Ensure path in Doc.to_disk/from_disk (resolves ##1521)

Also add Doc serialization tests with both Path and string path options

spacy/tests/serialize/test_serialize_doc.py

@@ -0,0 +1,34 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+from ..util import make_tempdir, get_doc
+from ...tokens import Doc
+from ...compat import path2str
+
+import pytest
+
+
+def test_serialize_doc_roundtrip_bytes(en_vocab):
+    doc = get_doc(en_vocab, words=['hello', 'world'])
+    doc_b = doc.to_bytes()
+    new_doc = Doc(en_vocab).from_bytes(doc_b)
+    assert new_doc.to_bytes() == doc_b
+
+
+def test_serialize_doc_roundtrip_disk(en_vocab):
+    doc = get_doc(en_vocab, words=['hello', 'world'])
+    with make_tempdir() as d:
+        file_path = d / 'doc'
+        doc.to_disk(file_path)
+        doc_d = Doc(en_vocab).from_disk(file_path)
+        assert doc.to_bytes() == doc_d.to_bytes()
+
+
+def test_serialize_doc_roundtrip_disk_str_path(en_vocab):
+    doc = get_doc(en_vocab, words=['hello', 'world'])
+    with make_tempdir() as d:
+        file_path = d / 'doc'
+        file_path = path2str(file_path)
+        doc.to_disk(file_path)
+        doc_d = Doc(en_vocab).from_disk(file_path)
+        assert doc.to_bytes() == doc_d.to_bytes()

spacy/tokens/doc.pyx

@@ -737,6 +737,7 @@ cdef class Doc:
         path (unicode or Path): A path to a directory, which will be created if
             it doesn't exist. Paths may be either strings or Path-like objects.
         """
+        path = util.ensure_path(path)
         with path.open('wb') as file_:
             file_.write(self.to_bytes(**exclude))
 
@@ -748,6 +749,7 @@ cdef class Doc:
             strings or `Path`-like objects.
         RETURNS (Doc): The modified `Doc` object.
         """
+        path = util.ensure_path(path)
         with path.open('rb') as file_:
             bytes_data = file_.read()
         return self.from_bytes(bytes_data, **exclude)