Skip tagName='' tagless components

Fixes #64

Author: simonihmig

lib/__tests__/transform.js

@@ -488,7 +488,7 @@ describe('native components', function() {
     expect(generateSnapshot(source, template)).toMatchSnapshot();
   });
 
-  test('skips tagless components', () => {
+  test("skips @tagName('') components", () => {
     let source = `
       import Component from '@ember/component';
       import { tagName } from '@ember-decorators/component';
@@ -506,6 +506,23 @@ describe('native components', function() {
     expect(result.template).toEqual(template);
   });
 
+  test("skips tagName='' components", () => {
+    let source = `
+      import Component from '@ember/component';
+
+      export default class FooComponent extends Component {
+        tagName = '';
+      }
+    `;
+
+    let template = 'foo';
+
+    let result = transform(source, template);
+    expect(result.tagName).toEqual(undefined);
+    expect(result.source).toEqual(source);
+    expect(result.template).toEqual(template);
+  });
+
   test('throws if component is using `this.element`', () => {
     let source = `
       import Component from '@ember/component';

lib/utils/native.js

@@ -77,9 +77,12 @@ function findStringDecorator(path, name) {
   return decorator.value.expression.arguments[0].value;
 }
 
-function findTagName(path) {
-  let value = findStringDecorator(path, 'tagName');
-  return value !== undefined ? value : 'div';
+function findTagName(classDeclaration) {
+  let value = findStringDecorator(classDeclaration, 'tagName');
+  if (value === undefined) {
+    value = findStringProperty(classDeclaration.get('body', 'body'), 'tagName');
+  }
+  return value !== undefined && value !== null ? value : 'div';
 }
 
 function findElementId(path) {