Feat: Python Struct - Transform Functions Implementation

[Jose-Perigolo]

Changes

• Transform EACH

  • ..n (current item): Skip descent when the template key is missing in the data so dparent stays on the current EACH item and ..n resolves correctly (e.g. {x0:{y0:'..n'}} with data: {a0:[{n:0},{n:1}]}).
  • .x / ...v: Correct handling of one-dot (current) and three-dot (ascend to data root) relative paths inside EACH.
  • EACH over dict with list child: When the child template from $REF is a list, only set S_DMETA on map children to avoid TypeError on list indices.

• Transform PACK

  • Relative path resolution for paths like ...v100 and .y inside PACK now works via the shared getpath fixes.

• getpath relative paths

  • Leading-dot count: Count the current part as the first dot so .x, .., and ..key are interpreted correctly.
  • Two dots: .. only → ascend 1 (parent); ..key in transform (with base) → current then .key; in getpath_relative (no base) → ascend 1 then .key.
  • Three dots: ... only (4 parts) or ...key → ascend to data/store root; with base (e.g. $TOP) use size(dpath)-1, without base use size(dpath).
  • Path ..: Two dots produce 3 split parts; decrement twice so the effective ascend is 1 (parent).
  • Past root: When ascends > size(dpath) return UNDEF (e.g. ....).
  • Three-dots override: Skip the normal “last part” decrement when the three-dots ascend-to-root override was applied.

• descend()

  • Skip descent for any key missing from dparent (not only list indices), so template-only keys (e.g. x0, y0) do not overwrite dparent and ..n still resolves.

Tests

• All 9 transform tests pass (basic, cmds, each, extra, funcval, modify, pack, paths, ref).
• getpath_relative passes; no regressions in previously passing tests (52 passed total).