Add tests

drift/test/database/expressions/expression_test.dart

@@ -175,4 +175,16 @@ void main() {
       generates('(a OR b) AND c AND d'),
     );
   });
+
+  test('dialect-specific custom expression', () {
+    final expr = CustomExpression.dialectSpecific({
+      SqlDialect.mariadb: 'mariadb',
+      SqlDialect.postgres: 'pg',
+      SqlDialect.sqlite: 'default',
+    });
+
+    expect(expr, generatesWithOptions('mariadb', dialect: SqlDialect.mariadb));
+    expect(expr, generatesWithOptions('pg', dialect: SqlDialect.postgres));
+    expect(expr, generatesWithOptions('default', dialect: SqlDialect.sqlite));
+  });
 }

drift/test/test_utils/matchers.dart

@@ -17,14 +17,25 @@ void expectNotEquals(dynamic a, dynamic expected) {
 /// matching [sql] and, optionally, the matching [variables].
 Matcher generates(dynamic sql, [dynamic variables = isEmpty]) {
   return _GeneratesSqlMatcher(
-      wrapMatcher(sql), wrapMatcher(variables), const DriftDatabaseOptions());
+    wrapMatcher(sql),
+    wrapMatcher(variables),
+    const DriftDatabaseOptions(),
+    SqlDialect.sqlite,
+  );
 }
 
-Matcher generatesWithOptions(dynamic sql,
-    {dynamic variables = isEmpty,
-    DriftDatabaseOptions options = const DriftDatabaseOptions()}) {
+Matcher generatesWithOptions(
+  dynamic sql, {
+  dynamic variables = isEmpty,
+  DriftDatabaseOptions options = const DriftDatabaseOptions(),
+  SqlDialect dialect = SqlDialect.sqlite,
+}) {
   return _GeneratesSqlMatcher(
-      wrapMatcher(sql), wrapMatcher(variables), options);
+    wrapMatcher(sql),
+    wrapMatcher(variables),
+    options,
+    dialect,
+  );
 }
 
 class _GeneratesSqlMatcher extends Matcher {
@@ -32,8 +43,14 @@ class _GeneratesSqlMatcher extends Matcher {
   final Matcher? _matchVariables;
 
   final DriftDatabaseOptions options;
+  final SqlDialect dialect;
 
-  _GeneratesSqlMatcher(this._matchSql, this._matchVariables, this.options);
+  _GeneratesSqlMatcher(
+    this._matchSql,
+    this._matchVariables,
+    this.options,
+    this.dialect,
+  );
 
   @override
   Description describe(Description description) {
@@ -78,7 +95,7 @@ class _GeneratesSqlMatcher extends Matcher {
       return false;
     }
 
-    final ctx = stubContext(options: options);
+    final ctx = stubContext(options: options, dialect: dialect);
     item.writeInto(ctx);
 
     var matches = true;

drift/test/test_utils/test_utils.dart

@@ -43,15 +43,20 @@ DatabaseConnection createConnection(QueryExecutor executor,
       streamQueries: streams ?? StreamQueryStore());
 }
 
-GenerationContext stubContext({DriftDatabaseOptions? options}) {
-  return GenerationContext(
-      options ?? const DriftDatabaseOptions(), _NullDatabase.instance);
+GenerationContext stubContext({
+  DriftDatabaseOptions? options,
+  SqlDialect dialect = SqlDialect.sqlite,
+}) {
+  final warnBefore = driftRuntimeOptions.dontWarnAboutMultipleDatabases;
+  driftRuntimeOptions.dontWarnAboutMultipleDatabases = true;
+  final database = _NullDatabase(_NullExecutor(dialect: dialect));
+  driftRuntimeOptions.dontWarnAboutMultipleDatabases = warnBefore;
+
+  return GenerationContext(options ?? const DriftDatabaseOptions(), database);
 }
 
 class _NullDatabase extends GeneratedDatabase {
-  static final instance = _NullDatabase();
-
-  _NullDatabase() : super(_NullExecutor());
+  _NullDatabase([QueryExecutor? e]) : super(e ?? _NullExecutor());
 
   @override
   Iterable<TableInfo<Table, dynamic>> get allTables =>
@@ -63,7 +68,9 @@ class _NullDatabase extends GeneratedDatabase {
 
 class _NullExecutor extends Fake implements QueryExecutor {
   @override
-  SqlDialect get dialect => SqlDialect.sqlite;
+  final SqlDialect dialect;
+
+  _NullExecutor({this.dialect = SqlDialect.sqlite});
 }
 
 class CustomTable extends Table with TableInfo<CustomTable, void> {