Added support for Promises in #with (closes #469).

packages/blaze/builtins.js

@@ -16,17 +16,9 @@ Blaze._calculateCondition = function (cond) {
 Blaze.With = function (data, contentFunc) {
   const view = Blaze.View('with', contentFunc);
 
-  view.dataVar = new ReactiveVar();
-
-  view.onViewCreated(function () {
-    if (typeof data === 'function') {
-      // `data` is a reactive function
-      view.autorun(function () {
-        view.dataVar.set(data());
-      }, view.parentView, 'setData');
-    } else {
-      view.dataVar.set(data);
-    }
+  view.dataVar = null;
+  view.onViewCreated(() => {
+    view.dataVar = _createBinding(view, data, 'setData');
   });
 
   return view;

packages/blaze/lookup.js

@@ -278,8 +278,8 @@ Blaze._parentData = function (height, _functionWrapped) {
   if (! theWith)
     return null;
   if (_functionWrapped)
-    return function () { return theWith.dataVar.get(); };
-  return theWith.dataVar.get();
+    return function () { return theWith.dataVar.get()?.value; };
+  return theWith.dataVar.get()?.value;
 };
 
 

packages/blaze/view.js

@@ -792,7 +792,7 @@ Blaze.getData = function (elementOrView) {
     throw new Error("Expected DOM element or View");
   }
 
-  return theWith ? theWith.dataVar.get() : null;
+  return theWith ? theWith.dataVar.get()?.value : null;
 };
 
 // For back-compat

packages/spacebars-tests/async_tests.html

@@ -105,3 +105,7 @@
 <template name="spacebars_async_tests_each_new">
   {{#each y in x}}{{y}}{{else}}0{{/each}}
 </template>
+
+<template name="spacebars_async_tests_with">
+  {{#with x}}{{y}}{{/with}}
+</template>

packages/spacebars-tests/async_tests.js

@@ -11,12 +11,15 @@ function asyncTest(templateName, testName, fn) {
 }
 
 function asyncSuite(templateName, cases) {
-  for (const [testName, helpers, before, after] of cases) {
+  for (const [testName, helpers, before, after, cycles = 1] of cases) {
     asyncTest(templateName, testName, async (test, template, render) => {
       template.helpers(helpers);
       const readHTML = render();
-      test.equal(readHTML(), before);
-      await new Promise(Tracker.afterFlush);
+      // Some test cases require more cycles to propagate.
+      for (let cycle = 0; cycle < cycles; ++cycle) {
+        test.equal(readHTML(), before);
+        await new Promise(Tracker.afterFlush);
+      }
       test.equal(readHTML(), after);
     });
   }
@@ -117,6 +120,13 @@ asyncSuite('each_new', [
   ['two', { x: Promise.resolve([1, 2]) }, '0', '12'],
 ]);
 
+asyncSuite('with', [
+  ['null', { x: Promise.resolve(null) }, '', '', 2],
+  ['empty', { x: Promise.resolve({}) }, '', '', 2],
+  ['direct', { x: Promise.resolve({y: 1}) }, '', '1', 2],
+  ['wrapped', { x: Promise.resolve({y: Promise.resolve(1)}) }, '', '1', 3],
+]);
+
 // In the following tests pending=1, rejected=2, resolved=3.
 const pending = new Promise(() => {});
 const rejected = Promise.reject();

packages/templating-runtime/templating.js

@@ -138,7 +138,7 @@ Template._applyHmrChanges = function (templateName) {
           var newView = Blaze.render(Template.body, document.body, comment);
           Template.body.view = newView;
         } else if (view.dataVar) {
-          Blaze.renderWithData(renderFunc, view.dataVar.curValue, parentEl, comment);
+          Blaze.renderWithData(renderFunc, view.dataVar.curValue?.value, parentEl, comment);
         } else {
           Blaze.render(renderFunc, parentEl, comment);
         }