fix indentation of python code in vim

fixindent.vim

function! AlignWithTopLine() range
    " Handle case when selection is at the start of the file
    if a:firstline <= 1
        " If at the start of file, use default indentation (0)
        let reference_indent = 0
        let above_line = ""
    else
        " Find the first non-empty line above the selection
        let above_line_num = a:firstline - 1
        while above_line_num >= 1 && getline(above_line_num) =~ '^\s*$'
            let above_line_num = above_line_num - 1
        endwhile
        
        " If we couldn't find a non-empty line, use default indentation
        if above_line_num < 1
            let reference_indent = 0
            let above_line = ""
        else
            let above_line = getline(above_line_num)
            let reference_indent = indent(above_line_num)
        endif
    endif
    
    " Check characteristics of the line above (if it exists)
    let ends_with_colon = !empty(above_line) && above_line =~# ':$'
    let starts_with_special = !empty(above_line) && above_line =~# '^\s*\(with\|await\|if\|for\|while\|def\|class\)'
    let is_continuation = !empty(above_line) && above_line =~# '\((\|\[\|{\).*\(,\|\\\)$'
    
    " Determine target indentation
    let target_indent = reference_indent
    
    " Handle different cases for alignment
    if ends_with_colon || starts_with_special
        " For block starts or special constructs, add one level of indentation
        let target_indent = reference_indent + &shiftwidth
    elseif is_continuation
        " For line continuations (ending with comma or backslash), align with extra indent
        let target_indent = reference_indent + &shiftwidth
    endif
    
    " Get the first line's current indentation as reference for relative shifts
    let first_line = getline(a:firstline)
    let first_line_indent = indent(a:firstline)
    let first_line_content = substitute(first_line, '^\s*', '', '')
    
    " Check if the first line of selection is a continuation of a previous statement
    let first_line_is_continuation = !empty(above_line) && 
                                   \ (above_line =~# '\((\|\[\|{\|\\$\|,$\)' && 
                                   \ first_line_content !~# '^\()\|]\|}\)')
    
    " Calculate the indentation shift needed
    let indent_shift = 0
    if first_line_is_continuation
        let indent_shift = target_indent - first_line_indent
    else
        let indent_shift = target_indent - first_line_indent
    endif
    
    " Apply the indentation to all lines in the selection
    for lineno in range(a:firstline, a:lastline)
        let line = getline(lineno)
        let current_indent = indent(lineno)
        let current_line_content = substitute(line, '^\s*', '', '')
        
        " Skip empty lines
        if current_line_content == ''
            continue
        endif
        
        " Calculate new indentation preserving relative structure
        let new_indent = current_indent + indent_shift
        
        " Special handling for closing brackets/braces/parentheses
        if current_line_content =~# '^\()\|]\|}\)'
            " Closing brackets align with the opening line (one level back)
            let new_indent = max([0, target_indent - &shiftwidth])
        endif
        
        " Ensure indentation is never negative
        let new_indent = max([0, new_indent])
        
        " Create the new line with proper indentation
        let new_line = repeat(' ', new_indent) . current_line_content
        
        call setline(lineno, new_line)
    endfor
endfunction

function! ConditionalAlign()
    if &filetype == 'python'
        " Store the original selection boundaries
        let l:start_line = a:firstline
        let l:end_line = a:lastline
        
        " Apply indent to the selection. autopep8 will not align if 
        " with xx: 
        " dosomethin 
        " if there are not indentation 
        norm gv4>
        
        " Run autopep8 on the selection, assume indentation = 0 
        silent execute l:start_line . ',' . l:end_line . '!autopep8 -'
        " Re-indent to above line
        
        silent execute l:start_line . ',' . l:end_line . 'call AlignWithTopLine()'
    else
        normal! gv=
    endif
endfunction

vnoremap = :'<,'>call ConditionalAlign()<CR>

thanks for sharing this. daily neovim user here, and coming from many different languages i often use == to format the indentation of the current line, and i've been having the worst time working with python files. using the native vim / neovim indentexpr is not that great nor is the indentexpr provided treesitter that much better. and i tried using ruff to try and format a few visually selected lines, but apparently that can only format the entire file, not what i'm looking for.

do you still actively use this? or have you moved on to something else? thanks again for sharing 🙏