doc: add _Document.next_id

Steve Canny · Steve Canny · commit 422c504ad621 · 2013-12-27T03:24:17.000-08:00
diff --git a/docx/parts/document.py b/docx/parts/document.py
@@ -69,7 +69,11 @@ def next_id(self):
         in id sequence are filled. The id attribute value is unique in the
         document, without regard to the element type it appears on.
         """
-        raise NotImplementedError
+        id_str_lst = self._element.xpath('//@id')
+        used_ids = [int(id_str) for id_str in id_str_lst]
+        for n in range(1, len(used_ids)+2):
+            if n not in used_ids:
+                return n
 
     @property
     def part(self):
diff --git a/tests/parts/test_document.py b/tests/parts/test_document.py
@@ -89,6 +89,10 @@ def it_provides_access_to_the_inline_shapes_in_the_document(
     def it_knows_it_is_the_part_its_child_objects_belong_to(self, document):
         assert document.part is document
 
+    def it_knows_the_next_available_xml_id(self, next_id_fixture):
+        document, expected_id = next_id_fixture
+        assert document.next_id == expected_id
+
     # fixtures -------------------------------------------------------
 
     @pytest.fixture
@@ -157,6 +161,20 @@ def inline_shapes_fixture(self, request, InlineShapes_):
         document = _Document(None, None, document_elm, None)
         return document, InlineShapes_, body_elm
 
+    @pytest.fixture(params=[
+        ((), 1), ((1,), 2), ((2,), 1), ((1, 2, 3), 4), ((1, 2, 4), 3),
+        ((0, 0), 1), ((0, 0, 1, 3), 2),
+    ])
+    def next_id_fixture(self, request):
+        existing_ids, expected_id = request.param
+        document_elm = a_document().with_nsdecls().element
+        for n in existing_ids:
+            p = a_p().with_nsdecls().element
+            p.set('id', str(n))
+            document_elm.append(p)
+        document = _Document(None, None, document_elm, None)
+        return document, expected_id
+
     @pytest.fixture
     def oxml_fromstring_(self, request):
         return function_mock(request, 'docx.parts.document.oxml_fromstring')
