⚡ Bolt: Optimize ViewModel array allocations

.jules/bolt.md

@@ -28,3 +28,6 @@
 ## 2025-10-24 - Bulk Disk I/O Parallelization and Thread Pool Starvation
 **Learning:** Both `withTaskGroup` and `Task.detached` schedule their work on Swift's cooperative thread pool, which has only as many threads as the CPU has cores. Running synchronous blocking I/O (like `FileManager.removeItem`) directly inside such tasks ties up cooperative threads — when every thread is parked in a syscall there is nothing left to advance other Swift Concurrency work, which manifests as starvation and (with self-referential `await` chains) outright deadlock. `Task.detached` does not help here: "detached" means unstructured/independent, not "off the cooperative pool."
 **Action:** To parallelize bulk blocking I/O, combine a sliding-window `withThrowingTaskGroup` (e.g., `maxConcurrency` of 8) with a per-item handoff to a GCD queue: wrap the blocking call in `withCheckedThrowingContinuation` and dispatch it via `DispatchQueue.global(qos: .userInitiated).async { ... continuation.resume(...) }`. The cooperative-pool task only `await`s the continuation, so it never holds a thread while the syscall runs.
+## 2024-05-30 - Short-circuiting Computed Property Evaluations in SwiftUI
+**Learning:** In SwiftUI, computed properties on `@Observable` or `ObservableObject` view models are often re-evaluated on every render cycle (e.g., when bound to `.disabled()`). Using `.filter { ... }.isEmpty` inside these properties eagerly allocates a new array and takes O(N) time on every render frame.
+**Action:** Always use `.contains(where:)` instead of `.filter { ... }.isEmpty` to short-circuit the evaluation, enabling O(1) best-case performance and eliminating memory churn.

Sources/Cacheout/ViewModels/CacheoutViewModel.swift

@@ -106,7 +106,8 @@ class CacheoutViewModel: ObservableObject {
     }
 
     var selectedSize: Int64 {
-        selectedResults.reduce(0) { $0 + $1.sizeBytes }
+        // ⚡ Bolt: Use lazy filter to prevent intermediate array allocation during size reduction
+        scanResults.lazy.filter(\.isSelected).reduce(0) { $0 + $1.sizeBytes }
     }
 
     var formattedSelectedSize: String {
@@ -118,7 +119,10 @@ class CacheoutViewModel: ObservableObject {
     }
 
     var hasResults: Bool { !scanResults.isEmpty || !nodeModulesItems.isEmpty }
-    var hasSelection: Bool { !selectedResults.isEmpty || selectedNodeModulesSize > 0 }
+    var hasSelection: Bool {
+        // ⚡ Bolt: Short-circuit evaluation instead of eagerly filtering the entire array
+        scanResults.contains(where: \.isSelected) || selectedNodeModulesSize > 0
+    }
 
     // MARK: - Node Modules computed properties