⚡ Bolt: Optimize array filtering and short-circuiting for UI state

.jules/bolt.md

@@ -28,3 +28,6 @@
 ## 2025-10-24 - Bulk Disk I/O Parallelization and Thread Pool Deadlocks
 **Learning:** Attempting to parallelize synchronous bulk I/O operations (like `FileManager.removeItem` loops) using just `TaskGroup` or `Task.detached` can exhaust the Swift cooperative thread pool and cause deadlocks, because `Task.detached` does NOT escape the thread pool.
 **Action:** To optimize bulk I/O operations, parallelize them using `withThrowingTaskGroup` combined with a sliding window iterator (e.g., `maxConcurrency` of 8). Wrap synchronous blocking calls in `withCheckedThrowingContinuation` and explicitly dispatch them to a background GCD queue (e.g., `DispatchQueue.global(qos: .userInitiated).async`) to prevent thread pool starvation.
+## 2024-05-24 - Array Allocation and Short-Circuiting in SwiftUI
+**Learning:** Checking `.isEmpty` on a computed property that wraps an eager `.filter` causes an unnecessary O(N) allocation. Eager `.filter` followed by `.reduce` also forces intermediate memory allocation, which is particularly expensive for computed properties used in SwiftUI views.
+**Action:** Always use `.contains(where:)` to short-circuit existence checks, and chain `.lazy.filter` before `.reduce` to iterate over elements without allocating temporary arrays.

Sources/Cacheout/ViewModels/CacheoutViewModel.swift

@@ -105,8 +105,9 @@ class CacheoutViewModel: ObservableObject {
         scanResults.filter { $0.isSelected }
     }
 
+    // ⚡ Bolt Optimization: Chained .lazy.filter before .reduce to avoid unnecessary O(n) intermediate array allocations. Expected impact: Reduces memory churn during UI updates.
     var selectedSize: Int64 {
-        selectedResults.reduce(0) { $0 + $1.sizeBytes }
+        scanResults.lazy.filter(\.isSelected).reduce(0) { $0 + $1.sizeBytes }
     }
 
     var formattedSelectedSize: String {
@@ -118,7 +119,8 @@ class CacheoutViewModel: ObservableObject {
     }
 
     var hasResults: Bool { !scanResults.isEmpty || !nodeModulesItems.isEmpty }
-    var hasSelection: Bool { !selectedResults.isEmpty || selectedNodeModulesSize > 0 }
+    // ⚡ Bolt Optimization: Use .contains(where:) instead of checking .isEmpty on a filtered array to short-circuit evaluation. Expected impact: O(1) best-case execution instead of O(n) filtering.
+    var hasSelection: Bool { scanResults.contains(where: \.isSelected) || selectedNodeModulesSize > 0 }
 
     // MARK: - Node Modules computed properties