Python3 not built in through Homebrew

[dmcinnes]

I originally used --with-python3 but I see that switch is deprecated.

Output from my install command has --enable-python3interp:

$ brew install macvim --with-override-system-vim --with-lua
==> Downloading https://github.com/macvim-dev/macvim/archive/snapshot-146.tar.gz
Already downloaded: /Users/dmcinnes/Library/Caches/Homebrew/macvim-8.0-146.tar.gz
==> ./configure --with-features=huge --enable-multibyte --with-macarchs=x86_64 --enable-perlinterp --enable-rubyinterp --enable-tclinterp --enable-terminal --with-tlib=ncurses --with-compiledby=Homebrew --with-local-dir=/usr/local --enable-cscope --enable-luainterp --with-lua-prefix=/usr/local/opt/lua --enable-python3interp
==> make
🍺  /usr/local/Cellar/macvim/8.0-146: 2,161 files, 34.3MB, built in 1 minute 5 seconds

Though my :version has both -python and -python3:

:version
VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Mar 27 2018 16:28:08)
macOS version
Included patches: 1-1633
Compiled by Homebrew
Huge version with MacVim GUI.  Features included (+) or not (-):
+acl               +channel           +cryptv            +emacs_tags        -footer            +keymap            +menu              +mouse_sgr         +odbeditor         -python3           +statusline        +terminfo          +virtualedit       -X11
+arabic            +cindent           +cscope            +eval              +fork()            +lambda            +mksession         -mouse_sysmouse    +packages          +quickfix          -sun_workshop      +termresponse      +visual            -xfontset
+autocmd           +clientserver      +cursorbind        +ex_extra          +fullscreen        +langmap           +modify_fname      +mouse_urxvt       +path_extra        +reltime           +syntax            +textobjects       +visualextra       +xim
-autoservername    +clipboard         +cursorshape       +extra_search      -gettext           +libcall           +mouse             +mouse_xterm       +perl              +rightleft         +tag_binary        +timers            +viminfo           -xpm
+balloon_eval      +cmdline_compl     +dialog_con_gui    +farsi             -hangul_input      +linebreak         +mouseshape        +multi_byte        +persistent_undo   +ruby              +tag_old_static    +title             +vreplace          -xsmp
+balloon_eval_term +cmdline_hist      +diff              +file_in_path      +iconv             +lispindent        +mouse_dec         +multi_lang        +postscript        +scrollbind        -tag_any_white     +toolbar           +wildignore        -xterm_clipboard
+browse            +cmdline_info      +digraphs          +find_in_path      +insert_expand     +listcmds          -mouse_gpm         -mzscheme          +printer           +signs             +tcl               +transparency      +wildmenu          -xterm_save
++builtin_terms    +comments          +dnd               +float             +job               +localmap          -mouse_jsbterm     +netbeans_intg     +profile           +smartindent       +termguicolors     +user_commands     +windows
+byte_offset       +conceal           -ebcdic            +folding           +jumplist          +lua               +mouse_netterm     +num64             -python            +startuptime       +terminal          +vertsplit         +writebackup
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "$VIM/gvimrc"
    user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
    system menu file: "$VIMRUNTIME/menu.vim"
  fall-back for $VIM: "/Applications/MacVim.app/Contents/Resources/vim"
Compilation: clang -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_MACVIM -Wall -Wno-unknown-pragmas -pipe  -DMACOS_X -DMACOS_X_DARWIN  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: clang   -L.             -L /BuildRoot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.Internal.sdk/usr/local/libressl/lib -L/BuildRoot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX
10.13.Internal.sdk/usr/local/lib -L.             -L /BuildRoot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.Internal.sdk/usr/local/libressl/lib -L/BuildRoot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Devel
oper/SDKs/MacOSX10.13.Internal.sdk/usr/local/lib  -L/usr/local/lib -o Vim -framework Cocoa -framework Carbon       -lm  -lncurses -liconv -framework AppKit  -L/usr/local/opt/lua/lib -llua -fstack-protector  -L/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE -lperl   -F/S
ystem/Library/Frameworks -framework Tcl -framework CoreFoundation -framework Ruby   

Based on this change in the formula, Python3 should be built by default. Perhaps this is because depends_on "python3" is missing?

[splhack]

You should ask the maintainer of the formula instead of here.

Anyway I recommend you to use the official MacVim formula https://github.com/macvim-dev/homebrew-macvim which I only support.