feat: implement len(DirectorySnapshotDiff) to return the total number of changes

Author: BoboTiG

changelog.rst

@@ -10,6 +10,7 @@ Changelog
 
 - Adjust ``Observer.schedule()`` ``path`` type annotation to reflect the ``pathlib.Path`` support. (`#1096 <https://github.com/gorakhargosh/watchdog/pull/1096>`__)
 - [utils] Fixed ``repr(EmptyDirectorySnapshot)``, before that it was throwing an ``AttributeError: 'EmptyDirectorySnapshot' object has no attribute '_stat_info'``.
+- [utils] Implemented ``len(DirectorySnapshotDiff)`` to return the total number of changes.
 - Thanks to our beloved contributors: @BoboTiG, @tybug
 
 **Breaking Changes**

src/watchdog/utils/dirsnapshot.py

@@ -153,6 +153,9 @@ def __repr__(self) -> str:
             len(self._dirs_moved),
         )
 
+    def __len__(self) -> int:
+        return sum(len(getattr(self, attr)) for attr in dir(self) if attr.startswith(("_dirs_", "_files_")))
+
     @property
     def files_created(self) -> list[bytes | str]:
         """List of files that were created."""

tests/test_snapshot_diff.py

@@ -38,6 +38,7 @@ def test_move_to(p):
     ref = DirectorySnapshot(p("dir2"))
     mv(p("dir1", "a"), p("dir2", "b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("dir2")))
+    assert len(diff) == 2
     assert diff.files_created == [p("dir2", "b")]
 
 
@@ -51,6 +52,8 @@ def test_move_to_with_context_manager(p):
     with dir1_cm, dir2_cm:
         mv(p("dir1", "a"), p("dir2", "b"))
 
+    assert len(dir1_cm.diff) == 2
+    assert len(dir2_cm.diff) == 2
     assert dir1_cm.diff.files_deleted == [p("dir1", "a")]
     assert dir2_cm.diff.files_created == [p("dir2", "b")]
 
@@ -62,6 +65,7 @@ def test_move_from(p):
     ref = DirectorySnapshot(p("dir1"))
     mv(p("dir1", "a"), p("dir2", "b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("dir1")))
+    assert len(diff) == 2
     assert diff.files_deleted == [p("dir1", "a")]
 
 
@@ -72,6 +76,7 @@ def test_move_internal(p):
     ref = DirectorySnapshot(p(""))
     mv(p("dir1", "a"), p("dir2", "b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("")))
+    assert len(diff) == 3
     assert diff.files_moved == [(p("dir1", "a"), p("dir2", "b"))]
     assert diff.files_created == []
     assert diff.files_deleted == []
@@ -85,6 +90,7 @@ def test_move_replace(p):
     ref = DirectorySnapshot(p(""))
     mv(p("dir1", "a"), p("dir2", "b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("")))
+    assert len(diff) == 3
     assert diff.files_moved == [(p("dir1", "a"), p("dir2", "b"))]
     assert diff.files_deleted == [p("dir2", "b")]
     assert diff.files_created == []
@@ -95,6 +101,7 @@ def test_dir_modify_on_create(p):
     wait()
     touch(p("a"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("")))
+    assert len(diff) == 2
     assert diff.dirs_modified == [p("")]
 
 
@@ -106,6 +113,7 @@ def test_dir_modify_on_move(p):
     wait()
     mv(p("dir1", "a"), p("dir2", "b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("")))
+    assert len(diff) == 3
     assert set(diff.dirs_modified) == {p("dir1"), p("dir2")}
 
 
@@ -116,6 +124,7 @@ def test_detect_modify_for_moved_files(p):
     touch(p("a"))
     mv(p("a"), p("b"))
     diff = DirectorySnapshotDiff(ref, DirectorySnapshot(p("")))
+    assert len(diff) == 3
     assert diff.files_moved == [(p("a"), p("b"))]
     assert diff.files_modified == [p("a")]
 
@@ -159,6 +168,7 @@ def walk(self, root):
 
     diff = DirectorySnapshotDiff(ref, new_snapshot)
     assert repr(diff)
+    assert len(diff) == 1
 
     # Children of a/b/ are no more accessible and so removed in the new snapshot
     assert diff.dirs_deleted == [(p("a", "b", "c"))]
@@ -189,13 +199,15 @@ def inode(self, path):
         # be different), it thinks that the same file has been deleted and created again.
         snapshot = DirectorySnapshot(p(""))
         diff_with_device = DirectorySnapshotDiff(ref, snapshot)
+        assert len(diff_with_device) == 4
         assert diff_with_device.files_deleted == [(p("file"))]
         assert diff_with_device.files_created == [(p("file"))]
 
         # Otherwise, if we choose to ignore the device, the file will not be detected as
         # deleted and re-created.
         snapshot = DirectorySnapshot(p(""))
         diff_without_device = DirectorySnapshotDiff(ref, snapshot, ignore_device=True)
+        assert not len(diff_without_device)
         assert diff_without_device.files_deleted == []
         assert diff_without_device.files_created == []
 
@@ -213,5 +225,6 @@ def test_empty_snapshot(p):
     assert repr(empty) == "{}"
 
     diff = DirectorySnapshotDiff(empty, ref)
+    assert len(diff) == 4
     assert diff.files_created == [p("a")]
     assert sorted(diff.dirs_created) == sorted([p(""), p("b"), p("b", "c")])