Fix non-empty blank lines in indented code

Author: wooorm

lib/util/indent-lines.js

@@ -1,6 +1,5 @@
 module.exports = indentLines
 
-var blank = /^[\t ]*$/
 var eol = /\r?\n|\r/g
 
 function indentLines(value, map) {
@@ -21,6 +20,6 @@ function indentLines(value, map) {
   return result.join('')
 
   function one(value) {
-    result.push(map(value, line, blank.test(value)))
+    result.push(map(value, line, !value))
   }
 }

test.js

@@ -2522,5 +2522,22 @@ test('roundtrip', function (t) {
 
   t.equal(to(from(doc)), doc, 'should roundtrip lists with break comments')
 
+  // The first one could have (up to) four spaces, but it doesn’t add anything,
+  // so we don’t roundtrip it.
+  doc = [
+    '    <h3>Header 3</h3>',
+    '',
+    '    <blockquote>',
+    '        <p>This is a blockquote.</p>',
+    '        ',
+    '        <p>This is the second paragraph in the blockquote.</p>',
+    '        ',
+    '        <h2>This is an H2 in a blockquote</h2>',
+    '    </blockquote>',
+    ''
+  ].join('\n')
+
+  t.equal(to(from(doc)), doc, 'should roundtrip indented blank lines in code')
+
   t.end()
 })