E474: Invalid argument: diffopt+=internal,algorithm:patience on Vim 8.1 on MacOS

[agude]

Here is the error:

Error detected while processing /Users/agude/.vimrc:
line  433:
E474: Invalid argument: diffopt+=internal,algorithm:patience
This script requires vim7.0+ with Python 3.6 support.

Here is the version info:

VIM - Vi IMproved 8.1 (2018 May 18, compiled Feb 29 2020 00:47:39)
macOS version
Included patches: 1-503, 505-680, 682-2292
Compiled by [email protected]
Normal version without GUI.  Features included (+) or not (-):
+acl               -farsi             -mouse_sysmouse    -tag_any_white
-arabic            +file_in_path      -mouse_urxvt       -tcl
+autocmd           +find_in_path      +mouse_xterm       -termguicolors
+autochdir         +float             +multi_byte        +terminal
-autoservername    +folding           +multi_lang        +terminfo
-balloon_eval      -footer            -mzscheme          +termresponse
-balloon_eval_term +fork()            +netbeans_intg     +textobjects
-browse            -gettext           +num64             +textprop
+builtin_terms     -hangul_input      +packages          +timers
+byte_offset       +iconv             +path_extra        +title
+channel           +insert_expand     -perl              -toolbar
+cindent           +job               +persistent_undo   +user_commands
-clientserver      +jumplist          +postscript        -vartabs
+clipboard         -keymap            +printer           +vertsplit
+cmdline_compl     +lambda            -profile           +virtualedit
+cmdline_hist      -langmap           +python/dyn        +visual
+cmdline_info      +libcall           -python3           +visualextra
+comments          +linebreak         +quickfix          +viminfo
-conceal           +lispindent        +reltime           +vreplace
+cryptv            +listcmds          -rightleft         +wildignore
+cscope            +localmap          +ruby/dyn          +wildmenu
+cursorbind        -lua               +scrollbind        +windows
+cursorshape       +menu              +signs             +writebackup
+dialog_con        +mksession         +smartindent       -X11
+diff              +modify_fname      -sound             -xfontset
+digraphs          +mouse             +spell             -xim
-dnd               -mouseshape        +startuptime       -xpm
-ebcdic            -mouse_dec         +statusline        -xsmp
-emacs_tags        -mouse_gpm         -sun_workshop      -xterm_clipboard
+eval              -mouse_jsbterm     +syntax            -xterm_save
+ex_extra          -mouse_netterm     +tag_binary
+extra_search      +mouse_sgr         -tag_old_static
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H   -DMACOS_X_UNIX  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc   -L/usr/local/lib -o vim        -lm -lncurses  -liconv -framework Cocoa

I believed patch-8.1.0360 was the right one to check. Perhaps not?

Originally added to Vim here: vim/vim#2732

[chaoren]

Hi, found this after searching for the same issue. I'll write down my findings here for anyone else searching about this problem.

patch-8.1.0360 is indeed the right patch for has(), but the problem is that Apple actually removed xdiff while compiling a version of vim that's supposed to include the patch.

If you look at :h diffexpr, you'll see that they actually have the changes from patch-8.1.0360.
If you look at :h diffopt, you'll see that they do not have the changes from patch-8.1.0360.

This other issue I found has the same root cause:

In short: stock vim on Catalina does not support diffopt=internal even though the default options include internal.

Apple removed the internal option item from diffopt (probably while trying to remove xdiff), but didn't remove internal from the default value of diffopt.

Now why would Apple want to remove xdiff? Because of https://github.com/vim/vim/blob/master/src/xdiff/COPYING:

		  GNU LESSER GENERAL PUBLIC LICENSE
		       Version 2.1, February 1999

 Copyright (C) 1991, 1999 Free Software Foundation, Inc.
     59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

What's the solution then?

I have this in my vimrc now. Since this issue is specific to the default vim distributed on Mac, I've decided to just hard code that condition. Also handles the issue of internal preventing other option items being added or removed.

if has('mac') && $VIM == '/usr/share/vim'
	set diffopt-=internal
elseif has('patch-8.1.0360')
	set diffopt+=algorithm:patience
endif

I only ran into this issue while using sudo -e, since I usually use Homebrew vim. Apparently sudo -e uses the system vim.

[agude]

@chaoren Thanks a ton for the research! 😄

This will fix an annoyance that has been bugging me for over a year now!