fixing twigjs#737 make sure that ternary expression does not change c…

…ontext + exporting functions for test purposes

src/twig.exports.js

@@ -227,6 +227,9 @@ module.exports = function (Twig) {
     // Export our tests.
     Twig.exports.tests = Twig.tests;
 
+    // Export our functions.
+    Twig.exports.functions = Twig.functions;
+
     Twig.exports.Promise = Twig.Promise;
 
     return Twig;

src/twig.expression.operator.js

@@ -172,7 +172,7 @@ module.exports = function (Twig) {
                 a = a.length;
             }
 
-            if (b && Array.isArray(b)) {
+            if (operator !== '?' && (b && Array.isArray(b))) {
                 b = b.length;
             }
         }

test/test.expressions.js

@@ -361,6 +361,13 @@ describe('Twig.js Expressions ->', function () {
             testTemplate.render({test: undefined}).should.equal('false');
         });
 
+        it('should not override context', function () {
+            const str = `{% set classes = ['a', 'b'] %}{% set classes = classes ? classes|merge(['c']) : '' %}{{ dump(classes) }}`;
+            const expected = Twig.functions.dump(['a', 'b', 'c']);
+            const testTemplate = twig({data: str});
+            testTemplate.render().should.equal(expected);
+        });
+
         it('should support in/containment functionality for arrays', function () {
             let testTemplate;