From b86c058803dc2705cf912dc63e216c7f7a41b0c8 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Mon, 6 Nov 2017 19:29:04 +1300
Subject: Refactor toggle_option_flag.vim

Got carried away and rewrote a lot of this all in one hit.

* Show single-line error messages with an s:Error() function
* Flag early errors on nonexistent options
* Test for the flag both before and after trying to toggle it to use as
the basis for error reporting and return value, in a new s:Has()
function
---
 vim/plugin/toggle_option_flag.vim | 81 ++++++++++++++++++++++++++++-----------
 1 file changed, 58 insertions(+), 23 deletions(-)

(limited to 'vim/plugin')

diff --git a/vim/plugin/toggle_option_flag.vim b/vim/plugin/toggle_option_flag.vim
index 1d4b11ce..dcc26cce 100644
--- a/vim/plugin/toggle_option_flag.vim
+++ b/vim/plugin/toggle_option_flag.vim
@@ -12,19 +12,16 @@ if exists('g:loaded_toggle_option_flag')
 endif
 let g:loaded_toggle_option_flag = 1
 
-" Internal function to do the toggling
-function! s:Toggle(option, flag, local)
-
-  " Check for weird options, we don't want to :execute anything funny
-  if a:option =~# '\m\L'
-    echoerr 'Illegal option name'
-    return
-  endif
+" Show an error-highlighted message and beep, but without a real :echoerr
+function! s:Error(message)
+  execute 'normal! \<Esc>'
+  echohl ErrorMsg
+  echomsg a:message
+  echohl None
+endfunction
 
-  " Choose which set command to use
-  let l:set = a:local
-        \ ? 'setlocal'
-        \ : 'set'
+" Test whether an option currently has a flag as part of its value
+function! s:Has(option, flag)
 
   " Horrible :execute to get the option's current setting into a variable
   " (I couldn't get {curly braces} indirection to work)
@@ -33,29 +30,67 @@ function! s:Toggle(option, flag, local)
 
   " If the flag we're toggling is longer than one character, this must by
   " necessity be a delimited option. I think all of those in VimL are
-  " comma-separated. Extend the flag and current setting so that they'll still
-  " match at the start and end. Otherwise, use them as-is.
+  " comma-separated. Extend the flag and value so that they'll still match at
+  " the start and end. Otherwise, use them as-is.
   if strlen(a:flag) > 1
     let l:search_flag = ',' . a:flag . ','
-    let l:search_current = ',' . l:current . ','
+    let l:search_value = ',' . l:current . ','
   else
     let l:search_flag = a:flag
-    let l:search_current = l:current
+    let l:search_value = l:current
   endif
 
+  " Return whether
+  return stridx(l:search_value, l:search_flag) > -1
+
+endfunction
+
+" Internal function to do the toggling
+function! s:Toggle(option, flag, local)
+
+  " Check for spurious option strings, we don't want to :execute anything funny
+  if a:option =~# '\m\L'
+    call s:Error('Illegal option name')
+    return 0
+  endif
+
+  " Check the option actually exists
+  if !exists('&' . a:option)
+    call s:Error('No such option: ' . a:option)
+    return 0
+  endif
+
+  " Choose which set command to use
+  let l:set = a:local
+        \ ? 'setlocal'
+        \ : 'set'
+
+  " Find whether the flag is set before the change
+  let l:before = s:Has(a:option, a:flag)
+
   " Assign -= or += as the operation to run based on whether the flag already
   " appears in the option value or not
-  let l:operation = stridx(l:search_current, l:search_flag) > -1
+  let l:operation = l:before
         \ ? '-='
         \ : '+='
 
-  " Build the command strings to set and then show the value
-  let l:cmd_set = l:set . ' ' . a:option . l:operation . escape(a:flag, '\ ')
-  let l:cmd_show = l:set . ' ' . a:option . '?'
+  " Try to set the option; suppress errors, we'll check our work
+  silent! execute l:set
+        \ . ' '
+        \ . a:option . l:operation . escape(a:flag, '\ ')
+
+  " Find whether the flag is set after the change
+  let l:after = s:Has(a:option, a:flag)
+
+  " If we made a difference, report the new value; if we didn't, admit it
+  if l:before != l:after
+    execute l:set . ' ' . a:option . '?'
+  else
+    call s:Error('Unable to toggle '.a:option.' flag '.a:flag)
+  endif
 
-  " Run the set and show command strings
-  execute l:cmd_set
-  execute l:cmd_show
+  " Return value is whether we made a change
+  return l:before != l:after
 
 endfunction
 
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