Extract generated code to method

drift/lib/src/runtime/query_builder/schema/column_impl.dart

@@ -246,6 +246,34 @@ class GeneratedColumn<T extends Object> extends Column<T> {
       return const VerificationResult.success();
     };
   }
+
+  /// A helper method to make creating [defaultConstraints] simpler. Used when
+  /// the constraint does not depend on the dialect.
+  ///
+  /// Used by generated code.
+  static Function(GenerationContext) constraintIsAlways(String constraint) =>
+      (context) => context.buffer
+        ..write(' ')
+        ..write(constraint);
+
+  /// A helper method to make creating [defaultConstraints] simpler. Used when
+  /// the constraint depends on the dialect.
+  ///
+  /// Used by generated code.
+  static Function(GenerationContext) constraintsDependsOnDialect(
+    Map<SqlDialect, String> constraints,
+  ) =>
+      (context) {
+        final constraint = constraints[context.dialect];
+
+        if (constraint == null || constraint.isEmpty) {
+          return;
+        }
+
+        context.buffer
+          ..write(' ')
+          ..write(constraint);
+      };
 }
 
 /// A [GeneratedColumn] with a type converter attached to it.

drift_dev/lib/src/writer/tables/table_writer.dart

@@ -53,23 +53,28 @@ abstract class TableOrViewWriter {
     } else if (constraints.values.any((constraint) => constraint.isNotEmpty)) {
       // Use the default constraints supported by drift
 
-      final literalEntries = [
-        for (final entry in constraints.entries)
-          'SqlDialect.${entry.key.name}: ${asDartLiteral(entry.value)},',
-      ];
+      if (constraints.values.any(
+        (value) => value != constraints.values.first,
+      )) {
+        // One or more constraints are different depending on dialect, generate
+        // per-dialect constraints
 
-      additionalParams['defaultConstraints'] = '''(context) {
-        const dialectConstraints = {
-          ${literalEntries.join('\n')}
-        };
+        final literalEntries = [
+          for (final entry in constraints.entries)
+            'SqlDialect.${entry.key.name}: ${asDartLiteral(entry.value)},',
+        ];
 
-        final constraints = dialectConstraints[context.dialect]!;
-        if (constraints.isEmpty) {
-          return;
-        }
+        additionalParams['defaultConstraints'] =
+            'GeneratedColumn.constraintsDependsOnDialect({${literalEntries.join('\n')}})';
+      } else {
+        // Constraints are the same regardless of dialect, only generate one set
+        // of them
 
-        context.buffer..write(' ')..write(constraints);
-      }''';
+        final constraint = asDartLiteral(constraints.values.first);
+
+        additionalParams['defaultConstraints'] =
+            'GeneratedColumn.constraintIsAlways($constraint)';
+      }
     }
 
     if (column.defaultArgument != null) {