Added support for iterable objects in {{#each}} helper (#1557)

* Added support for iterable object in {{#each}} helper
Currently {{#each}} helper supports either arrays, or objects,
however nowadays you can define custom iterable objects by overriding
a special method called Symbol.iterator, which results in empty result
being rendered.
* improved a test for iterables in {{#each}} returning empty result
* #each helper: using ES5 instead of generator functions in tests
* #each helper: using ES5 in the helper itself

lib/handlebars/helpers/each.js

@@ -49,6 +49,16 @@ export default function(instance) {
             execIteration(i, i, i === context.length - 1);
           }
         }
+      } else if (global.Symbol && context[global.Symbol.iterator]) {
+        const newContext = [];
+        const iterator = context[global.Symbol.iterator]();
+        for (let it = iterator.next(); !it.done; it = iterator.next()) {
+          newContext.push(it.value);
+        }
+        context = newContext;
+        for (let j = context.length; i < j; i++) {
+          execIteration(i, i, i === context.length - 1);
+        }
       } else {
         let priorKey;
 

spec/builtins.js

@@ -254,6 +254,37 @@ describe('builtin helpers', function() {
         template({});
       }, handlebarsEnv.Exception, 'Must pass iterator to #each');
     });
+
+    if (global.Symbol && global.Symbol.iterator) {
+      it('each on iterable', function() {
+        function Iterator(arr) {
+          this.arr = arr;
+          this.index = 0;
+        }
+        Iterator.prototype.next = function() {
+          var value = this.arr[this.index];
+          var done = this.index === this.arr.length;
+          if (!done) {
+            this.index++;
+          }
+          return { value: value, done: done };
+        };
+        function Iterable(arr) {
+          this.arr = arr;
+        }
+        Iterable.prototype[global.Symbol.iterator] = function() {
+          return new Iterator(this.arr);
+        };
+        var string = '{{#each goodbyes}}{{text}}! {{/each}}cruel {{world}}!';
+        var goodbyes = new Iterable([{text: 'goodbye'}, {text: 'Goodbye'}, {text: 'GOODBYE'}]);
+        var goodbyesEmpty = new Iterable([]);
+        var hash = {goodbyes: goodbyes, world: 'world'};
+        shouldCompileTo(string, hash, 'goodbye! Goodbye! GOODBYE! cruel world!',
+          'each with array argument iterates over the contents when not empty');
+        shouldCompileTo(string, {goodbyes: goodbyesEmpty, world: 'world'}, 'cruel world!',
+          'each with array argument ignores the contents when empty');
+      });
+    }
   });
 
   describe('#log', function() {