Fix nested tag reference merging

Author: tomasf

Sources/Cadova/Abstract Layer/Environment/Values/Environment+Anchors.swift

@@ -17,9 +17,15 @@ internal extension EnvironmentValues {
     }
 
     func withDefinedReferences(_ referenceState: ReferenceState) -> Self {
-        setting(key: Self.environmentKey, value: UpstreamReferences(
-            anchors: referenceState.definedAnchors,
-            tags: referenceState.definedTags
+        let existingReferences = upstreamReferences
+        let mergedAnchors = (existingReferences?.anchors ?? [:])
+            .merging(referenceState.definedAnchors) { $0.union($1) }
+        let mergedTags = (existingReferences?.tags ?? [:])
+            .merging(referenceState.definedTags) { $0 + $1 }
+
+        return setting(key: Self.environmentKey, value: UpstreamReferences(
+            anchors: mergedAnchors,
+            tags: mergedTags
         ))
     }
 

Tests/Tests/Tags.swift

@@ -34,4 +34,27 @@ struct TagTests {
         #expect(try await geometry.bounds ≈ .init(minimum: [-5, -5, 0], maximum: [5, 5, 17]))
         #expect(try await geometry.measurements.volume ≈ 567.631)
     }
+
+    @Test func `tag references include definitions from nested and outer booleans`() async throws {
+        let sharedTag = Tag("shared tag")
+
+        let geometry = Box(x: 21, y: 1, z: 1)
+            .subtracting {
+                sharedTag
+            }
+            .adding {
+                Box(1)
+                    .tagged(sharedTag)
+                    .subtracting { Box(1) }
+                    .translated(x: 5)
+            }
+            .adding {
+                Box(1)
+                    .tagged(sharedTag)
+                    .subtracting { Box(1) }
+                    .translated(x: 15)
+            }
+
+        #expect(try await geometry.measurements.volume ≈ 19)
+    }
 }