[BUGFIX] Fix contextual components handling invalid component paths

packages/ember-htmlbars/lib/keywords/closure-component.js

@@ -3,6 +3,8 @@
 @submodule ember-templates
 */
 
+import { assert } from 'ember-metal/debug';
+import isNone from 'ember-metal/is_none';
 import { symbol } from 'ember-metal/utils';
 import BasicStream from 'ember-metal/streams/stream';
 import { read } from 'ember-metal/streams/utils';
@@ -27,7 +29,7 @@ let ClosureComponentStream = BasicStream.extend({
     this[COMPONENT_REFERENCE] = true;
   },
   compute() {
-    return createClosureComponentCell(this._env, this._path, this._params, this._hash);
+    return createClosureComponentCell(this._env, this._path, this._params, this._hash, this.label);
   }
 });
 
@@ -46,16 +48,27 @@ export default function closureComponent(env, [path, ...params], hash) {
   return s;
 }
 
-function createClosureComponentCell(env, originalComponentPath, params, hash) {
+function createClosureComponentCell(env, originalComponentPath, params, hash, label) {
   let componentPath = read(originalComponentPath);
 
+  assert(`Component path cannot be null in ${label}`,
+         !isNone(componentPath));
+
   if (isComponentCell(componentPath)) {
     return createNestedClosureComponentCell(componentPath, params, hash);
   } else {
+    assert(`The component helper cannot be used without a valid component name. You used "${componentPath}" via ${label}`,
+          isValidComponentPath(env, componentPath));
     return createNewClosureComponentCell(env, componentPath, params, hash);
   }
 }
 
+function isValidComponentPath(env, path) {
+  const result = lookupComponent(env.container, path);
+
+  return !!(result.component || result.layout);
+}
+
 export function isComponentCell(component) {
   return component && component[COMPONENT_CELL];
 }

packages/ember-htmlbars/tests/helpers/closure_component_test.js

@@ -101,13 +101,14 @@ if (isEnabled('ember-contextual-components')) {
     );
 
     let template = compile('{{component (component lookupComponent)}}');
-    component = Component.extend({ container, template }).create();
+    component = Component.extend({
+      container,
+      template,
+      lookupComponent: '-mandarin'
+    }).create();
 
     runAppend(component);
-    equal(component.$().text(), ``, 'undefined lookupComponent does not render');
-    run(() => {
-      component.set('lookupComponent', '-mandarin');
-    });
+
     equal(component.$().text(), `ni hao`,
           'mandarin lookupComponent renders greeting');
     run(() => {
@@ -309,4 +310,33 @@ if (isEnabled('ember-contextual-components')) {
     runAppend(component);
     equal(component.$().text(), 'Hodi Sergio', 'component is rendered');
   });
+
+  QUnit.test('raises an assertion when component path is null', function() {
+    let template = compile(`{{component (component lookupComponent)}}`);
+    component = Component.extend({ container, template }).create();
+
+    expectAssertion(() => {
+      runAppend(component);
+    });
+  });
+
+  QUnit.test('raises an assertion when component path is not a component name', function() {
+    let template = compile(`{{component (component "not-a-component")}}`);
+    component = Component.extend({ container, template }).create();
+
+    expectAssertion(() => {
+      runAppend(component);
+    }, `The component helper cannot be used without a valid component name. You used "not-a-component" via (component "not-a-component")`);
+
+    template = compile(`{{component (component compName)}}`);
+    component = Component.extend({
+      container,
+      template,
+      compName: 'not-a-component'
+    }).create();
+
+    expectAssertion(() => {
+      runAppend(component);
+    }, `The component helper cannot be used without a valid component name. You used "not-a-component" via (component compName)`);
+  });
 }