Implemented reporting callbacks.

Both the dependency Tracer class and the Packer class now support a
callback object, where the latter is a subclass of the former.

For file transfers running in a separate thread, there is a thread-safe
wrapper for progress callbacks. This wrapper can be called from any thread,
and calls the wrapped callback object from the main thread. This way the
callback implementation itself doesn't have to worry about threading
issues.

tests/test_pack.py

@@ -1,8 +1,12 @@
 import logging
 import pathlib
+import typing
+
 import tempfile
+from unittest import mock
 
 from blender_asset_tracer import blendfile, pack, bpathlib
+from blender_asset_tracer.pack import progress
 from abstract_test import AbstractBlendFileTest
 
 
@@ -31,6 +35,12 @@ class AbstractPackTest(AbstractBlendFileTest):
                 for path, action in packer._actions.items()
                 if action.rewrites}
 
+    def outside_project(self) -> pathlib.Path:
+        """Return the '_outside_project' path for files in self.blendfiles."""
+        # /tmp/target + /workspace/bat/tests/blendfiles → /tmp/target/workspace/bat/tests/blendfiles
+        extpath = pathlib.Path(self.tpath, '_outside_project', *self.blendfiles.parts[1:])
+        return extpath
+
 
 class PackTest(AbstractPackTest):
     def test_strategise_no_rewrite_required(self):
@@ -69,8 +79,7 @@ class PackTest(AbstractPackTest):
             'textures/Bricks/brick_dotted_04-bump.jpg',
             'textures/Bricks/brick_dotted_04-color.jpg',
         )
-        # /tmp/target + /workspace/bat/tests/blendfiles → /tmp/target/workspace/bat/tests/blendfiles
-        extpath = pathlib.Path(self.tpath, '_outside_project', *self.blendfiles.parts[1:])
+        extpath = self.outside_project()
 
         act = packer._actions[ppath / 'doubly_linked_up.blend']
         self.assertEqual(pack.PathAction.KEEP_PATH, act.path_action, 'for doubly_linked_up.blend')
@@ -245,3 +254,102 @@ class PackTest(AbstractPackTest):
             self.tpath / self.blendfiles.name / infile.name,
             packer.output_path
         )
+
+
+class ProgressTest(AbstractPackTest):
+    def test_strategise(self):
+        cb = mock.Mock(progress.Callback)
+        infile = self.blendfiles / 'subdir/doubly_linked_up.blend'
+        with pack.Packer(infile, self.blendfiles, self.tpath) as packer:
+            packer.progress_cb = cb
+            packer.strategise()
+
+        self.assertEqual(1, cb.pack_start.call_count)
+        self.assertEqual(0, cb.pack_done.call_count)
+
+        expected_calls = [
+            mock.call(self.blendfiles / 'subdir/doubly_linked_up.blend'),
+            mock.call(self.blendfiles / 'linked_cube.blend'),
+            mock.call(self.blendfiles / 'basic_file.blend'),
+            mock.call(self.blendfiles / 'material_textures.blend'),
+        ]
+        cb.trace_blendfile.assert_has_calls(expected_calls, any_order=True)
+        self.assertEqual(len(expected_calls), cb.trace_blendfile.call_count)
+
+        expected_calls = [
+            mock.call(self.blendfiles / 'linked_cube.blend'),
+            mock.call(self.blendfiles / 'basic_file.blend'),
+            mock.call(self.blendfiles / 'material_textures.blend'),
+            mock.call(self.blendfiles / 'textures/Bricks/brick_dotted_04-color.jpg'),
+            mock.call(self.blendfiles / 'textures/Bricks/brick_dotted_04-bump.jpg'),
+        ]
+        cb.trace_asset.assert_has_calls(expected_calls, any_order=True)
+        self.assertEqual(len(expected_calls), cb.trace_asset.call_count)
+
+        self.assertEqual(0, cb.rewrite_blendfile.call_count)
+        self.assertEqual(0, cb.transfer_file.call_count)
+        self.assertEqual(0, cb.transfer_file_skipped.call_count)
+        self.assertEqual(0, cb.transfer_progress.call_count)
+        self.assertEqual(0, cb.missing_file.call_count)
+
+    def test_execute_with_rewrite(self):
+        cb = mock.Mock(progress.Callback)
+        infile = self.blendfiles / 'subdir/doubly_linked_up.blend'
+        with pack.Packer(infile, infile.parent, self.tpath) as packer:
+            packer.progress_cb = cb
+            packer.strategise()
+            packer.execute()
+
+        self.assertEqual(1, cb.pack_start.call_count)
+        self.assertEqual(1, cb.pack_done.call_count)
+
+        # rewrite_blendfile should only be called paths in a blendfile are
+        # actually rewritten.
+        cb.rewrite_blendfile.assert_called_with(self.blendfiles / 'subdir/doubly_linked_up.blend')
+        self.assertEqual(1, cb.rewrite_blendfile.call_count)
+
+        # mock.ANY is used for temporary files in temporary paths, because they
+        # are hard to predict.
+        extpath = self.outside_project()
+        expected_calls = [
+            mock.call(mock.ANY, self.tpath / 'doubly_linked_up.blend'),
+            mock.call(mock.ANY, extpath / 'linked_cube.blend'),
+            mock.call(mock.ANY, extpath / 'basic_file.blend'),
+            mock.call(mock.ANY, extpath / 'material_textures.blend'),
+            mock.call(self.blendfiles / 'textures/Bricks/brick_dotted_04-color.jpg',
+                      extpath / 'textures/Bricks/brick_dotted_04-color.jpg'),
+            mock.call(self.blendfiles / 'textures/Bricks/brick_dotted_04-bump.jpg',
+                      extpath / 'textures/Bricks/brick_dotted_04-bump.jpg'),
+        ]
+        cb.transfer_file.assert_has_calls(expected_calls, any_order=True)
+        self.assertEqual(len(expected_calls), cb.transfer_file.call_count)
+
+        self.assertEqual(0, cb.transfer_file_skipped.call_count)
+        self.assertGreaterEqual(cb.transfer_progress.call_count, 6,
+                                'transfer_progress() should be called at least once per asset')
+        self.assertEqual(0, cb.missing_file.call_count)
+
+    def test_missing_files(self):
+        cb = mock.Mock(progress.Callback)
+        infile = self.blendfiles / 'missing_textures.blend'
+        with pack.Packer(infile, self.blendfiles, self.tpath) as packer:
+            packer.progress_cb = cb
+            packer.strategise()
+            packer.execute()
+
+        self.assertEqual(1, cb.pack_start.call_count)
+        self.assertEqual(1, cb.pack_done.call_count)
+
+        cb.rewrite_blendfile.assert_not_called()
+        cb.transfer_file.assert_called_with(infile, self.tpath / 'missing_textures.blend')
+
+        self.assertEqual(0, cb.transfer_file_skipped.call_count)
+        self.assertGreaterEqual(cb.transfer_progress.call_count, 1,
+                                'transfer_progress() should be called at least once per asset')
+
+        expected_calls = [
+            mock.call(self.blendfiles / 'textures/HDRI/Myanmar/Golden Palace 2, Old Bagan-1k.exr'),
+            mock.call(self.blendfiles / 'textures/Textures/Marble/marble_decoration-color.png'),
+        ]
+        cb.missing_file.assert_has_calls(expected_calls, any_order=True)
+        self.assertEqual(len(expected_calls), cb.missing_file.call_count)