LibraryOverrides: Initial Test Case.

Added a first test case for review. This will be the base for future test cases.

The current API is sufficient for what is expected for such a low level API.
One concern is that you need to trigger a save in order to update the library overrides
structure. Not expected from TD/Dev point of view.

Test cases are very important when implementing restrictive mode as it is a second evaluation mode that
has impact on the (current) permissive mode.

Reviewed By: Sebastián Barschkis, Bastien Montagne

Differential Revision: https://developer.blender.org/D10747

tests/python/CMakeLists.txt

@@ -154,6 +154,12 @@ add_blender_test(
   --output-dir ${TEST_OUT_DIR}/blendfile_io/
 )
 
+add_blender_test(
+  blendfile_library_overrides
+  --python ${CMAKE_CURRENT_LIST_DIR}/bl_blendfile_library_overrides.py --
+  --output-dir ${TEST_OUT_DIR}/blendfile_io/
+)
+
 # ------------------------------------------------------------------------------
 # MODELING TESTS
 add_blender_test(

tests/python/bl_blendfile_library_overrides.py

@@ -0,0 +1,107 @@
+# Apache License, Version 2.0
+
+# ./blender.bin --background -noaudio --python tests/python/bl_blendfile_library_overrides.py
+import pathlib
+import bpy
+import sys
+import os
+import unittest
+
+sys.path.append(os.path.dirname(os.path.realpath(__file__)))
+from bl_blendfile_utils import TestHelper
+
+
+class TestLibraryOverrides(TestHelper, unittest.TestCase):
+    MESH_LIBRARY_PARENT = "LibMeshParent"
+    OBJECT_LIBRARY_PARENT = "LibMeshParent"
+    MESH_LIBRARY_CHILD = "LibMeshChild"
+    OBJECT_LIBRARY_CHILD = "LibMeshChild"
+
+    def __init__(self, args):
+        self.args = args
+
+        output_dir = pathlib.Path(self.args.output_dir)
+        self.ensure_path(str(output_dir))
+        self.output_path = output_dir / "blendlib_overrides.blend"
+        self.test_output_path = output_dir / "blendlib_overrides_test.blend"
+
+        bpy.ops.wm.read_homefile(use_empty=True, use_factory_startup=True)
+        mesh = bpy.data.meshes.new(TestLibraryOverrides.MESH_LIBRARY_PARENT)
+        obj = bpy.data.objects.new(TestLibraryOverrides.OBJECT_LIBRARY_PARENT, object_data=mesh)
+        bpy.context.collection.objects.link(obj)
+        mesh_child = bpy.data.meshes.new(TestLibraryOverrides.MESH_LIBRARY_CHILD)
+        obj_child = bpy.data.objects.new(TestLibraryOverrides.OBJECT_LIBRARY_CHILD, object_data=mesh_child)
+        obj_child.parent = obj
+        bpy.context.collection.objects.link(obj_child)
+        bpy.ops.wm.save_as_mainfile(filepath=str(self.output_path), check_existing=False, compress=False)
+
+    def __ensure_override_library_updated(self):
+        # During save the override_library is updated.
+        bpy.ops.wm.save_as_mainfile(filepath=str(self.test_output_path), check_existing=False, compress=False)
+
+    def test_link_and_override_property(self):
+        bpy.ops.wm.read_homefile(use_empty=True, use_factory_startup=True)
+        bpy.data.orphans_purge()
+
+        link_dir = self.output_path / "Object"
+        bpy.ops.wm.link(directory=str(link_dir), filename=TestLibraryOverrides.OBJECT_LIBRARY_PARENT)
+
+        obj = bpy.data.objects[TestLibraryOverrides.OBJECT_LIBRARY_PARENT]
+        assert(obj.override_library is None)
+        local_id = obj.override_create()
+        assert(local_id.override_library)
+        assert(local_id.data.override_library is None)
+        assert(len(local_id.override_library.properties) == 0)
+
+        local_id.location.y = 1.0
+
+        self.__ensure_override_library_updated()
+
+        assert (len(local_id.override_library.properties) == 1)
+        assert(len(local_id.override_library.properties) == 1)
+        override_prop = local_id.override_library.properties[0]
+        assert(override_prop.rna_path, "location");
+        assert(len(override_prop.operations) == 1)
+        override_operation = override_prop.operations[0]
+        assert (override_operation.operation == 'REPLACE')
+        # Setting location.y overridded all elements in the location array. -1 is a wildcard.
+        assert(override_operation.subitem_local_index == -1)
+        
+
+TESTS = (
+    TestLibraryOverrides,
+)
+
+
+def argparse_create():
+    import argparse
+
+    # When --help or no args are given, print this help
+    description = "Test library overrides of blend file."
+    parser = argparse.ArgumentParser(description=description)
+    parser.add_argument(
+        "--output-dir",
+        dest="output_dir",
+        default=".",
+        help="Where to output temp saved blendfiles",
+        required=False,
+    )
+
+    return parser
+
+
+def main():
+    args = argparse_create().parse_args()
+
+    # Don't write thumbnails into the home directory.
+    bpy.context.preferences.filepaths.use_save_preview_images = False
+
+    for Test in TESTS:
+        Test(args).run_all_tests()
+
+
+if __name__ == '__main__':
+    import sys
+    sys.argv = [__file__] + \
+        (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])
+    main()