Fix to not add multiple line feeds at end of file

Closes GH-440.

Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Co-authored-by: Evandro Oliveira <evandrofranco@gmail.com>
Co-authored-by: Titus Wormer <tituswormer@gmail.com>

packages/remark-stringify/lib/visitors/root.js

@@ -7,5 +7,11 @@ var lineFeed = '\n'
 // Stringify a root.
 // Adds a final newline to ensure valid POSIX files. */
 function root(node) {
-  return this.block(node) + lineFeed
+  var doc = this.block(node)
+
+  if (doc.charAt(doc.length - 1) !== lineFeed) {
+    doc += lineFeed
+  }
+
+  return doc
 }

packages/remark-stringify/test.js

@@ -18,6 +18,18 @@ var pedantic = {pedantic: true}
 var uncollapsable = {start: {line: 1, column: NaN}, end: {line: 1, column: NaN}}
 
 test('remark().stringify(ast, file)', function(t) {
+  t.equal(
+    unified()
+      .use(stringify)
+      .stringify({
+        type: 'root',
+        children: [{type: 'html', value: '<!-- last line\n'}]
+      })
+      .toString(),
+    '<!-- last line\n',
+    'should not add more than one line feeds at the end'
+  )
+
   t.throws(
     function() {
       unified()