Fix html (text) from being seen as html (flow)

Closes GH-15.

Author: wooorm

lib/handle/html.js

@@ -1,5 +1,10 @@
 module.exports = html
+html.peek = htmlPeek
 
 function html(node) {
   return node.value || ''
 }
+
+function htmlPeek() {
+  return '<'
+}

lib/util/container-phrasing.js

@@ -25,12 +25,27 @@ function phrasing(parent, context, safeOptions) {
       after = safeOptions.after
     }
 
+    // In some cases, html (text) can be found in phrasing right after an eol.
+    // When we’d serialize that, in most cases that would be seen as html
+    // (flow).
+    // As we can’t escape or so to prevent it from happening, we take a somewhat
+    // reasonable approach: replace that eol with a space.
+    // See: <https://github.com/syntax-tree/mdast-util-to-markdown/issues/15>
+    if ((before === '\r' || before === '\n') && child.type === 'html') {
+      results[results.length - 1] = results[results.length - 1].replace(
+        /(\r?\n|\r)$/,
+        ' '
+      )
+      before = ' '
+    }
+
     results.push(
       context.handle(child, parent, context, {
         before: before,
         after: after
       })
     )
+
     before = results[results.length - 1].slice(-1)
   }
 

test.js

@@ -1067,6 +1067,43 @@ test('html', function (t) {
   t.equal(to({type: 'html'}), '', 'should support a void html')
   t.equal(to({type: 'html', value: ''}), '', 'should support an empty html')
   t.equal(to({type: 'html', value: 'a\nb'}), 'a\nb\n', 'should support html')
+
+  t.equal(
+    to({
+      type: 'paragraph',
+      children: [
+        {type: 'text', value: 'a\n'},
+        {type: 'html', value: '<div>'}
+      ]
+    }),
+    'a <div>\n',
+    'should prevent html (text) from becoming html (flow) (1)'
+  )
+
+  t.equal(
+    to({
+      type: 'paragraph',
+      children: [
+        {type: 'text', value: 'a\r'},
+        {type: 'html', value: '<div>'}
+      ]
+    }),
+    'a <div>\n',
+    'should prevent html (text) from becoming html (flow) (2)'
+  )
+
+  t.equal(
+    to({
+      type: 'paragraph',
+      children: [
+        {type: 'text', value: 'a\r\n'},
+        {type: 'html', value: '<div>'}
+      ]
+    }),
+    'a <div>\n',
+    'should prevent html (text) from becoming html (flow) (3)'
+  )
+
   t.end()
 })