Add explicitPartialContext compiler flag

Fixes #1032

lib/handlebars/compiler/compiler.js

@@ -177,7 +177,11 @@ Compiler.prototype = {
     if (params.length > 1) {
       throw new Exception('Unsupported number of partial arguments: ' + params.length, partial);
     } else if (!params.length) {
-      params.push({type: 'PathExpression', parts: [], depth: 0});
+      if (this.options.explicitPartialContext) {
+        this.opcode('pushLiteral', 'undefined');
+      } else {
+        params.push({type: 'PathExpression', parts: [], depth: 0});
+      }
     }
 
     let partialName = partial.name.original,

spec/partials.js

@@ -41,6 +41,21 @@ describe('partials', function() {
                     'Partials can be passed a context');
   });
 
+  it('partials with no context', function() {
+    var partial = '{{name}} ({{url}}) ';
+    var hash = {dudes: [{name: 'Yehuda', url: 'http://yehuda'}, {name: 'Alan', url: 'http://alan'}]};
+    shouldCompileToWithPartials(
+        'Dudes: {{#dudes}}{{>dude}}{{/dudes}}',
+        [hash, {}, {dude: partial}, {explicitPartialContext: true}],
+        true,
+        'Dudes:  ()  () ');
+    shouldCompileToWithPartials(
+        'Dudes: {{#dudes}}{{>dude name="foo"}}{{/dudes}}',
+        [hash, {}, {dude: partial}, {explicitPartialContext: true}],
+        true,
+        'Dudes: foo () foo () ');
+  });
+
   it('partials with string context', function() {
     var string = 'Dudes: {{>dude "dudes"}}';
     var partial = '{{.}}';