fix: iterator uniqueness

.changeset/silent-peas-fold.md

@@ -0,0 +1,5 @@
+---
+"alcaeus": patch
+---
+
+Iterating response would return same resource multiple times

src/ResourceRepresentation.ts

@@ -6,6 +6,8 @@ import type { ResourceFactory } from '@tpluscode/rdfine/lib/ResourceFactory'
 import type { RdfResourceCore } from '@tpluscode/rdfine/RdfResource'
 import type { AnyContext, AnyPointer, GraphPointer } from 'clownface'
 import type { DatasetCore, NamedNode } from 'rdf-js'
+import TermMap from '@rdf-esm/term-map'
+import { Term } from '@rdfjs/types'
 
 export interface ResourceRepresentation<D extends DatasetCore = DatasetCore, T extends RdfResourceCore<D> = Hydra.Resource<D>> extends Iterable<Hydra.Resource<D>> {
     /**
@@ -72,8 +74,15 @@ export default class <D extends DatasetCore, T extends RdfResourceCore<D>> imple
     }
 
     public [Symbol.iterator]() {
-        return this.__graph.in()
-            .map(this._createEntity.bind(this))[Symbol.iterator]()
+        return this.__graph.in().toArray()
+            .reduce((uniq, pointer) => {
+                if (!uniq.has(pointer.term)) {
+                    return uniq.set(pointer.term, this._createEntity(pointer))
+                }
+
+                return uniq
+            }, new TermMap<Term, Hydra.Resource<D>>())
+            .values()
     }
 
     private _createEntity<T>(node: GraphPointer<ResourceIdentifier>) {

tests/ResourceRepresentation-spec.ts

@@ -28,6 +28,27 @@ describe('ResourceRepresentation', () => {
         expect(array.map(r => r.id.value).join()).toBe('http://example.com/a,http://example.com/b,http://example.com/c,http://example.com/d')
     })
 
+    it('should iterate unique resources', () => {
+        // given
+        const dataset = $rdf.dataset()
+        cf({ dataset, graph: ex.a })
+            .namedNode(ex.a).addOut(rdf.type, ex.Res).addOut(schema.knows, [ex.b, ex.c, ex.d])
+            .namedNode(ex.c).addOut(schema.knows, [ex.a, ex.d])
+            .namedNode(ex.d).addIn(schema.knows, ex.a)
+        const r12n = new ResourceRepresentation(cf({ dataset, graph: ex.a }), factory, ex.a)
+
+        // when
+        const array = Array.from(r12n).map(r => r.id)
+
+        // then
+        expect(array).toHaveLength(2)
+        expect(array).toStrictEqual(
+            expect.arrayContaining([
+                ex.a, ex.c,
+            ]),
+        )
+    })
+
     describe('root', () => {
         it('should use selection root resource as specified by parameter', () => {
             // given