Multiple @ in a transformation line are confused as the start of a new metavariable declaration

[JonathonReinhart]

Sorry for the confusing title, I'm trying to use the terminology from the grammar.

An example:

// a metavariable declaration (or just rule)
@ rule @
expression x, y
position p1, p2
@@

// transformation section
// note there are two @ in this line
foo(x@p1, y@p2)

// another metavariable declaration
// cocci.vim doesn't recognize this as a CocciGroup region
@@
expression foo
@@

(Note that when writing this issue, I marked this code fence as cocci, and whatever syntax highlighter GitHub uses seemed to highlight this correctly.)

As you can see in this image, cocci.vim thinks that the two @ are part of a metavariable declaration (rule):

However, if we require that the metavariable declaration (rule) @ start at the beginning of the line...

diff --git a/syntax/cocci.vim b/syntax/cocci.vim
index 9bf7a98..b5bc2d9 100644
--- a/syntax/cocci.vim
+++ b/syntax/cocci.vim
@@ -14,7 +14,7 @@ syn keyword CocciKeywords       statement function local list fresh position ide
 syn keyword CocciKeywords       declaration declarer attribute symbol format assignment contained
 syn keyword CocciKeywords       operator global field initializer initialiser iterator name contained
 
-syn region CocciGroup matchgroup=CocciGroupDelim start="@[^@]*@" end="@@" contains=CocciKeywords
+syn region CocciGroup matchgroup=CocciGroupDelim start="^@[^@]*@" end="^@@" contains=CocciKeywords
 
 syn match CocciLineRemoved      "^-.*"
 syn match CocciLineAdded        "^+.*"

...then everything looks fine:

It's not clear to me from looking at the grammar if the @ has to start at the beginning of a line (I've never been good wtih BNF). However, every Coccinelle example I've ever seen is as such.

[JonathonReinhart]

BTW as to what GitHub uses, I followed this trail:

• https://stackoverflow.com/a/8886392
• https://github.com/github/linguist/blob/master/lib/linguist/languages.yml
• https://github.com/github/linguist/blob/master/vendor/README.md
• https://github.com/Alhadis/language-etc/blob/master/grammars/smpl.cson

It looks like their definition does indeed anchor the metavariables @ at the beginning of the line:

	# Metavariables for transformations
	metavariables:
		name:  "meta.diff.header.metavariables.smpl"
		begin: "^(@).*(@)\\s*$"
		end:   "^(@@)"

Also worth noting that they do allow an @ in the rule name, where you exclude @.

[ahf]

Nice catch, I agree we should get this fixed. Would you be up for creating a pull request with your suggested change?