jmap-metadata-client

What it is

Pure, stateless client-side helpers for the JMAP Object Metadata extension (draft-ietf-jmap-metadata-02). No SessionClient, no extension trait, no network I/O. Depends only on jmap-metadata-types and serde_json.

What it's for

draft-02 has no standalone Metadata object and no Metadata/* methods. Metadata is read and written through metadata / privateMetadata properties on each opted-in data type, using that type's own methods (§3). Use these helpers alongside the typed extension clients (jmap-mail-client, jmap-calendars-client, …):

Helper	Use	Draft §
`METADATA_PROPERTY`, `PRIVATE_METADATA_PROPERTY`	names for a `Foo/get` `properties` list	§2, §3.1
`IGNORE_METADATA_ONLY_CHANGES`	`Foo/changes` request argument name	§3.3
`is_metadata_property`, `is_metadata_only_change`	classify a `Foo/changes` `updatedProperties` value	§3.3
`metadata_exists_condition`, `private_metadata_exists_condition`	`metadataExists` / `privateMetadataExists` filter conditions	§3.5
`metadata_text_contains_condition`, `private_metadata_text_contains_condition`	`metadataTextContains` / `privateMetadataTextContains`	§3.5
`metadata_text_equals_condition`, `private_metadata_text_equals_condition`	`metadataTextEquals` / `privateMetadataTextEquals`	§3.5

JMAP_METADATA_URI, DataTypeMetadataInfo, MetadataTextMatch, and the namespace validators are re-exported from jmap-metadata-types.

How to use

use jmap_metadata_client::{metadata_text_contains_condition, METADATA_PROPERTY};
use serde_json::json;

// Fetch an object's shared metadata alongside other properties (§3.1).
let properties = vec!["id", "name", METADATA_PROPERTY];
assert!(properties.contains(&"metadata"));

// Compose a metadata condition with the type's own conditions (§3.5).
// An extension client's `*_query` method takes it as
// `jmap_types::query::Filter::Condition(filter)`; for a typed tree, use
// `jmap_metadata_types::WithMetadata<C>` leaves instead.
let filter = json!({
    "operator": "AND",
    "conditions": [
        { "inMailbox": "MB-inbox" },
        metadata_text_contains_condition("acme.example.com/memo", "follow up"),
    ]
});
assert_eq!(
    filter["conditions"][1],
    json!({ "metadataTextContains": { "path": "acme.example.com/memo", "value": "follow up" } })
);

Gotchas

Pinned to draft-02. draft-02 was a complete rewrite of -01; later revisions (or a final RFC) may change the wire shape again.
Capability-dependent conditions. Any privateMetadata* condition is rejected with unsupportedFilter when the data type's supportsPrivate is false; servers MAY reject the four text-match conditions with unsupportedFilter and clients SHOULD be prepared to fall back to a client-side scan (§3.5). Check DataTypeMetadataInfo in the account capability first.
Typed filters. The extension-types FilterCondition structs carry no metadata fields (bd JMAP-ua37.4). The extension clients' *_query / *_query_changes methods take a generic jmap_types::query::Filter<C>, so a typed tree uses jmap_metadata_types::WithMetadata<C> leaves and an untyped one is passed as Filter::Condition(value). The chat client's *_query methods build their filter from *QueryInput fields and cannot carry metadata conditions; its *_query_changes methods can.

Migration from 0.1 (draft-01)

The 0.1 crate exposed JmapMetadataExt, SessionClient, metadata_get, metadata_changes, metadata_set, metadata_query, metadata_query_changes, and their parameter structs. All are removed in 0.2.

Crate family

jmap-metadata-types
    └── jmap-metadata-client  ← this crate

References

draft-ietf-jmap-metadata-02 — JMAP Object Metadata (normative for property names, the /changes argument, and filter conditions).
RFC 8620 — JMAP Core (/get, /changes, /query, filter operators).

jmap-metadata-client 0.3.0