Usd Listops Authored

usd-listops-authored

Use this skill when implementing authored list operation values as they appear in a single layer.

Spec Sources

• specification/foundational_data_types/README.md section List Operations
• specification/file_formats/README.md section A General Note on Listops

Pinned tag / commit: v1.0.1

Provides

• Explicit listOp items
• Prepended listOp items
• Appended listOp items
• Deleted listOp items
• None as empty listOp outside attribute value assignment
• Last-one-wins behavior for repeated same listOp subfield

Contract

This skill owns contracts/handles/listops-authored.handle.json and stores authored list operations. It does not combine list operations across layer opinions.

Implementations should keep listOps in native authored storage with one item list per authored subfield: explicit, prepend, append, and delete. Tagged JSON is only the adapter/dump representation and should be materialized on demand.

The core listOp value model stores typed items, not parsed strings. The native item representation is:

• ObjectPath: path handle/reference from usd-paths
• Reference: native reference arc record with optional asset reference, optional prim path handle, offset, and scale
• Payload: native payload arc record with optional asset reference, optional prim path handle, offset, and scale
• token: token handle/reference from usd-tokens
• string: native string
• int/int64/uint/uint64: fixed-width integer values

Canonical dump shape:

{
  "type": "listop<ObjectPath>",
  "value": {
    "explicit": ["/A"],
    "prepend": [],
    "append": [],
    "delete": []
  }
}

Boundary Guards

Defer item equality for paths to usd-paths.

Defer token identity to usd-tokens.

Defer scalar eligibility and integer width/range rules to usd-foundational-values.

Do not implement cross-layer listOp composition or value resolution.

Do not retain tagged JSON as the backing listOp representation.

Do not parse USDA text syntax in this capability. USDA syntax belongs to the USDA parser skills.

Do not make JSON parsing or JSON-number/string coercion part of the core listOp model. JSON coercion belongs only in the handle adapter.

Do not store ObjectPath, token, or numeric listOp items as durable strings. Strings are the native storage type only for listOp<string>.

Do not store listOp<Reference> or listOp<Payload> items as dictionaries, bare asset strings, or bare path strings. Those shapes are parser input or dump-adapter output only; the domain item is a typed arc record.

Test Obligations

• implicit explicit listOp from a single authored list
• append/prepend/delete syntax
• repeated same subfield last-one-wins
• empty listOp defaults
• object path item validation through usd-paths
• reference and payload arc item storage as typed native records, not strings or dictionaries
• foundational element type validation for token, string, int, int64, uint, and uint64
• all cases in goldens/unit/usd-listops-authored/listops-authored.json