Added LineBreakHandler to resolve missing line breaks

CONTRIBUTORS.rst

@@ -276,6 +276,7 @@ Contributors
 * Ben Weatherman
 * Carlo Ascani
 * Julian Gallo
+* Dan Dietz
 
 Translators
 ===========

wagtail/admin/rich_text/converters/html_to_contentstate.py

@@ -215,11 +215,24 @@ class HorizontalRuleHandler(AtomicBlockEntityElementHandler):
         return Entity('HORIZONTAL_RULE', 'IMMUTABLE', {})
 
 
+class LineBreakHandler:
+    def handle_starttag(self, name, attrs, state, contentstate):
+        if state.current_block is None:
+            # ignore line breaks that exist at the top level
+            return
+
+        state.current_block.text += '\n'
+
+    def handle_endtag(self, name, state, contentstate):
+        pass
+
+
 class HtmlToContentStateHandler(HTMLParser):
     def __init__(self, features=()):
         self.paragraph_handler = BlockElementHandler('unstyled')
         self.element_handlers = HTMLRuleset({
-            'p': self.paragraph_handler
+            'p': self.paragraph_handler,
+            'br': LineBreakHandler(),
         })
         for feature in features:
             rule = feature_registry.get_converter_rule('contentstate', feature)

wagtail/admin/tests/test_contentstate.py

@@ -436,6 +436,38 @@ class TestHtmlToContentState(TestCase):
             }
         })
 
+    def test_br_element_in_paragraph(self):
+        converter = ContentstateConverter(features=[])
+        result = json.loads(converter.from_database_format(
+            '''
+            <p>before<br/>after</p>
+            '''
+        ))
+        self.assertContentStateEqual(result, {
+            'entityMap': {},
+            'blocks': [
+                {'key': '00000', 'inlineStyleRanges': [], 'entityRanges': [], 'depth': 0, 'text': 'before\nafter',
+                 'type': 'unstyled'}
+            ],
+        })
+
+    def test_br_element_between_paragraphs(self):
+        converter = ContentstateConverter(features=[])
+        result = json.loads(converter.from_database_format(
+            '''
+            <p>before</p>
+            <br />
+            <p>after</p>
+            '''
+        ))
+        self.assertContentStateEqual(result, {
+            'entityMap': {},
+            'blocks': [
+                {'key': '00000', 'inlineStyleRanges': [], 'entityRanges': [], 'depth': 0, 'text': 'before', 'type': 'unstyled'},
+                {'key': '00000', 'inlineStyleRanges': [], 'entityRanges': [], 'depth': 0, 'text': 'after', 'type': 'unstyled'}
+            ],
+        })
+
     def test_block_element_in_empty_paragraph(self):
         converter = ContentstateConverter(features=['hr'])
         result = json.loads(converter.from_database_format(