asset_tag (module)

The assetTag field-constraint validator. Registers itself with field_constraints.module's registry on load so any component field carrying constraint = { kind = "assetTag", tag = ... } — which is exactly what Field.taggedRef emits — is checked against it.

What it does

Given a field's written value and its constraint:

1. Passes nil — an unset slot holds nothing to check.
2. Reads the value's identity — a bare string, or a table's __ref / guid / identity / name.
3. Resolves it as an asset of any type (asset.resolve(identity)), since the tag is the whole gate.
4. Answers asset.has_tag(identity, constraint.tag).

Acceptance rides on the tag rather than the asset's type, so an asset becomes assignable to a tagged slot the moment it is tagged — no edit to the field or to anything that reads it.

A rejection names the tag the slot wants, the tags the asset carries instead, and the asset.list({ fields = { tags = ... } }) call that enumerates what would fit, so the message carries its own next step.

Exports

• M.check(value, constraint) -> ok, reason? — the validator function, also registered under the assetTag kind.