disallow empty attribute names in query language (#108)

Author: MarkKoester

grammar.pegjs

@@ -59,7 +59,9 @@ attr
   = "[" _ v:attrValue _ "]" { return v; }
   attrOps = a:[><!]? "=" { return (a || '') + '='; } / [><]
   attrEqOps = a:"!"? "="  { return (a || '') + '='; }
-  attrName = i:(identifierName / ".")+ { return i.join(''); }
+  attrName = a:identifierName as:("." identifierName)* {
+    return [].concat.apply([a], as).join('');
+  }
   attrValue
     = name:attrName _ op:attrEqOps _ value:(type / regex) {
       return { type: 'attribute', name: name, operator: op, value: value };

tests/queryAttribute.js

@@ -57,14 +57,6 @@ describe('Attribute query', function () {
         ]);
     });
 
-    // Not sure what AST would be producing an empty string, so
-    //  just checking this acceptable grammar doesn't fail and is
-    //  covered.
-    it('literal with empty string and dot', function () {
-        const matches = esquery(literal, 'Literal[.value=\'abc\']');
-        assert.lengthOf(matches, 0);
-    });
-
     it('literal with backslashes', function () {
         const matches = esquery(literal, 'Literal[value="\\z"]');
         assert.includeMembers(matches, [