Topdata Inheritance Contract

Status Snapshot

Current state as of 2026-05-13:

Implemented.
native.go supports both row-sugar inheritance and generic object inheritance, including cycle detection and missing-target failures.
Validation and build regression coverage live in topdata_test.go.

Native topdata now supports two inheritance forms:

1. Row Sugar Compatibility

This is the existing narrow row helper:

{
  "PARENT": { "id": "custom:parent" },
  "inherit": {
    "from": "PARENT",
    "fields": ["VALUE", "ICON"]
  }
}

It remains supported for row-local field copying.

2. Generic Object Inheritance

This is the new reusable primitive:

{
  "inherit": {
    "ref": "masterfeats:skillfocus"
  },
  "LABEL": "FEAT_SKILL_FOCUS_ATHLETICS"
}

Or for a nested object:

{
  "DETAILS": {
    "inherit": {
      "ref": "custom:parent",
      "field": "DETAILS"
    },
    "meta": {
      "cost": "9"
    }
  }
}

Rules

inherit.ref must use stable dataset:key identity.
inherit.field is optional and selects an object-valued field on the target row.
Generic inheritance can appear on any authored object, not only top-level rows.
Merge precedence is local overrides inherited.
Scalars replace inherited values.
Arrays replace inherited values.
Objects merge recursively unless the local object is an atomic topdata value object such as:
- TLK payloads
- row refs
- table refs
Cycles fail the build.
Missing targets fail the build.

Current Intended Consumer

feat is the first dataset expected to use this primitive heavily, especially for borrowing shared properties from masterfeats while keeping feat's own dataset contract and row model.

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