Struct SourceRegistration 

pub struct SourceRegistration {
    pub spec: SourceSpec,
    pub kind: CandidateSourceKind,
    pub accept: Option<Arc<dyn AcceptHandler>>,
    pub matcher_override: Option<MatcherId>,
    pub ranker_overrides: Vec<RankerId>,
    pub annotator_extras: Vec<AnnotatorId>,
}

The substrate: bundle of every input the pipeline needs to produce + dispatch a source’s candidates.

Lives in lattice-completion (the abstraction layer); the host (lattice-host) holds the per-app CompletionRegistry and stores registrations there. Both surfaces — picker and cmdline-completion — consume registrations through the registry.

Two lifecycles (cross-check § “Two registration lifecycles”):

• Persistent: registered at boot via CompletionRegistry::register_source, lives until shutdown. First-party Files / Buffers / Commands etc. Plugin sources whose data is synchronously enumerable.

• Transient: constructed per-use by the host (LSP pickers building from async responses) or a plugin (async- fetch), passed directly to Picker::open_with(reg), dropped after accept/dismiss. Same shape; just shorter lifetime.

Fields

spec: SourceSpec

kind: CandidateSourceKind

accept: Option<Arc<dyn AcceptHandler>>

Accept handler. None ⇒ candidate selection is effectively a no-op (rare; cmdline-completion sources today don’t carry an explicit handler — the accept logic is inline. Slice 7c migrates those to explicit handlers returning AcceptAction::InsertText).

matcher_override: Option<MatcherId>

Per-source matcher override. None ⇒ use the registry default.

ranker_overrides: Vec<RankerId>

Per-source ranker chain override. Empty ⇒ use the registry default chain.

annotator_extras: Vec<AnnotatorId>

Additional annotators to run on this source’s candidates, in registration order. Appended to (not replacing) the registry default annotators.