Detect SyncEngine.isSynchronizing misuse in triggers

A warning is raised to suggest `$isSynchronizing`, instead.

Author: stephencelis

Package.resolved

@@ -37,7 +37,8 @@ let package = Package(
     .package(url: "https://github.com/pointfreeco/swift-snapshot-testing", from: "1.18.4"),
     .package(
       url: "https://github.com/pointfreeco/swift-structured-queries",
-      from: "0.27.0",
+      branch: "trigger-local",
+      // from: "0.27.0",
       traits: [
         .trait(name: "StructuredQueriesTagged", condition: .when(traits: ["SQLiteDataTagged"]))
       ]

Package.swift

@@ -899,7 +899,15 @@
     /// See <doc:CloudKit#Updating-triggers-to-be-compatible-with-synchronization> for more info.
     @DatabaseFunction("sqlitedata_icloud_syncEngineIsSynchronizingChanges")
     public static var isSynchronizing: Bool {
-      _isSynchronizingChanges
+      if _isCreatingTemporaryTrigger {
+        reportIssue(
+          """
+          Invoked 'SyncEngine.isSynchronizing' at trigger creation, which is unexpected. Use \
+          'SyncEngine.$isSynchronizing' to invoke at trigger execution, instead.
+          """
+        )
+      }
+      return _isSynchronizingChanges
     }
 
     @available(*, deprecated, message: "Use 'SyncEngine.$isSynchronizing', instead.")

Sources/SQLiteData/CloudKit/SyncEngine.swift

@@ -93,6 +93,28 @@
             """
         )
       }
+
+      @Test func isSynchronizingTriggerWarning() {
+        withKnownIssue {
+          _ = Reminder.createTemporaryTrigger(
+            after: .insert { new in
+              Values(SyncEngine.isSynchronizing)
+            }
+          )
+        } matching: { issue in
+          issue.description.hasSuffix(
+            """
+            Invoked 'SyncEngine.isSynchronizing' at trigger creation, which is unexpected. Use \
+            'SyncEngine.$isSynchronizing' to invoke at trigger execution, instead.
+            """
+          )
+        }
+        _ = Reminder.createTemporaryTrigger(
+          after: .insert { new in
+            Values(SyncEngine.$isSynchronizing)
+          }
+        )
+      }
     }
   }