Fix SwiftUI update loop caused by auto-refresh timer teardown

.github/workflows/build_and_test.yml

@@ -48,7 +48,8 @@ jobs:
           xcodebuild -resolvePackageDependencies -workspace swiftchan.xcodeproj/project.xcworkspace -scheme swiftchan -clonedSourcePackagesDirPath build/SourcePackages -onlyUsePackageVersionsFromResolvedFile
 
       - name: Build and test
-        run: bundle exec fastlane tests
+        timeout-minutes: 20
+        run: bash ci_scripts/test_with_diagnostics.sh
 
       - name: Upload test results
         if: always()

ci_scripts/test_with_diagnostics.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+set -euo pipefail
+
+# XCTest's timeout often omits the app's blocked stack. Capture it while the app is alive.
+bundle exec fastlane tests &
+test_pid=$!
+(
+  while kill -0 "$test_pid" 2>/dev/null; do
+    sleep 60
+    for app_pid in $(pgrep -x swiftchan || true); do
+      output_dir="fastlane/test_output/main-thread-samples"
+      mkdir -p "$output_dir"
+      sample "$app_pid" 1 -file "$output_dir/$app_pid-$(date +%s).txt" >/dev/null 2>&1 || true
+    done
+  done
+) &
+monitor_pid=$!
+trap 'kill "$monitor_pid" 2>/dev/null || true' EXIT
+wait "$test_pid"

swiftchan/Views/Boards/Catalog/Thread/ThreadAutoRefresher.swift

@@ -5,22 +5,23 @@ import Combine
 class ThreadAutoRefresher {
     private(set) var secondsRemaining: Int = 0
     var pauseAutoRefresh: Bool = false
-    var isActive: Bool = true
+    var isActive: Bool = false
 
-    private var timerCancellable: AnyCancellable?
-    private var cachedRefreshEnabled: Bool = false
-    private var cachedRefreshTime: Int = 10
+    @ObservationIgnored private var timerCancellable: AnyCancellable?
+    @ObservationIgnored private var cachedRefreshEnabled: Bool = false
+    @ObservationIgnored private var cachedRefreshTime: Int = 10
 
-    var onRefresh: (() -> Void)?
+    @ObservationIgnored var onRefresh: (() -> Void)?
 
     init() {
         updateCachedSettings()
         resetTimer()
-        startTimer()
     }
 
     deinit {
-        cancelTimer()
+        // SwiftUI discards temporary State initial values during body evaluation.
+        // Deinitialization must not invalidate that evaluation through Observation.
+        timerCancellable?.cancel()
     }
 
     func updateCachedSettings() {

swiftchanTests/ThreadViewModelTests.swift

@@ -1,9 +1,24 @@
 import XCTest
 import FourChan
+import Observation
 @testable import swiftchan
 
 @MainActor
 final class ThreadViewModelTests: XCTestCase {
+    func testDiscardingTemporaryRefresherDoesNotInvalidatePresentingView() {
+        let invalidation = expectation(description: "Temporary timer does not invalidate view construction")
+        invalidation.isInverted = true
+        var refresher: ThreadAutoRefresher? = withObservationTracking {
+            ThreadAutoRefresher()
+        } onChange: {
+            invalidation.fulfill()
+        }
+        XCTAssertNotNil(refresher)
+        XCTAssertFalse(refresher?.isActive ?? true)
+        refresher = nil
+        wait(for: [invalidation], timeout: 0.05)
+    }
+
     func testSharedPostLinkPreservesBoardThreadAndExactReply() {
         let model = ThreadViewModel(boardName: "biz", id: 100)
         XCTAssertEqual(model.postURL(105).absoluteString, "https://boards.4chan.org/biz/thread/100#p105")