Module fields 

Typed metadata fields: the developer-facing view of a group’s AppData dictionary.

xmtp_mls’s MlsGroup metadata-field methods (metadata_fields, metadata_values, user_data, update_metadata_field, update_user_data, …) read and write application and public well-known components here. The bindings do not expose them yet. Everything is a pure function of one committed dictionary: a FieldSnapshot lists the fields its registry describes, decodes their values, and encodes writes. Nothing here consults the network or storage.

• MetadataFieldRef names a field: its component ID plus a label. The well-known constants (MetadataFieldRef::GROUP_NAME, …) cover the public well-known fields. The core resolves a ref by ID only.
• MetadataFieldDescriptor describes a listed field: its ref, MetadataComponentType, and committed permissions.
• FieldValue, FieldKey, and MetadataValue carry typed values; MetadataFieldValue and UserFieldValue pair them with a ref.
• ComponentMutation and UserFieldUpdate describe writes. FieldSnapshot::field_write and FieldSnapshot::user_data_writes encode them as FieldWrites, and FieldSnapshot::resolve_writes turns those into AppDataUpdate operations against a dictionary.

Authority

The committed registry is the only authority for a field’s existence and policy. A well-known field’s type is fixed by the protocol (component_type); an application field’s type is its registry entry’s tag. The backend catalogue only supplies the label of an application field and so the name that FieldSnapshot::field matches. A registry entry that does not decode is preserved in the dictionary but is not a field.

Structs

FieldSnapshot

The metadata fields of one dictionary and their values.

FieldWrite

An encoded write, fixed to the type it was encoded under. FieldSnapshot::resolve_writes refuses it if the field’s type changed.

MapEntry

MetadataFieldDescriptor

A field listed by FieldSnapshot::fields.

MetadataFieldRef

Names a metadata field: its component ID and, when one exists, its well-known or backend catalogue name.

MetadataFieldValue

A field and its value, absent when the group holds none.

UserFieldUpdate

Set (Some) or clear (None) the caller’s own entry of a user field.

UserFieldValue

One inbox’s value of a user field.

Enums

ComponentMutation

A write to one field. Map and set deltas apply atomically: an Insert of a present key, or an Update or Delete of an absent key, rejects the whole commit.

FieldError

FieldKey

A map or set key.

FieldValue

A scalar value or map value.

MapMutation

One key-level change to a map field.

MetadataComponentType

The shape of a field’s value.

MetadataKeyType

The type of a map or set key.

MetadataScalarType

The type of a scalar field or of a map value.

MetadataValue

A decoded field value.

SetMutation

One key-level change to a set field.

WriteOperation