refactor: split WorldEvent into EntityEvent and RelEvent

src/index.ts

@@ -11,6 +11,8 @@ export { makeEntity, entityIndex, entityGeneration } from "./entity";
 export { SparseSet } from "./storage/sparse-set";
 export type {
   WorldEvent,
+  EntityEvent,
+  RelEvent,
   QueryUpdate,
   RelationshipUpdate,
 } from "./observable/events";

src/observable/events.ts

@@ -4,17 +4,25 @@ import type { Entity } from "../entity";
 
 // ── World Events ──────────────────────────────────────
 /**
- * Discriminated union of all world-level events.
- * Emitted via `world.events$`.
+ * Events that carry an `entity` field — component and lifecycle events.
  */
-export type WorldEvent =
+export type EntityEvent =
   | SpawnedEvent
   | DestroyedEvent
   | ComponentAddedEvent
   | ComponentRemovedEvent
-  | ComponentChangedEvent
-  | RelAddedEvent
-  | RelRemovedEvent;
+  | ComponentChangedEvent;
+
+/**
+ * Events that carry `source`/`target` fields — relationship events.
+ */
+export type RelEvent = RelAddedEvent | RelRemovedEvent;
+
+/**
+ * Discriminated union of all world-level events.
+ * Emitted via `world.events$`.
+ */
+export type WorldEvent = EntityEvent | RelEvent;
 
 export interface SpawnedEvent {
   type: "spawned";

src/observable/observe.ts

@@ -1,7 +1,12 @@
 import { Subject } from "rxjs";
 import type { Query } from "../query";
 import type { Entity } from "../entity";
-import type { WorldEvent, QueryUpdate, RelationshipUpdate } from "./events";
+import type {
+  WorldEvent,
+  EntityEvent,
+  QueryUpdate,
+  RelationshipUpdate,
+} from "./events";
 import type { RelationshipDef } from "../relationship";
 import type { ComponentDef } from "../component";
 
@@ -143,21 +148,21 @@ export class ObservableLayer {
     queryMatches: (query: Query, e: Entity) => boolean,
   ): void {
     if (!("entity" in event)) return;
+    const entityEvent = event as EntityEvent;
 
     // Determine which component keys are relevant
     let keys: symbol[] = [];
 
-    switch (event.type) {
+    switch (entityEvent.type) {
       case "spawned":
       case "destroyed":
-        // Check all observers (via the ANY_KEY set)
         keys = [ANY_KEY];
         break;
 
       case "componentAdded":
       case "componentRemoved":
       case "componentChanged":
-        keys = [event.component._key];
+        keys = [entityEvent.component._key];
         break;
     }
 
@@ -169,7 +174,8 @@ export class ObservableLayer {
       for (const o of set) {
         if (!seen.has(o)) {
           seen.add(o);
-          this._updateObserver(o, event, queryMatches);
+          // event is entity-bearing after the in-guard above
+          this._updateObserver(o, entityEvent, queryMatches);
         }
       }
     }
@@ -179,10 +185,10 @@ export class ObservableLayer {
 
   private _updateObserver(
     obs: QueryObserverState,
-    event: WorldEvent,
+    event: EntityEvent,
     queryMatches: (query: Query, e: Entity) => boolean,
   ): void {
-    const e = event.entity!;
+    const e = event.entity;
     const wasMatched = obs.matched.has(e);
     const nowMatches = queryMatches(obs.query, e);