        - 'indentexpr'
        - 'lisp'
...
When the 'paste' option is reset the mentioned options are restored to
the value before the moment 'paste' was switched from off to on.

So, reset paste at the end of your function:

fun! ExtractMethod() range
    let g:selection = s:get_visual_selection()
    set paste
    exec ":normal! Gko\<esc>o\<esc>Spublic function xxxxxxx()\<esc>=="
    exec ":normal! o\t{\<esc>"
    exec ":normal! o" . g:selection . "\<esc>"
    exec ":normal! o\t}\<esc>%k2w"
    set nopaste
endfun