Add operator symbols in regex to show correct field highlight termination

[zkry]

Fixes #1849. This is indeed a problem even when gofmt is on (ex. inside array index brackets). This should cover all of the operators.

[fatih]

Hi @zkry

For this kind of PR's a before/after screenshot on what this is fixed is appreciated.

[zkry]

Oh, ok. Here is a screenshot showing a simple example of before and after the change.

[arp242]

Also, could you post the results from the benchmarks with ./scripts/bench-syntax? Then we have an idea how this will affect performance (it's already quite slow). Thanks!

[bhcleek]

@Carpetsmoker I benchmarked these changes against master; they end up slowing things down about 10%, but if this PR goes one step further and uses \%( where possible, then this PR and the use of \%( results in a zero net change in performance.

[zkry]

@bhcleek Thanks. I updated the PR with your suggestion. I was having trouble figuring out how to run the benchmark and get the relevant info. I'll write here when I can confirm that there is now slowdown.

[bhcleek]

@zkry you'll likely need to replace more \( with \%( than just that one place; when I tested there were a several places that I updated to use \%(....

[arp242]

This regular expression is now very hard to understand and/or maintain. It should probably documented better and split over multiple lines.

For example:

vim-go/syntax/go.vim

Lines 108 to 120 in b81a447

	" [n] notation is valid for specifying explicit argument indexes
	" 1. Match a literal % not preceded by a %.
	" 2. Match any number of -, #, 0, space, or +
	" 3. Match * or [n]* or any number or nothing before a .
	" 4. Match * or [n]* or any number or nothing after a .
	" 5. Match [n] or nothing before a verb
	" 6. Match a formatting verb
	syn match goFormatSpecifier /\
	\([^%]\(%%\)*\)\
	\@<=%[-#0 +]*\
	\%(\%(\%(\[\d\+\]\)\=\*\)\|\d\+\)\=\
	\%(\.\%(\%(\%(\[\d\+\]\)\=\*\)\|\d\+\)\=\)\=\
	\%(\[\d\+\]\)\=[vTtbcdoqxXUeEfFgGsp]/ contained containedin=goString,goRawString

(which is still not great, but better than this).

It may also be worth adding \v at the start of this pattern for readability.

[zkry]

That makes sense. I can clean this regex along with updating \( with \%(. Sorry for having stepped away from this issue for such a long time by the way.

[zkry]

I noticed how were weren't using the \1 - \9 feature of regexes at all so it seemed safe to update all instances of \( to \%(. It was a good idea to clean up the regex too. It would always take me forever to understand what it was doing.

[bhcleek]

Thanks, @zkry !