add test for the issue

spacy/tests/regression/test_issue1834.py

@@ -0,0 +1,27 @@
+from __future__ import unicode_literals
+from ...tokens import Doc
+from ...vocab import Vocab
+
+
+def test_issue1834():
+    """test if sentence boundaries & parse/tag flags are not lost
+    during serialization
+    """
+    words = "This is a first sentence . And another one".split()
+    vocab = Vocab()
+    doc = Doc(vocab, words=words)
+    vocab = doc.vocab
+    doc[6].sent_start = True
+    deser_doc = Doc(vocab).from_bytes(doc.to_bytes())
+    assert deser_doc[6].sent_start
+    assert not deser_doc.is_parsed
+    assert not deser_doc.is_tagged
+    doc.is_parsed = True
+    doc.is_tagged = True
+    deser_doc = Doc(vocab).from_bytes(doc.to_bytes())
+    assert deser_doc.is_parsed
+    assert deser_doc.is_tagged
+
+
+
+