improve formatting template code

* do not intend empty lines
* strip leading and trailing newlines

Author: jelhan

lib/__tests__/__snapshots__/transform.js.snap

@@ -23,6 +23,28 @@ foo
 =========="
 `;
 
+exports[`classic components empty lines are not intended 1`] = `
+"==========
+export default Component.extend({});
+~~~~~~~~~~
+foo
+
+bar
+~~~~~~~~~~
+ => tagName: div
+~~~~~~~~~~
+export default Component.extend({
+  tagName: \\"\\"
+});
+~~~~~~~~~~
+<div ...attributes>
+  foo
+
+  bar
+</div>
+=========="
+`;
+
 exports[`classic components handles \`ariaRole\` correctly 1`] = `
 "==========
 
@@ -191,6 +213,26 @@ foo
 =========="
 `;
 
+exports[`classic components leading and trailing empty lines are stripped 1`] = `
+"==========
+export default Component.extend({});
+~~~~~~~~~~
+
+foo
+
+~~~~~~~~~~
+ => tagName: div
+~~~~~~~~~~
+export default Component.extend({
+  tagName: \\"\\"
+});
+~~~~~~~~~~
+<div ...attributes>
+  foo
+</div>
+=========="
+`;
+
 exports[`classic components multi-line template 1`] = `
 "==========
 export default Component.extend({});
@@ -511,7 +553,7 @@ foo
       }
     
 ~~~~~~~~~~
-<div class=\\"{{styleNamespace}} foo bar:baz\\" ...attributes>
+<div class=\\"{{this.styleNamespace}} foo bar:baz\\" ...attributes>
   foo
 </div>
 =========="

lib/__tests__/transform.js

@@ -231,6 +231,26 @@ describe('classic components', function() {
     expect(generateSnapshot(source, template)).toMatchSnapshot();
   });
 
+  test('empty lines are not intended', () => {
+    let source = `export default Component.extend({});`;
+
+    let template = `foo
+
+bar`;
+
+    expect(generateSnapshot(source, template)).toMatchSnapshot();
+  });
+
+  test('leading and trailing empty lines are stripped', () => {
+    let source = `export default Component.extend({});`;
+
+    let template = `
+foo
+`;
+
+    expect(generateSnapshot(source, template)).toMatchSnapshot();
+  });
+
   test('handles `hasComponentCSS` option correctly', () => {
     let source = `
     export default Component.extend({

lib/utils/template.js

@@ -1,8 +1,15 @@
 function indentLines(content) {
-  return content
-    .split('\n')
-    .map(it => `  ${it}`)
-    .join('\n');
+  return (
+    content
+      // strip leading and trailing new lines
+      .trim()
+      .split('\n')
+      .map(it => {
+        // intend non-empty lines with two spaces
+        return it.trim().length > 0 ? `  ${it}` : '';
+      })
+      .join('\n')
+  );
 }
 
 module.exports = {