⚡ Bolt: Prevent intermediate array allocations in SwiftUI views

.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.
+## 2026-04-05 - Lazy Filter Chains in SwiftUI Computed Properties
+**Learning:** Eager `.filter` operations in SwiftUI computed properties execute on every view re-render, allocating temporary intermediate arrays that cause unnecessary memory churn.
+**Action:** Chain `.lazy.filter` before terminal operations like `.count` or `.sorted()` in UI components to avoid intermediate array allocations during rapid state updates.

Sources/Cacheout/Views/CleanConfirmation.swift

@@ -36,7 +36,8 @@ struct CleanConfirmationSheet: View {
             Text("Clean Selected Caches?")
                 .font(.title2.bold())
 
-            Text("This will remove \(viewModel.formattedTotalSelectedSize) from \(viewModel.selectedResults.count + viewModel.nodeModulesItems.filter(\.isSelected).count) items.")
+            // PERF: Use .lazy.filter before .count to prevent intermediate array allocation
+            Text("This will remove \(viewModel.formattedTotalSelectedSize) from \(viewModel.selectedResults.count + viewModel.nodeModulesItems.lazy.filter(\.isSelected).count) items.")
                 .font(.body)
                 .foregroundStyle(.secondary)
                 .multilineTextAlignment(.center)

Sources/Cacheout/Views/MenuBarView.swift

@@ -154,7 +154,8 @@ struct MenuBarView: View {
             Spacer()
             statPill(
                 label: "Categories",
-                value: "\(viewModel.scanResults.filter { !$0.isEmpty }.count)",
+                // PERF: Use .lazy.filter before .count to prevent intermediate array allocation
+                value: "\(viewModel.scanResults.lazy.filter { !$0.isEmpty }.count)",
                 color: .blue
             )
         }
@@ -177,7 +178,9 @@ struct MenuBarView: View {
     // MARK: - Top Categories
 
     private var topCategories: some View {
+        // PERF: Chain .lazy.filter before .sorted() to prevent intermediate array allocation
         let top = viewModel.scanResults
+            .lazy
             .filter { !$0.isEmpty }
             .sorted { $0.sizeBytes > $1.sizeBytes }
             .prefix(5)