hdr: add DocumentPart.add_header_part()

Author: ondrej-111

docx/parts/document.py

@@ -8,6 +8,7 @@
 from docx.opc.constants import RELATIONSHIP_TYPE as RT
 from docx.opc.part import XmlPart
 from docx.oxml.shape import CT_Inline
+from docx.parts.hdrftr import HeaderPart
 from docx.parts.numbering import NumberingPart
 from docx.parts.settings import SettingsPart
 from docx.parts.styles import StylesPart
@@ -26,7 +27,9 @@ class DocumentPart(XmlPart):
 
     def add_header_part(self):
         """Return (header_part, rId) pair for newly-created header part."""
-        raise NotImplementedError
+        header_part = HeaderPart.new(self.package)
+        rId = self.relate_to(header_part, RT.HEADER)
+        return header_part, rId
 
     @property
     def core_properties(self):

docx/parts/hdrftr.py

@@ -9,3 +9,8 @@
 
 class HeaderPart(XmlPart):
     """Definition of a section header."""
+
+    @classmethod
+    def new(cls, package):
+        """Return newly created header part."""
+        raise NotImplementedError

tests/parts/test_document.py

@@ -11,6 +11,7 @@
 from docx.opc.coreprops import CoreProperties
 from docx.package import Package
 from docx.parts.document import DocumentPart
+from docx.parts.hdrftr import HeaderPart
 from docx.parts.image import ImagePart
 from docx.parts.numbering import NumberingPart
 from docx.parts.settings import SettingsPart
@@ -30,6 +31,18 @@
 
 class DescribeDocumentPart(object):
 
+    def it_can_add_a_header_part(self, package_, HeaderPart_, header_part_, relate_to_):
+        HeaderPart_.new.return_value = header_part_
+        relate_to_.return_value = "rId7"
+        document_part = DocumentPart(None, None, None, package_)
+
+        header_part, rId = document_part.add_header_part()
+
+        HeaderPart_.new.assert_called_once_with(package_)
+        relate_to_.assert_called_once_with(document_part, header_part_, RT.HEADER)
+        assert header_part is header_part_
+        assert rId == "rId7"
+
     def it_can_drop_a_specified_header_part(self, drop_rel_):
         document_part = DocumentPart(None, None, None, None)
 
@@ -277,6 +290,14 @@ def drop_rel_(self, request):
     def get_or_add_image_(self, request):
         return method_mock(request, DocumentPart, 'get_or_add_image')
 
+    @pytest.fixture
+    def HeaderPart_(self, request):
+        return class_mock(request, 'docx.parts.document.HeaderPart')
+
+    @pytest.fixture
+    def header_part_(self, request):
+        return instance_mock(request, HeaderPart)
+
     @pytest.fixture
     def image_(self, request):
         return instance_mock(request, Image)