The storage engine embedded a ~8.4K-line hand-written S3 HTTP client under crates/ecstore/src/client (rustfs/backlog#1842). That client is a legitimate engine capability — it consumes remote S3-compatible endpoints for ILM tier warm backends and transition targets — but it was misfiled inside the engine, dragging s3s/hyper wire types into ecstore and blocking ARCHITECTURE.md invariant 4.
This PR is the pure-move step: 21 modules move verbatim to the new crates/s3-client crate (rustfs-s3-client), and crates/ecstore/src/client/mod.rs becomes a re-export shim so every in-crate crate::client:: path keeps working. The two server-side modules that were historically misfiled under client/ — object_api_utils.rs and object_handlers_common.rs — stay in ecstore.
Three reverse dependencies from the client into engine internals are severed so the move can be pure:
- transition_api::ReaderImpl::ObjectBody held ecstore's GetObjectReader; the client only ever reads the body, so the variant now holds an ObjectReader newtype over Box<dyn AsyncRead + Send + Sync + Unpin> with the same read_all() surface. The single production construction site (set_disk transition upload) and the two engine-side consumers were adjusted.
- api_list/api_remove used ecstore's storage_api_contracts / object_api types; api_list now imports BucketInfo from rustfs-storage-api directly, and api_remove uses the client's own transition_api::ObjectInfo (only .name/.version_id were read; the error-path bucket name is now threaded as a parameter instead of read from the deleted objects).
- the api_put_object_streaming regression tests built a GetObjectReader by hand; they now wrap the duplex stream in ObjectReader::new.
Guard updates: the s3s footprint ratchet gains an ecstore-scoped counter (42 files, shrink-only, per rustfs/backlog#1842), the ecstore module-lint-blanket register follows the moved files into crates/s3-client so the blanket ratchet keeps covering them, the logging guardrail path pin follows transition_api.rs, and the ::other(format!) baseline is regenerated (moved call sites left ecstore).
Verification: cargo check -p rustfs-s3-client -p rustfs-ecstore; cargo nextest run -p rustfs-s3-client (43 passed) and -p rustfs-ecstore (4515/4523; the 8 failures reproduce identically on pristine origin/main on the same machine); cargo clippy --all-targets; scripts/check_layer_dependencies.sh, check_architecture_migration_rules.sh, check_s3s_footprint.sh, check_logging_guardrails.sh, check_error_other_format_ratchet.sh, check_doc_paths.sh, check_ci_paths_sync.sh all pass.
backlog#1823 step 9. The step 2 burn-down cleared every module-level #![allow(dead_code)] from ecstore, but nothing stops the next PR from adding one back, and the other module-level blankets (unused_variables, unused_must_use, clippy::all) were never counted at all.
Two rules land in check_architecture_migration_rules.sh:
ecstore must carry zero module-level #![allow(dead_code)]. The count is asserted at zero rather than registered, since there is nothing left to grandfather; a genuinely unused item takes an item-level allow with a reason, which is what step 2 produced roughly 350 times.
Every other module-level blanket must match scripts/ecstore-module-lint-register.txt exactly — 94 entries across 33 files, nearly all of them in the MinIO-ported client module.
The exact match is the point. A "no new entries" rule lets the register rot into an amnesty list, which is the failure mode backlog#1834 found in the layer-dependency baseline: rebuilt at 29 entries, 2 more added by a later PR, zero retired. Here, removing a blanket costs one line in the register, so it can only shrink, and adding one shows up as a register line a reviewer has to accept.
Verified by injection, since a guard that cannot fail is worse than no guard: adding a dead_code blanket, adding an unregistered clippy::all blanket, and deleting a registered blanket without updating the register each produce the expected failure, and the tree passes once reverted.
make pre-commit exit 0.
Ref rustfs/backlog#1823 (step 9).
Zhengchao An