PUT path drops JSON object key ordering — breaks drag-reorder UX in object-keyed schemas

[rubenvdlinde]

Repro

Against /api/objects/openconnector/mapping/<id>:

1. Object stored as {mapping: {beta: 'x', alpha: 'y', gamma: 'z'}}
2. Send PUT with {mapping: {zeta: 'a', alpha: 'b', beta: 'c', gamma: 'd'}}
3. GET returns {mapping: {beta: 'c', zeta: 'a', alpha: 'b', gamma: 'd'}}

The client-supplied key order is dropped. Existing keys retain their storage order, new keys get inserted between them.

Effect

Surfaced during openconnector PR #903 (drag-reorder rules in MappingDetailPage). The drag UI works in-session — local Vue state reorders, the PUT fires with the new order — but on the next GET the storage returns the keys in its own order, snapping the visible list back. Users drag, save, reload, see the old order. Confusing.

Mapping/cast/rule schemas use object-keyed shapes ({targetProp: template}) where order matters semantically (cascading transformations). Array-shaped fields like unset are unaffected.

Root cause hypothesis

OR's PUT path likely stores the JSON via PHP json_decode($x, true) → associative array → re-encodes on GET. Associative arrays in PHP preserve insertion order, so the dropping likely happens at the column-level merge step (existing keys get UPDATE, new keys get INSERT, then GET sorts by some default ordering).

Worth tracing in lib/Service/ObjectService::saveObject and the storage layer below.

Fix options

1. Preserve client-supplied object key order by serializing the full object verbatim on PUT and storing as a single JSON column — no column-level diff. Most accurate fix, biggest blast radius.
2. Add an _order sidecar metadata field on objects whose schema declares ordered keys (could be x-openregister-ordered-keys: true on the property). MappingService etc. honor it on read. Backward-compatible.
3. Schema migration: switch mapping/cast to array-of-{property, template} pairs. Cleanest data model but breaking change for every existing mapping object.

Acceptance

curl -X PUT ... -d '{"mapping":{"zeta":1,"alpha":2,"beta":3}}' && curl ... returns keys in the same order: zeta, alpha, beta.

Caller

Tracked in openconnector#876 (drag-reorder follow-up to #874's MappingDetailPage).