Introduce FetchTask to tie database observation to view lifetime (pointfreeco#295)

* Support tasks for loading query.

* wip

* wip

* new test

* wip

* wip

* wip

* Add @discardableResult to load functions

* Added a migration guide.

---------

Co-authored-by: Brandon Williams <mbrandonw@hey.com>

Author: 2 people

.github/workflows/ci.yml

@@ -14,11 +14,11 @@ jobs:
     name: macOS
     strategy:
       matrix:
-        xcode: ['16.4']
+        xcode: ['26.1']
         config: ['debug', 'release']
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Select Xcode ${{ matrix.xcode }}
         run: sudo xcode-select -s /Applications/Xcode_${{ matrix.xcode }}.app
       - name: Run ${{ matrix.config }} tests
@@ -28,13 +28,13 @@ jobs:
     name: Examples
     strategy:
       matrix:
-        xcode: ['16.4']
+        xcode: ['26.1']
         config: ['debug']
         scheme: ['Reminders', 'CaseStudies', 'SyncUps']
-    runs-on: macos-15
+    runs-on: macos-26
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Select Xcode ${{ matrix.xcode }}
         run: sudo xcode-select -s /Applications/Xcode_${{ matrix.xcode }}.app
       - name: List devices available

Examples/Examples.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -122,7 +122,7 @@ struct ReminderFormView: View {
         }
         .task(id: reminder.remindersListID) {
           await withErrorReporting {
-            try await $remindersList.load(RemindersList.find(reminder.remindersListID))
+            try await $remindersList.load(RemindersList.find(reminder.remindersListID)).task
           }
         }
       }

Examples/Reminders/ReminderForm.swift

@@ -387,8 +387,14 @@ nonisolated private let logger = Logger(subsystem: "Reminders", category: "Datab
     func seedSampleData() throws {
       @Dependency(\.date.now) var now
       @Dependency(\.uuid) var uuid
-      let remindersListIDs = (0...2).map { _ in uuid() }
-      let reminderIDs = (0...10).map { _ in uuid() }
+      var remindersListIDs: [UUID] = []
+      for _ in 0...2 {
+        remindersListIDs.append(uuid())
+      }
+      var reminderIDs: [UUID] = []
+      for _ in 0...10 {
+        reminderIDs.append(uuid())
+      }
       try seed {
         RemindersList(
           id: remindersListIDs[0],

Examples/Reminders/Schema.swift

@@ -53,7 +53,7 @@ let package = Package(
     .package(url: "https://github.com/pointfreeco/swift-concurrency-extras", from: "1.3.0"),
     .package(url: "https://github.com/pointfreeco/swift-custom-dump", from: "1.3.3"),
     .package(url: "https://github.com/pointfreeco/swift-dependencies", from: "1.9.0"),
-    .package(url: "https://github.com/pointfreeco/swift-perception", "1.4.1"..<"3.0.0"),
+    .package(url: "https://github.com/pointfreeco/swift-perception", from: "2.0.0"),
     .package(
       url: "https://github.com/bok-/swift-sharing-with-traits",
       from: "2.7.4+traits",

Package.swift

@@ -0,0 +1,17 @@
+# Migration guides
+
+Learn how to upgrade your application to the latest version of SQLiteData.
+
+## Overview
+
+SQLiteData is under constant development, and we are always looking for ways to simplify the
+library and make it more powerful. As such, we often need to deprecate certain APIs in favor of
+newer ones. We recommend people update their code as quickly as possible to the newest APIs, and
+these guides contain tips to do so.
+
+> Important: Before following any particular migration guide be sure you have followed all the
+> preceding migration guides.
+
+## Topics
+
+- <doc:MigratingTo1.4>

Sources/SQLiteData/Documentation.docc/Articles/MigrationGuides.md

@@ -0,0 +1,36 @@
+# Migrating to 1.4
+
+SQLiteData 1.4 introduces a new tool for tying the lifecycle database subscriptions to the
+lifecycle of the surrounding async context, but it may incidentally cause "Result of call … 
+is unused" warnings in your project.
+
+## Overview
+
+The `load` method defined on [`@FetchAll`](<doc:FetchAll>) / [`@FetchOne`](<doc:FetchOne>) /
+[`@Fetch`](<doc:Fetch>) all now return a discardable result, ``FetchSubscription``. Awaiting the
+``FetchSubscription/task`` of that result ties the lifecycle of the subscription to the database
+to the lifecycle of the surrounding async context, which can help views to automatically 
+unsubscribe from the database when they are not visible.
+
+However, when used with `withErrorReporting` you are likely to get the following warning:
+
+```swift
+private func updateQuery() async {
+  // ⚠️ Result of call to 'withErrorReporting(_:to:fileID:filePath:line:column:isolation:catching:)' is unused
+  await withErrorReporting {
+    try await $rows.load(…)
+  }
+}
+```
+
+This is happening because although `load` has a discardable result, Swift does not propagate that
+to `withErrorReporting`, and so Swift thinks you have an unused value. To fix you will need to
+explicitly ignore the result with `_ = `:
+
+```swift
+private func updateQuery() async {
+  _ = await withErrorReporting {
+    try await $rows.load(…)
+  }
+}
+```

Sources/SQLiteData/Documentation.docc/Articles/MigrationGuides/MigratingTo1.4.md

@@ -309,6 +309,7 @@ with SQLite to take full advantage of GRDB and SQLiteData.
 - ``FetchAll``
 - ``FetchOne``
 - ``Fetch``
+- ``FetchSubscription``
 
 ### CloudKit synchronization and sharing
 

Sources/SQLiteData/Documentation.docc/SQLiteData.md

@@ -139,11 +139,14 @@ public struct Fetch<Value: Sendable>: Sendable {
   ///   - request: A request describing the data to fetch.
   ///   - database: The database to read from. A value of `nil` will use the default database
   ///     (`@Dependency(\.defaultDatabase)`).
+  /// - Returns: A subscription associated with the observation.
+  @discardableResult
   public func load(
     _ request: some FetchKeyRequest<Value>,
     database: (any DatabaseReader)? = nil
-  ) async throws {
+  ) async throws -> FetchSubscription {
     try await sharedReader.load(.fetch(request, database: databaseOrDefault(database)))
+    return FetchSubscription(sharedReader: sharedReader)
   }
 }
 
@@ -183,13 +186,15 @@ extension Fetch {
   ///     (`@Dependency(\.defaultDatabase)`).
   ///   - scheduler: The scheduler to observe from. By default, database observation is performed
   ///     asynchronously on the main queue.
+  /// - Returns: A subscription associated with the observation.
+  @discardableResult
   public func load(
     _ request: some FetchKeyRequest<Value>,
     database: (any DatabaseReader)? = nil,
     scheduler: some ValueObservationScheduler & Hashable
-  ) async throws {
-    try await sharedReader.load(
-      .fetch(request, database: databaseOrDefault(database), scheduler: scheduler))
+  ) async throws -> FetchSubscription {
+    try await sharedReader.load(.fetch(request, database: databaseOrDefault(database), scheduler: scheduler))
+    return FetchSubscription(sharedReader: sharedReader)
   }
 }
 
@@ -271,14 +276,16 @@ extension Fetch: Equatable where Value: Equatable {
     ///     (`@Dependency(\.defaultDatabase)`).
     ///   - animation: The animation to use for user interface changes that result from changes to
     ///     the fetched results.
+    /// - Returns: A subscription associated with the observation.
     @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
+    @discardableResult
     public func load(
       _ request: some FetchKeyRequest<Value>,
       database: (any DatabaseReader)? = nil,
       animation: Animation
-    ) async throws {
-      try await sharedReader.load(
-        .fetch(request, database: databaseOrDefault(database), animation: animation))
+    ) async throws -> FetchSubscription {
+      try await sharedReader.load(.fetch(request, database: databaseOrDefault(database), animation: animation))
+      return FetchSubscription(sharedReader: sharedReader)
     }
   }
 #endif