Return value from callable to work around VM issue

Due to dart-lang/sdk#56064, Dart stable 3.4
reports an exception on native calls involving `NativeCallable`s
returning `null` (which they do for `void`).
This exception is not critical as it only occurs when a debugger is
attached, but it's still annoying and easy to work around by returning
a bogus value then dropped.

Closes simolus3#242

Author: simolus3

sqlite3/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.4.4
+
+- Add a temporary workaround for [a Dart bug](https://github.com/dart-lang/sdk/issues/56064)
+  causing spurious exceptions when databases are closed and a debugger is attached.
+
 ## 2.4.3
 
 - Migrate away from legacy web APIs: `dart:html`, `dart:js`, `dart:indexeddb`

sqlite3/lib/src/ffi/bindings.dart

@@ -299,10 +299,13 @@ final class FfiDatabase extends RawSqliteDatabase {
 
   static Pointer<NativeFunction<Void Function(Pointer<Void>)>> _xDestroy(
       List<NativeCallable> callables) {
-    void destroy(Pointer<Void> _) {
+    int destroy(Pointer<Void> _) {
       for (final callable in callables) {
         callable.close();
       }
+
+      // TODO: Remove and change to void after Dart 3.5 or https://github.com/dart-lang/sdk/issues/56064
+      return 0;
     }
 
     final callable =
@@ -711,7 +714,9 @@ extension on RawXFunc {
   NativeCallable<_XFunc> toNative(Bindings bindings) {
     return NativeCallable.isolateLocal((Pointer<sqlite3_context> ctx, int nArgs,
         Pointer<Pointer<sqlite3_value>> args) {
-      return this(FfiContext(bindings, ctx), _ValueList(nArgs, args, bindings));
+      this(FfiContext(bindings, ctx), _ValueList(nArgs, args, bindings));
+      // TODO: Remove and change to void after Dart 3.5 or https://github.com/dart-lang/sdk/issues/56064
+      return 0;
     })
       ..keepIsolateAlive = false;
   }
@@ -721,9 +726,10 @@ extension on RawXFinal {
   NativeCallable<_XFinal> toNative(Bindings bindings, bool clean) {
     return NativeCallable.isolateLocal((Pointer<sqlite3_context> ctx) {
       final context = FfiContext(bindings, ctx);
-      final res = this(context);
+      this(context);
       if (clean) context.freeContext();
-      return res;
+      // TODO: Remove and change to void after Dart 3.5 or https://github.com/dart-lang/sdk/issues/56064
+      return 0;
     })
       ..keepIsolateAlive = false;
   }
@@ -757,12 +763,9 @@ extension on RawUpdateHook {
         final tableName = table.readString();
         this(kind, tableName, rowid);
 
-        // This closure needs to return `void` exactly to make the FFI analyzer
-        // happy.
-        return _returnsVoid();
+        // TODO: Remove and change to void after Dart 3.5 or https://github.com/dart-lang/sdk/issues/56064
+        return 0;
       },
     )..keepIsolateAlive = false;
   }
-
-  static void _returnsVoid() {}
 }

sqlite3/pubspec.yaml

@@ -1,6 +1,6 @@
 name: sqlite3
 description: Provides lightweight yet convenient bindings to SQLite by using dart:ffi
-version: 2.4.3
+version: 2.4.4
 homepage: https://github.com/simolus3/sqlite3.dart/tree/main/sqlite3
 issue_tracker: https://github.com/simolus3/sqlite3.dart/issues