fix: preserve text nested inside <br> by html.parser

Python's html.parser can wrap text following <br /> (with a space) inside
the <br> element as child content when the <br> is preceded by a sibling
<br> without a slash.  convert_br received the nested text via its `text`
parameter but discarded it, silently dropping characters from the output.

Append `text` to the returned line-break marker so that any accidentally
nested content is always preserved.

Closes #244

Author: binggao1230

markdownify/__init__.py

@@ -475,12 +475,12 @@ def _indent_for_blockquote(match):
 
     def convert_br(self, el, text, parent_tags):
         if '_inline' in parent_tags:
-            return ' '
+            return text + ' ' if text else ' '
 
         if self.options['newline_style'].lower() == BACKSLASH:
-            return '\\\n'
+            return '\\\n' + text
         else:
-            return '  \n'
+            return '  \n' + text
 
     def convert_code(self, el, text, parent_tags):
         if '_noformat' in parent_tags:

tests/test_conversions.py

@@ -81,6 +81,9 @@ def test_br():
     assert md('a<br />b<br />c', newline_style=BACKSLASH) == 'a\\\nb\\\nc'
     assert md('<h1>foo<br />bar</h1>', heading_style=ATX) == '\n\n# foo bar\n\n'
     assert md('<td>foo<br />bar</td>', heading_style=ATX) == ' foo bar |'
+    # html.parser may nest text inside <br> when mixing <br> and <br />; text must not be lost
+    assert md('a<br>b<br />c') == 'a  \nb  \nc'
+    assert md('a<br>b<br />c', newline_style=BACKSLASH) == 'a\\\nb\\\nc'
 
 
 def test_code():