Tests: Add coverage for in-place patching and metadata clearing

Signed-off-by: alighazi288 <51366992+alighazi288@users.noreply.github.com>

Author: alighazi288

src/borg/testsuite/archive_test.py

@@ -1,5 +1,6 @@
 import json
 import os
+import stat
 from collections import OrderedDict
 from datetime import datetime, timezone
 from io import StringIO
@@ -12,7 +13,7 @@
 from ..archive import Archive, CacheChunkBuffer, RobustUnpacker, valid_msgpacked_dict, ITEM_KEYS, Statistics
 from ..archive import BackupOSError, backup_io, backup_io_iter, get_item_uid_gid
 from ..helpers import msgpack
-from ..item import Item, ArchiveItem
+from ..item import Item, ArchiveItem, ChunkListEntry
 from ..manifest import Archives, Manifest
 from ..platform import uid2user, gid2group, is_win32
 
@@ -435,3 +436,167 @@ def test_archives_get_by_id_missing_returns_none():
     manifest = Mock()
     archives = Archives(repo, manifest)
     assert archives.get_by_id(b"\x01" * 32) is None
+
+
+# ---- borg extract: in-place chunk comparison / selective extraction (#5638) ----
+
+CHUNK_SIZE = 4
+
+
+class FetchManyPipeline:
+    """Minimal pipeline stand-in that records which chunk ids fetch_many() requested."""
+
+    def __init__(self, objects):
+        self.objects = objects  # id -> data
+        self.fetched = []
+
+    def fetch_many(self, chunks, ro_type=None):
+        assert ro_type is not None
+        for chunk in chunks:
+            self.fetched.append(chunk.id)
+            yield self.objects[chunk.id]
+
+
+@pytest.fixture
+def extractor(tmpdir):
+    repository = Mock()
+    key = PlaintextKey(repository)
+    manifest = Manifest(key, repository)
+    archive = Archive(manifest=manifest, name="test", create=True)
+    archive.key = key
+    archive.cwd = str(tmpdir)
+    return archive
+
+
+def make_item(key, objects, data):
+    """Chunk *data* into CHUNK_SIZE pieces, register them in *objects*, return an Item."""
+    chunks = []
+    for i in range(0, len(data), CHUNK_SIZE):
+        piece = data[i : i + CHUNK_SIZE]
+        cid = key.id_hash(piece)
+        chunks.append(ChunkListEntry(id=cid, size=len(piece)))
+        objects[cid] = piece
+    item = Item(path="test", mode=stat.S_IFREG | 0o644, size=len(data))
+    item.chunks = chunks
+    return item
+
+
+@pytest.mark.parametrize(
+    "name, item_data, fs_data, expected_fetched",
+    [
+        ("no_change", b"11112222", b"11112222", 0),
+        ("first_chunk", b"11112222", b"33332222", 1),
+        ("second_chunk", b"11112222", b"11113333", 1),
+        ("both_chunks", b"11112222", b"33334444", 2),
+        ("cross_boundary", b"11112222", b"11333322", 2),
+        ("partial_last_chunk", b"1111222233", b"1111222244", 1),
+        ("fs_shorter", b"11112222", b"111122", 1),
+        ("fs_longer", b"11112222", b"1111222233", 0),
+        ("empty_item", b"", b"11112222", 0),
+        ("empty_fs", b"11112222", b"", 2),
+    ],
+)
+def test_compare_and_extract_chunks(extractor, tmpdir, name, item_data, fs_data, expected_fetched):
+    objects = {}
+    item = make_item(extractor.key, objects, item_data)
+    pipeline = FetchManyPipeline(objects)
+    extractor.pipeline = pipeline
+    # we only exercise the data path here; attribute (re)storing is covered elsewhere.
+    extractor.clear_attrs = Mock()
+    extractor.restore_attrs = Mock()
+
+    path = str(tmpdir.join("test"))
+    with open(path, "wb") as f:
+        f.write(fs_data)
+    st = os.stat(path)
+
+    assert extractor.compare_and_extract_chunks(item, path, st=st)
+    assert len(pipeline.fetched) == expected_fetched
+    with open(path, "rb") as f:
+        assert f.read() == item_data
+
+
+def test_compare_and_extract_chunks_fetches_only_differing(extractor, tmpdir):
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    pipeline = FetchManyPipeline(objects)
+    extractor.pipeline = pipeline
+    extractor.clear_attrs = Mock()
+    extractor.restore_attrs = Mock()
+
+    path = str(tmpdir.join("test"))
+    with open(path, "wb") as f:
+        f.write(b"1111XXXX")  # only the second chunk differs
+
+    extractor.compare_and_extract_chunks(item, path, st=os.stat(path))
+    # exactly the (differing) second chunk should have been fetched, not the first.
+    assert pipeline.fetched == [item.chunks[1].id]
+
+
+@pytest.mark.parametrize("st_is_none", [True, False])
+def test_compare_and_extract_chunks_skips_non_regular(extractor, tmpdir, st_is_none):
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    extractor.pipeline = FetchManyPipeline(objects)
+    if st_is_none:
+        st = None
+    else:
+        st = os.stat(str(tmpdir))  # a directory, not a regular file
+    assert extractor.compare_and_extract_chunks(item, str(tmpdir.join("test")), st=st) is False
+
+
+def test_compare_and_extract_chunks_skips_hardlinks(extractor, tmpdir):
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    item.hlid = b"\x00" * 32  # a hard link must use the normal (preloaded) extraction path
+    path = str(tmpdir.join("test"))
+    with open(path, "wb") as f:
+        f.write(b"11112222")
+    assert extractor.compare_and_extract_chunks(item, path, st=os.stat(path)) is False
+
+
+def test_compare_and_extract_chunks_skips_hardlinked_file(extractor, tmpdir):
+    # a destination file with other hard links (st_nlink > 1) must not be patched in place,
+    # as that would change the content seen through those other links.
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    extractor.pipeline = FetchManyPipeline(objects)
+    path = str(tmpdir.join("test"))
+    with open(path, "wb") as f:
+        f.write(b"11112222")
+    os.link(path, str(tmpdir.join("other-link")))  # st_nlink becomes 2
+    assert extractor.compare_and_extract_chunks(item, path, st=os.stat(path)) is False
+
+
+def test_compare_and_extract_chunks_skips_file_with_extended_acl(extractor, tmpdir):
+    # a file carrying an extended ACL must not be patched in place, because clear_attrs() does
+    # not reset ACLs; such files fall back to normal extraction (fresh inode, clean metadata).
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    extractor.pipeline = FetchManyPipeline(objects)
+    extractor._fs_has_extended_acl = Mock(return_value=True)
+    path = str(tmpdir.join("test"))
+    with open(path, "wb") as f:
+        f.write(b"11112222")
+    assert extractor.compare_and_extract_chunks(item, path, st=os.stat(path)) is False
+
+
+@pytest.mark.skipif(is_win32, reason="xattrs/clear_attrs are POSIX-only")
+def test_compare_and_extract_chunks_clears_stale_xattr(extractor, tmpdir):
+    from .. import xattr as xattr_mod
+
+    path = str(tmpdir.join("test")).encode()
+    with open(path, "wb") as f:
+        f.write(b"oldcontent")
+    if not xattr_mod.is_enabled(str(tmpdir)):
+        pytest.skip("xattrs not supported on this filesystem")
+    xattr_mod.set_all(path, {b"user.stale": b"1"})
+
+    objects = {}
+    item = make_item(extractor.key, objects, b"11112222")
+    extractor.pipeline = FetchManyPipeline(objects)
+    extractor.restore_attrs = Mock()  # real clear_attrs, but skip restoring archived attrs
+
+    assert extractor.compare_and_extract_chunks(item, path.decode(), st=os.stat(path))
+    # the stale xattr that was not part of the archive item must be gone.
+    assert b"user.stale" not in xattr_mod.get_all(path)

src/borg/testsuite/archiver/extract_cmd_test.py

@@ -771,6 +771,32 @@ def test_extract_continue(archivers, request):
             assert f.read() == CONTENTS3
 
 
+def test_extract_patches_existing_file_in_place(archivers, request):
+    # when extracting over an existing regular file, borg updates it in place (only fetching
+    # the chunks that differ, see #5638) instead of unlinking and recreating it.
+    archiver = request.getfixturevalue(archivers)
+    # use a reasonably large, chunkable content so multiple chunks exist.
+    contents = os.urandom(4 * 1024 * 1024)
+    cmd(archiver, "repo-create", RK_ENCRYPTION)
+    create_regular_file(archiver.input_path, "file", contents=contents)
+    cmd(archiver, "create", "arch", "input")
+
+    with changedir("output"):
+        cmd(archiver, "extract", "arch")
+        st_before = os.stat("input/file")
+        # locally modify a few bytes near the start, leaving the rest identical.
+        with open("input/file", "rb+") as f:
+            f.seek(5)
+            f.write(b"DIFFERENT")
+        # extract again (no --continue): the existing file should be patched in place.
+        cmd(archiver, "extract", "arch")
+        st_after = os.stat("input/file")
+        if not is_win32:
+            assert st_before.st_ino == st_after.st_ino  # same inode -> updated in place
+        with open("input/file", "rb") as f:
+            assert f.read() == contents  # content fully restored
+
+
 def test_dry_run_extraction_flags(archivers, request):
     archiver = request.getfixturevalue(archivers)
     cmd(archiver, "repo-create", RK_ENCRYPTION)