How to convert this vim-plug configuration to packer.nvim

[Oatall]

function! BuildComposer(info)
  if a:info.status != 'unchanged' || a:info.force
    if has('nvim')
      !cargo build --release --locked
    else
      !cargo build --release --locked --no-default-features --features json-rpc
    endif
  endif
endfunction

Plug 'euclio/vim-markdown-composer', { 'do': function('BuildComposer') }

What is a:info.status in packer.nvim

[bryant-the-coder]

PackerStatus?