error on execute() when triggered from modeline in neovim

[asdfzdfj]

sample error text (slightly edited for readability):

Error detected while processing modelines[2075]
..OptionSet Autocommands for "tabstop"
..function indent_guides#process_autocmds[2]
..indent_guides#enable[8]
..indent_guides#init_script_vars[7]
..indent_guides#capture_highlight:
line    1:
E12: Command not allowed from exrc/vimrc in current dir or tag search
E12: Command not allowed from exrc/vimrc in current dir or tag search
E12: Command not allowed from exrc/vimrc in current dir or tag search

steps to reproduce (approx).:

1. start nvim with this plugin and modeline enabled
2. open a file containing modeline (by :e command)

looks like when this plugin is triggered from OptionSet event via modeline, it is run inside sandbox where indent_guides#capture_highlight() function errors out because execute() function is not allowed inside sandbox.

vim-indent-guides/autoload/indent_guides.vim

Lines 255 to 259 in 9a106c7

	function! indent_guides#capture_highlight(group_name) abort
	let l:output = execute('hi ' . a:group_name, 'silent')
	let l:output = substitute(l:output, '\n', '', '')
	return l:output
	endfunction

one possible solution is to use some function like synIDattr() and related functions (synIDtrans(), hlID()) to directly query any needed highlight color values instead of execute()ing and parsing :highlight output.
those functions exists in regular vim for quite some time and appears to be sandbox safe, so it should be safe to use.

[huyz]

I get a similar error when I open help in neovim 0.10.0:

Error detected while processing modelines[272]..OptionSet Autocommands for "tabstop"..function indent_guides#process_autoc
mds[2]..indent_guides#enable[8]..indent_guides#init_script_vars[7]..indent_guides#capture_highlight:
line    1:
E12: Command not allowed in secure mode in current dir or tag search
E12: Command not allowed in secure mode in current dir or tag search

PR #158 does fix my problem.