xl.meta roundtrip coverage was one fixed example test plus byte-level no-panic
fuzz properties; nothing generated STRUCTURED version graphs, so a lossy
encoding bug in version headers, ordering, delete markers, or the dual
internal-metadata-key handling would only surface if the fixed example happened
to hit it.
Add crates/filemeta/tests/version_graph_roundtrip_proptest.rs with two
generated-input properties over multi-version graphs (1-7 versions, ~30% delete
markers, deliberately colliding mod_times to exercise tie-break ordering, user
metadata, and the AGENTS.md dual x-rustfs-internal-*/x-minio-internal-* keys
written via the real insert_bytes helper):
- version_graph_marshal_load_roundtrip: marshal -> load preserves version
count, meta_ver, the exact (id, type) sequence, full headers, fully decoded
per-version content, delete-marker payload shape, and both internal metadata
key forms with identical values.
- version_graph_marshal_is_idempotent: marshal(load(marshal(x))) is
byte-identical to marshal(x), catching encoders that mutate or reorder state
on the way out.
Complements the existing byte-level no-panic properties: those prove hostile
bytes cannot crash the decoder; these prove honest graphs are encoded
losslessly.
Refs: backlog#1151 (sec-10)
Zhengchao An