Add collection_diff util

src/kinto_http/utils.py

@@ -92,3 +92,21 @@ def records_equal(a, b):
     ac = {k: v for k, v in a.items() if k not in ignore_fields}
     bc = {k: v for k, v in b.items() if k not in ignore_fields}
     return ac == bc
+
+
+def collection_diff(src, dest):
+    """
+    Compare two lists of records.
+    """
+    dest_by_id = {r["id"]: r for r in dest}
+    to_create = []
+    to_update = []
+    for r in src:
+        record = dest_by_id.pop(r["id"], None)
+        if record is None:
+            to_create.append(r)
+        elif not records_equal(r, record):
+            r.pop("last_modified", None)
+            to_update.append((record, r))
+    to_delete = list(dest_by_id.values())
+    return to_create, to_update, to_delete

tests/test_utils.py

@@ -179,3 +179,61 @@ def test_records_equal_only_ignored_fields():
     a = {"last_modified": 123, "schema": "v1"}
     b = {"last_modified": 456, "schema": "v2"}
     assert utils.records_equal(a, b)
+
+
+def test_collection_diff_create():
+    src = [{"id": 1, "name": "Alice"}]
+    dest = []
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == [{"id": 1, "name": "Alice"}]
+    assert to_update == []
+    assert to_delete == []
+
+
+def test_collection_diff_update():
+    src = [{"id": 1, "name": "Alice"}]
+    dest = [{"id": 1, "name": "Bob"}]
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == []
+    assert to_update == [({"id": 1, "name": "Bob"}, {"id": 1, "name": "Alice"})]
+    assert to_delete == []
+
+
+def test_collection_diff_delete():
+    src = []
+    dest = [{"id": 1, "name": "Alice"}]
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == []
+    assert to_update == []
+    assert to_delete == [{"id": 1, "name": "Alice"}]
+
+
+def test_collection_diff_mixed():
+    src = [{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}, {"id": 3, "name": "Charlie"}]
+    dest = [
+        {"id": 2, "name": "Bob"},
+        {"id": 3, "name": "CharlieUpdated"},
+        {"id": 4, "name": "Dave"},
+    ]
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == [{"id": 1, "name": "Alice"}]
+    assert to_update == [({"id": 3, "name": "CharlieUpdated"}, {"id": 3, "name": "Charlie"})]
+    assert to_delete == [{"id": 4, "name": "Dave"}]
+
+
+def test_collection_diff_no_changes():
+    src = [{"id": 1, "name": "Alice"}]
+    dest = [{"id": 1, "name": "Alice"}]
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == []
+    assert to_update == []
+    assert to_delete == []
+
+
+def test_collection_diff_empty_collections():
+    src = []
+    dest = []
+    to_create, to_update, to_delete = utils.collection_diff(src, dest)
+    assert to_create == []
+    assert to_update == []
+    assert to_delete == []