jmap-metadata-types

Serde-annotated Rust types for the JMAP Object Metadata extension (draft-ietf-jmap-metadata-04). Types only — no method handlers, no async, no network I/O.

What it is

What it's for

Shared vocabulary for jmap-metadata-server (server-side helpers) and jmap-metadata-client (client-side helpers). This crate is the foundation of the workspace-recommended IETF-track escape hatch for vendor data that needs to be queryable: the workspace extras-preservation policy excludes filter algebra (silent-drop is a query-correctness bug), so vendors who need filterable data put it in a namespace under metadata / privateMetadata rather than in a vendor-extended filter condition.

Why this crate exists

jmap-types and the extension-types crates apply an extras-preservation policy that captures vendor fields in a flatten extra map on every wire-format Deserialize struct. That policy explicitly excludes filter and comparator algebra: silently round-tripping an unknown filter clause through the client gives the wrong record set back with no error signal.

draft-ietf-jmap-metadata-04 is the IETF-track answer. Each data type a server lists in the capability's dataTypes gains two properties, metadata (shared) and privateMetadata (per-user), whose values are objects keyed by namespace identifier (§2). Clients read and write them through the data type's own /get and /set, and search them through six metadata* / privateMetadata* conditions on the data type's own /query filter (§3). There is no standalone Metadata object and no Metadata/* method.

Spec coverage

draft-ietf-jmap-metadata-04 sections implemented:

• §1.2.1 — DataTypeMetadataInfo and JMAP_METADATA_URI
• §2.1 — namespace identifier validation
• §3.6 — MetadataTextMatch

Not in this crate:

• Depth counting (§2.1), namespace-support checks (§3.1, §3.2), filter predicates (§3.6), and /changes classification (§3.3) — pure helpers in jmap-metadata-server.
• Filter-condition builders and property-name constants — jmap-metadata-client.
• Typed metadata / privateMetadata fields on the extension-types data objects. By decision (bd JMAP-ua37.4) both properties round-trip through each object's extra map instead.

How to use

use jmap_metadata_types::{DataTypeMetadataInfo, is_registered_namespace};

// The "FileNode" entry of the §6.1 capability example.
let info: DataTypeMetadataInfo = serde_json::from_str(r#"{
    "namespaces": ["photography"],
    "supportsVendorNamespaces": false,
    "supportsPrivate": false,
    "maxDepth": 3
}"#).unwrap();

assert_eq!(info.namespaces, vec!["photography"]);
assert!(!info.supports_vendor_namespaces);
assert_eq!(info.max_depth, Some(3));
assert!(is_registered_namespace("photography"));

How it works

DataTypeMetadataInfo uses #[serde(rename_all = "camelCase")], with #[serde(default)] on the three fields the draft gives defaults (namespaces, supportsVendorNamespaces, supportsPrivate). maxDepth is Option<u64>; None is the draft's null (no server-enforced limit).

The namespace predicates check syntax only. Whether a namespace is supported on a data type depends on the capability and lives in jmap_metadata_server::is_namespace_supported.

Gotchas

Tests are named with _draft_02_ where they pin a specific draft example (written from -02; -04 keeps those examples). When the draft revs, expect to update or replace these tests alongside the wire-format changes. The #[non_exhaustive] derive on every struct keeps additive spec evolution non-breaking, but a renamed or removed wire field is still a breaking change in the next 0.x bump.

MetadataTextMatch and DataTypeMetadataInfo carry no extra field: the first is filter algebra and the second is a capability object, both outside the extras-preservation policy (see the workspace AGENTS.md).

References

• draft-ietf-jmap-metadata-04 — JMAP Object Metadata (normative for all type definitions)
• RFC 8620 — JMAP Core (capabilities object, /get, /set, /query)