Fix: attach annotation to static part of rule ref

Previously, annotations were missing on rules that had variable
components in the ref head. Now we annotate the rule using the
path up to the first var.

Fixes open-policy-agent#7050

Signed-off-by: Anders Eknert <anders@styra.com>

ast/annotations.go

@@ -520,7 +520,7 @@ func attachRuleAnnotations(mod *Module) {
 		var j int
 		var found bool
 		for i, a := range cpy {
-			if rule.Ref().Equal(a.GetTargetPath()) {
+			if rule.Ref().GroundPrefix().Equal(a.GetTargetPath()) {
 				if a.Scope == annotationScopeDocument {
 					rule.Annotations = append(rule.Annotations, a)
 				} else if a.Scope == annotationScopeRule && rule.Loc().Row > a.Location.Row {

ast/parser_test.go

@@ -5785,6 +5785,23 @@ p contains 2
 				},
 			},
 		},
+		{
+			note: "rule with variable in ref head",
+			module: `package test
+
+# METADATA
+# title: foo
+rule[x] := true if x := 1
+			`,
+			expAnnotations: map[int][]*Annotations{
+				5: {
+					{
+						Scope: "rule",
+						Title: "foo",
+					},
+				},
+			},
+		},
 	}
 
 	for _, tc := range tests {