Conservative backport of #852 to release-0-25

Author: chancancode

packages/@glimmer/runtime/lib/dom/helper.ts

@@ -193,7 +193,7 @@ export class DOMChanges extends DOMOperations {
   }
 }
 
-export function insertHTMLBefore(this: void, _useless: Simple.Element, _parent: Simple.Element, _nextSibling: Option<Simple.Node>, html: string): Bounds { // tslint:disable-line
+export function insertHTMLBefore(this: void, _useless: Simple.Element, _parent: Simple.Element, _nextSibling: Option<Simple.Node>, _html: string): Bounds { // tslint:disable-line
   // TypeScript vendored an old version of the DOM spec where `insertAdjacentHTML`
   // only exists on `HTMLElement` but not on `Element`. We actually work with the
   // newer version of the DOM API here (and monkey-patch this method in `./compat`
@@ -205,9 +205,7 @@ export function insertHTMLBefore(this: void, _useless: Simple.Element, _parent:
   let prev = nextSibling ? nextSibling.previousSibling : parent.lastChild;
   let last: Simple.Node | null;
 
-  if (html === null || html === '') {
-    return new ConcreteBounds(parent, null, null);
-  }
+  let html = _html || '<!---->';
 
   if (nextSibling === null) {
     parent.insertAdjacentHTML('beforeend', html);

packages/@glimmer/runtime/test/updating-test.ts

@@ -619,59 +619,67 @@ module("[glimmer-runtime] Updating", hooks => {
     }]
   }, {
     name: 'triple curlies',
-    template: '<div>{{{value}}}</div>',
+    template: '<div>before {{{value}}} after</div>',
     values: [{
       input: 'hello',
-      expected: '<div>hello</div>',
+      expected: '<div>before hello after</div>',
       description: 'plain string'
     }, {
       input: '<b>hello</b>',
-      expected: '<div><b>hello</b></div>',
+      expected: '<div>before <b>hello</b> after</div>',
       description: 'string containing HTML'
     }, {
       input: null,
-      expected: '<div></div>',
+      expected: '<div>before <!---> after</div>',
       description: 'null literal'
     }, {
       input: undefined,
-      expected: '<div></div>',
+      expected: '<div>before <!---> after</div>',
       description: 'undefined literal'
     }, {
+      input: ' ',
+      expected: '<div>before   after</div>',
+      description: 'blank string',
+    },{
       input: makeSafeString('<b>hello</b>'),
-      expected: '<div><b>hello</b></div>',
+      expected: '<div>before <b>hello</b> after</div>',
       description: 'safe string containing HTML'
     }, {
       input: makeElement('p', 'hello'),
-      expected: '<div><p>hello</p></div>',
+      expected: '<div>before <p>hello</p> after</div>',
       description: 'DOM node containing and element with text'
     }, {
       input: makeFragment([makeElement('p', 'one'), makeElement('p', 'two')]),
-      expected: '<div><p>one</p><p>two</p></div>',
+      expected: '<div>before <p>one</p><p>two</p> after</div>',
       description: 'DOM fragment containing multiple nodes'
     }, {
       input: 'not modified',
-      expected: '<div>not modified</div>',
+      expected: '<div>before not modified after</div>',
       description: 'plain string (not modified, first render)'
     }, {
       input: 'not modified',
-      expected: '<div>not modified</div>',
+      expected: '<div>before not modified after</div>',
       description: 'plain string (not modified, second render)'
     }, {
       input: 0,
-      expected: '<div>0</div>',
+      expected: '<div>before 0 after</div>',
       description: 'number literal (0)'
     }, {
       input: true,
-      expected: '<div>true</div>',
+      expected: '<div>before true after</div>',
       description: 'boolean literal (true)'
     }, {
       input: {
         toString() {
           return 'I am an Object';
         }
       },
-      expected: '<div>I am an Object</div>',
+      expected: '<div>before I am an Object after</div>',
       description: 'object with a toString function'
+    }, {
+      input: 'hello',
+      expected: '<div>before hello after</div>',
+      description: 'reset',
     }]
   }].forEach(config => {
     test(`updating ${config.name} produces expected result`, () => {
@@ -737,11 +745,11 @@ module("[glimmer-runtime] Updating", hooks => {
 
     render(template, input);
 
-    equalTokens(root, '<div></div>', "Initial render");
+    equalTokens(root, '<div><!----></div>', "Initial render");
 
     rerender();
 
-    equalTokens(root, '<div></div>', "no change");
+    equalTokens(root, '<div><!----></div>', "no change");
 
     input.value = '<b>Bold and spicy</b>';
     rerender();
@@ -751,7 +759,7 @@ module("[glimmer-runtime] Updating", hooks => {
     input.value = '';
     rerender();
 
-    equalTokens(root, '<div></div>', "back to empty string");
+    equalTokens(root, '<div><!----></div>', "back to empty string");
   });
 
   class ValueReference<T> extends ConstReference<T> {