fix: emit listing LastModified as RFC3339 'Z' (rclone rejects +00:00) (#94)

Author: ServerSideHannes

s3proxy/handlers/buckets.py

@@ -4,6 +4,7 @@
 import contextlib
 import uuid
 import xml.etree.ElementTree as ET
+from datetime import UTC, datetime
 from urllib.parse import parse_qs
 
 import structlog
@@ -24,6 +25,19 @@
 LIST_HEAD_CONCURRENCY = 50
 
 
+def _s3_timestamp(value: object) -> str:
+    """Format a listing timestamp as S3 does: RFC3339 in UTC with a 'Z' suffix.
+
+    datetime.isoformat() emits a '+00:00' offset, which strict S3 clients reject
+    — scylla-manager's rclone 1.51.0 fails the whole listing with "cannot parse
+    '+00:00' as 'Z'". Emit millisecond precision + 'Z' to match real S3.
+    """
+    if not isinstance(value, datetime):
+        return str(value)
+    d = value.astimezone(UTC)
+    return f"{d:%Y-%m-%dT%H:%M:%S}.{d.microsecond // 1000:03d}Z"
+
+
 def _strip_minio_cache_suffix(value: str | None) -> str | None:
     """Strip MinIO cache metadata suffix from marker/token values.
 
@@ -207,7 +221,7 @@ async def resolve(obj: dict) -> dict:
                     size, etag = obj.get("Size", 0), obj.get("ETag", "").strip('"')
             return {
                 "key": obj["Key"],
-                "last_modified": obj["LastModified"].isoformat(),
+                "last_modified": _s3_timestamp(obj["LastModified"]),
                 "etag": etag,
                 "size": size,
                 "storage_class": obj.get("StorageClass", "STANDARD"),
@@ -297,9 +311,7 @@ async def handle_list_multipart_uploads(
                     {
                         "Key": key,
                         "UploadId": upload.get("UploadId", ""),
-                        "Initiated": upload.get("Initiated", "").isoformat()
-                        if hasattr(upload.get("Initiated"), "isoformat")
-                        else str(upload.get("Initiated", "")),
+                        "Initiated": _s3_timestamp(upload.get("Initiated", "")),
                         "StorageClass": upload.get("StorageClass", "STANDARD"),
                     }
                 )

tests/unit/test_s3_timestamp.py

@@ -0,0 +1,35 @@
+"""Self-check: listing timestamps use S3's 'Z' UTC suffix, not '+00:00'.
+
+datetime.isoformat() emits '+00:00', which scylla-manager's rclone 1.51.0
+rejects ("cannot parse '+00:00' as 'Z'"), failing the whole ListObjects. S3
+itself returns millisecond-precision RFC3339 with a 'Z' suffix.
+"""
+
+from datetime import UTC, datetime, timezone
+
+from s3proxy.handlers.buckets import _s3_timestamp
+
+
+def test_utc_datetime_uses_z_suffix_millis():
+    d = datetime(2026, 6, 30, 10, 24, 43, 399000, tzinfo=UTC)
+    assert _s3_timestamp(d) == "2026-06-30T10:24:43.399Z"
+
+
+def test_non_utc_is_converted_to_utc_z():
+    from datetime import timedelta
+
+    d = datetime(2026, 6, 30, 12, 24, 43, 0, tzinfo=timezone(timedelta(hours=2)))
+    assert _s3_timestamp(d) == "2026-06-30T10:24:43.000Z"
+    assert "+" not in _s3_timestamp(d)
+
+
+def test_non_datetime_passthrough():
+    assert _s3_timestamp("") == ""
+    assert _s3_timestamp("already-a-string") == "already-a-string"
+
+
+if __name__ == "__main__":
+    test_utc_datetime_uses_z_suffix_millis()
+    test_non_utc_is_converted_to_utc_z()
+    test_non_datetime_passthrough()
+    print("ok")