pkg: add OpcPackage.next_partname()

Author: scanny

docx/opc/package.py

@@ -1,27 +1,24 @@
 # encoding: utf-8
 
-"""
-The :mod:`pptx.packaging` module coheres around the concerns of reading and
-writing presentations to and from a .pptx file.
-"""
+"""Objects that implement reading and writing OPC packages."""
 
-from __future__ import absolute_import, print_function, unicode_literals
+from __future__ import absolute_import, division, print_function, unicode_literals
 
-from .constants import RELATIONSHIP_TYPE as RT
-from .packuri import PACKAGE_URI
-from .part import PartFactory
-from .parts.coreprops import CorePropertiesPart
-from .pkgreader import PackageReader
-from .pkgwriter import PackageWriter
-from .rel import Relationships
-from .shared import lazyproperty
+from docx.opc.constants import RELATIONSHIP_TYPE as RT
+from docx.opc.packuri import PACKAGE_URI, PackURI
+from docx.opc.part import PartFactory
+from docx.opc.parts.coreprops import CorePropertiesPart
+from docx.opc.pkgreader import PackageReader
+from docx.opc.pkgwriter import PackageWriter
+from docx.opc.rel import Relationships
+from docx.opc.shared import lazyproperty
 
 
 class OpcPackage(object):
-    """
-    Main API class for |python-opc|. A new instance is constructed by calling
-    the :meth:`open` class method with a path to a package file or file-like
-    object containing one.
+    """Main API class for |python-opc|.
+
+    A new instance is constructed by calling the :meth:`open` class method with a path
+    to a package file or file-like object containing one.
     """
 
     def __init__(self):
@@ -116,7 +113,11 @@ def next_partname(self, template):
         containing a single replacement item, a '%d' to be used to insert the integer
         portion of the partname. Example: "/word/header%d.xml"
         """
-        raise NotImplementedError
+        partnames = {part.partname for part in self.iter_parts()}
+        for n in range(1, len(partnames) + 2):
+            candidate_partname = template % n
+            if candidate_partname not in partnames:
+                return PackURI(candidate_partname)
 
     @classmethod
     def open(cls, pkg_file):

tests/opc/test_package.py

@@ -9,7 +9,7 @@
 from docx.opc.constants import RELATIONSHIP_TYPE as RT
 from docx.opc.coreprops import CoreProperties
 from docx.opc.package import OpcPackage, Unmarshaller
-from docx.opc.packuri import PACKAGE_URI
+from docx.opc.packuri import PACKAGE_URI, PackURI
 from docx.opc.part import Part
 from docx.opc.parts.coreprops import CorePropertiesPart
 from docx.opc.pkgreader import PackageReader
@@ -101,6 +101,20 @@ def it_can_iterate_over_parts_by_walking_rels_graph(self):
         assert part2 in pkg.iter_parts()
         assert len([p for p in pkg.iter_parts()]) == 2
 
+    def it_can_find_the_next_available_vector_partname(
+        self, next_partname_fixture, iter_parts_, PackURI_, packuri_
+    ):
+        """A vector partname is one with a numeric suffix, like header42.xml."""
+        parts_, expected_value = next_partname_fixture
+        iter_parts_.return_value = iter(parts_)
+        PackURI_.return_value = packuri_
+        package = OpcPackage()
+
+        partname = package.next_partname(template="/foo/bar/baz%d.xml")
+
+        PackURI_.assert_called_once_with(expected_value)
+        assert partname is packuri_
+
     def it_can_find_a_part_related_by_reltype(self, related_part_fixture_):
         pkg, reltype, related_part_ = related_part_fixture_
         related_part = pkg.part_related_by(reltype)
@@ -161,6 +175,20 @@ def core_props_part_fixture(
         part_related_by_.return_value = core_properties_part_
         return opc_package, core_properties_part_
 
+    @pytest.fixture(
+        params=[((), 1), ((1,), 2), ((1, 2), 3), ((2, 3), 1), ((1, 3), 2)]
+    )
+    def next_partname_fixture(self, request, iter_parts_):
+        existing_partname_ns, next_partname_n = request.param
+        parts_ = [
+            instance_mock(
+                request, Part, name="part[%d]" % idx, partname="/foo/bar/baz%d.xml" % n
+            )
+            for idx, n in enumerate(existing_partname_ns)
+        ]
+        expected_value = "/foo/bar/baz%d.xml" % next_partname_n
+        return parts_, expected_value
+
     @pytest.fixture
     def relate_to_part_fixture_(self, request, pkg, rels_, reltype):
         rId = 'rId99'
@@ -196,10 +224,22 @@ def core_properties_part_(self, request):
     def _core_properties_part_prop_(self, request):
         return property_mock(request, OpcPackage, '_core_properties_part')
 
+    @pytest.fixture
+    def iter_parts_(self, request):
+        return method_mock(request, OpcPackage, "iter_parts")
+
     @pytest.fixture
     def PackageReader_(self, request):
         return class_mock(request, 'docx.opc.package.PackageReader')
 
+    @pytest.fixture
+    def PackURI_(self, request):
+        return class_mock(request, "docx.opc.package.PackURI")
+
+    @pytest.fixture
+    def packuri_(self, request):
+        return instance_mock(request, PackURI)
+
     @pytest.fixture
     def PackageWriter_(self, request):
         return class_mock(request, 'docx.opc.package.PackageWriter')