Liblink: Add test over direct vs indirect link status.

Some checks are currently commented out, since Blender will never 'clear'
the directly linked status of an ID once it has been used by local data.

tests/python/bl_blendfile_liblink.py

@@ -188,6 +188,90 @@ class TestBlendLibLinkSaveLoadBasic(TestBlendLibLinkHelper):
         assert orig_data == read_data
 
 
+class TestBlendLibLinkIndirect(TestBlendLibLinkHelper):
+
+    def __init__(self, args):
+        self.args = args
+
+    def test_append(self):
+        output_dir = self.args.output_dir
+        output_lib_path = self.init_lib_data_indirect_lib()
+
+        # Simple link of a single ObData.
+        self.reset_blender()
+
+        link_dir = os.path.join(output_lib_path, "Mesh")
+        bpy.ops.wm.link(directory=link_dir, filename="LibMesh", instance_object_data=False)
+
+        assert len(bpy.data.materials) == 1
+        assert len(bpy.data.meshes) == 1
+        assert len(bpy.data.objects) == 0
+        assert len(bpy.data.collections) == 0  # Scene's master collection is not listed here
+
+        mesh = bpy.data.meshes[0]
+        material = bpy.data.materials[0]
+
+        assert material.library is not None
+        assert material.use_fake_user is True
+        assert material.users == 2  # Fake user is not cleared when linking.
+        assert material.is_library_indirect == True
+
+        assert mesh.library is not None
+        assert mesh.use_fake_user is False
+        assert mesh.users == 0
+        assert mesh.is_library_indirect == False  # IDs explicitely linked by the user are forcefully considered directly linked.
+
+        ob = bpy.data.objects.new("LocalMesh", mesh)
+        coll = bpy.data.collections.new("LocalMesh")
+        coll.objects.link(ob)
+        bpy.context.scene.collection.children.link(coll)
+
+        assert material.users == 2
+        assert material.is_library_indirect == True
+        assert mesh.users == 1
+        assert mesh.is_library_indirect == False
+
+        ob.material_slots[0].link = 'OBJECT'
+        ob.material_slots[0].material = material
+
+        assert material.users == 3
+        assert material.is_library_indirect == False
+
+        ob.material_slots[0].material = None
+
+        assert material.users == 2
+        assert material.is_library_indirect == False  # This is not properly updated whene removing a local user of linked data.
+
+        output_work_path = os.path.join(output_dir, self.unique_blendfile_name("blendfile"))
+        bpy.ops.wm.save_as_mainfile(filepath=output_work_path, check_existing=False, compress=False)
+
+        assert material.users == 2
+        # Currently linked data which has no more local user never gets reset to indirectly linked status.
+        # ~ assert material.is_library_indirect == True
+
+        bpy.ops.wm.open_mainfile(filepath=output_work_path, load_ui=False)
+
+        assert len(bpy.data.materials) == 1
+        assert len(bpy.data.meshes) == 1
+        assert len(bpy.data.objects) == 1
+        assert len(bpy.data.collections) == 1  # Scene's master collection is not listed here
+
+        mesh = bpy.data.meshes[0]
+        material = bpy.data.materials[0]
+
+        assert material.library is not None
+        assert material.use_fake_user is True
+        assert material.users == 2  # Fake user is not cleared when linking.
+        # Currently even re-reading the .blend file will not properly reset tag for indirectly linked data,
+        # if their reference was written in the .blend file.
+        # ~ assert material.is_library_indirect == True
+
+        assert mesh.library is not None
+        assert mesh.use_fake_user is False
+        assert mesh.users == 1
+        assert mesh.is_library_indirect == False
+
+
 class TestBlendLibAppendBasic(TestBlendLibLinkHelper):
 
     def __init__(self, args):
@@ -204,13 +288,6 @@ class TestBlendLibAppendBasic(TestBlendLibLinkHelper):
         bpy.ops.wm.append(directory=link_dir, filename="LibMesh",
                           instance_object_data=False, set_fake=False, use_recursive=False, do_reuse_local_id=False)
 
-        print(
-            bpy.data.materials[:],
-            bpy.data.materials[0].library,
-            bpy.data.materials[0].users,
-            bpy.data.materials[0].use_fake_user,
-        )
-
         assert len(bpy.data.materials) == 1
         assert bpy.data.materials[0].library is not None
         assert bpy.data.materials[0].users == 2  # Fake user is not cleared when linking.
@@ -473,8 +550,11 @@ class TestBlendLibDataLibrariesLoad(TestBlendLibLinkHelper):
 
 TESTS = (
     TestBlendLibLinkSaveLoadBasic,
+    TestBlendLibLinkIndirect,
+
     TestBlendLibAppendBasic,
     TestBlendLibAppendReuseID,
+
     TestBlendLibLibraryReload,
     TestBlendLibLibraryRelocate,
     TestBlendLibDataLibrariesLoad,