Module subsystem 

crate::diff::subsystem — the moved lattice_diff::subsystem surface PLUS the host-owned BufferRegistry-backed resolver impls, so every crate::diff::subsystem::* call site (including BufferRegistryTextProvider / BufferRegistryDocumentResolver) resolves unchanged after the DX.6 move.

Re-exports

pub use crate::diff::resolver::BufferRegistryDocumentResolver;

pub use crate::diff::resolver::BufferRegistryTextProvider;

Structs

BufferSource

D.8.b (2026-05-31): live-rope participant backed by a buffer. Replaces the prior BufferSource + BufferSource two-struct split (both had identical shape — provider + buffer_id — and only differed in which trait they implemented). The trait collapse to DiffParticipantSource makes the split structurally redundant.

Debouncer

Per-session debounce controller.

DiffDescriptor

The “what to diff against what” pair for a session.

DiffGetPlan

D.5.b (2026-05-30): describes the edit the diff-mode do (diff-get) operator would apply when invoked at a given cursor row on the active side of a session. Produced by DiffSubsystem::compute_get_edit; consumed by dispatch which translates it into an apply_edit_blocking call and re-positions the cursor.

DiffSession

Per-document diff state. Wraps an ArcSwap<HunkIndex> so consumers read the latest published hunks without holding the registry lock.

DiffSessionDescription

One row of :describe-diff output. Produced by DiffSubsystem::describe_sessions and rendered into the help-buffer body by DiffSubsystem::build_describe_diff_content.

DiffSubscriptionGuard

RAII guard returned by DiffSubsystem::bind. Holds the bus SubscriptionId + the drainer task JoinHandle. On Drop, unsubscribes the bus subscription and aborts the drainer task.

DiffSubsystem

Process-wide registry + routing layer for diff sessions.

OnDiskSource

D.3.a (2026-05-29): on-disk file participant source.

StaticSource

In-memory participant source — an owned Rope cloned on every Self::snapshot.

Enums

DiffGetOutcome

D.6.d (2026-05-31): outcome of resolving the diff-mode do chord or :diffget [<bufnr>] ex-command. Mirrors DiffPutOutcome’s tri-state but for the get direction:

DiffOutcome

D.6.e (2026-05-31): resolution signal fired through a DiffSession’s completion channel when the user invokes :diff-accept / :diff-reject. Consumed by the future openDiff plugin flow (Claude Code, AI multi-file edits) and by any in-tree consumer (magit plugin, AI proposals) that wants to know how the user resolved a session.

DiffPutOutcome

D.5.c (2026-05-30) / D.6.d (2026-05-31): outcome of resolving the diff-mode dp chord or :diffput [<bufnr>] ex-command. Distinguishes four cases the dispatch handler must surface differently:

MembershipError

D.8.d (2026-05-31): errors the subsystem’s membership API returns when mutating a session’s participant set. Distinct from [DiffEngineError] (which is the engine crate’s surface) so callers don’t have to import lattice_diff just to pattern-match on add_participant failures. The engine’s cap on arity (N ≥ 4 rejected in v1) surfaces here as EngineRejected(DiffEngineError::Unsupported{...}).

Constants

DEFAULT_DEBOUNCE_WINDOW

Default debounce window. Matches Helix’s diff debounce (50ms); short enough that the visual lag is imperceptible during sustained typing, long enough that a burst of 5–10 keystrokes collapses to a single recompute. Overridable via DiffSubsystem::with_debounce_window for tests and host configuration.

Traits

BufferTextProvider

One-trait seam between the diff subsystem and the host’s buffer storage. Required for BufferSource to resolve a BufferId to its live rope at snapshot time.

DiffParticipantSource

One participant in a diff session — produces the rope to diff for one slot in Hunk::ranges.

DocumentBufferResolver

Translates the protocol-layer DocumentId carried in Event::DocumentChanged / Event::DocumentClosed back to a host-layer BufferId. The host supplies an impl backed by BufferRegistry. Kept as a trait so the subsystem stays independent of buffer-registry layout (and so tests can inject a stub mapping).

Type Aliases

DiffSubsystemHandle

Cheap-clone service handle for the diff subsystem. DX.3/C7 (BC.6): registered in the ServiceRegistry at boot so diff-mode’s on_activate can reach the session for a buffer (ctx.service::<DiffSubsystemHandle>()) and register a HunkFoldSource via the FoldOverlayService — mirroring how MultibufferMode reaches its MultibufferRegistryHandle. Follows the Arc/TypeId convention: register Arc<DiffSubsystem>, look up Arc<DiffSubsystem>.