Don't try to fake unfakable classes

We have to rely on runtime dummy value lookup instead.

Also adds a dummy value for SDK's `ProcessResult`, `SplayTreeMap`,
`SplayTreeSet` and `Isolate` classes, which are `final`.

I guess we want to cover all final SDK classes eventually.

Also bump the version used in the generator tests to 3.0.

#dart3

PiperOrigin-RevId: 534338463

Author: Ilya Yanok

lib/src/builder.dart

@@ -124,8 +124,7 @@ class MockBuilder implements Builder {
     // The source lib may be pre-null-safety because of an explicit opt-out
     // (`// @dart=2.9`), as opposed to living in a pre-null-safety package. To
     // allow for this situation, we must also add an opt-out comment here.
-    final dartVersionComment =
-        sourceLibIsNonNullable ? '// @dart=2.19' : '// @dart=2.9';
+    final dartVersionComment = sourceLibIsNonNullable ? '' : '// @dart=2.9';
     final mockLibraryContent = DartFormatter().format('''
 // Mocks generated by Mockito $packageVersion from annotations
 // in ${entryLib.definingCompilationUnit.source.uri.path}.
@@ -1444,6 +1443,11 @@ class _MockClassInfo {
     ]);
   }
 
+  Expression _dummyValueFallbackToRuntime(
+          analyzer.DartType type, Expression invocation) =>
+      referImported('dummyValue', 'package:mockito/src/dummies.dart')
+          .call([refer('this'), invocation], {}, [_typeReference(type)]);
+
   Expression _dummyValue(analyzer.DartType type, Expression invocation) {
     // The type is nullable, just take a shortcut and return `null`.
     if (typeSystem.isNullable(type)) {
@@ -1460,8 +1464,7 @@ class _MockClassInfo {
         return literalNull;
       }
       // As a last resort, try looking for the correct value at run-time.
-      return referImported('dummyValue', 'package:mockito/src/dummies.dart')
-          .call([refer('this'), invocation], {}, [_typeReference(type)]);
+      return _dummyValueFallbackToRuntime(type, invocation);
     }
 
     final typeArguments = type.typeArguments;
@@ -1599,24 +1602,47 @@ class _MockClassInfo {
     }).genericClosure;
   }
 
+  Expression _dummyFakedValue(
+      analyzer.InterfaceType dartType, Expression invocation) {
+    final elementToFake = dartType.element;
+    final fakeName = mockLibraryInfo._fakeNameFor(elementToFake);
+    // Only make one fake class for each class that needs to be faked.
+    if (!mockLibraryInfo.fakedInterfaceElements.contains(elementToFake)) {
+      _addFakeClass(fakeName, elementToFake);
+    }
+    final typeArguments = dartType.typeArguments;
+    return TypeReference((b) {
+      b
+        ..symbol = fakeName
+        ..types.addAll(typeArguments.map(_typeReference));
+    }).newInstance([refer('this'), invocation]);
+  }
+
   Expression _dummyValueImplementing(
       analyzer.InterfaceType dartType, Expression invocation) {
     final elementToFake = dartType.element;
     if (elementToFake is EnumElement) {
       return _typeReference(dartType).property(
           elementToFake.fields.firstWhere((f) => f.isEnumConstant).name);
+    } else if (elementToFake is ClassElement) {
+      if (elementToFake.isBase ||
+          elementToFake.isFinal ||
+          elementToFake.isSealed) {
+        // This class can't be faked, so try to call `dummyValue` to get
+        // a dummy value at run time.
+        // TODO(yanok): Consider checking subtypes, maybe some of them are
+        // implementable.
+        return _dummyValueFallbackToRuntime(dartType, invocation);
+      }
+      return _dummyFakedValue(dartType, invocation);
+    } else if (elementToFake is MixinElement) {
+      // This is a mixin and not a class. This should not happen in Dart 3,
+      // since it is not possible to have a value of mixin type. But we
+      // have to support this for reverse comptatibility.
+      return _dummyFakedValue(dartType, invocation);
     } else {
-      final fakeName = mockLibraryInfo._fakeNameFor(elementToFake);
-      // Only make one fake class for each class that needs to be faked.
-      if (!mockLibraryInfo.fakedInterfaceElements.contains(elementToFake)) {
-        _addFakeClass(fakeName, elementToFake);
-      }
-      final typeArguments = dartType.typeArguments;
-      return TypeReference((b) {
-        b
-          ..symbol = fakeName
-          ..types.addAll(typeArguments.map(_typeReference));
-      }).newInstance([refer('this'), invocation]);
+      throw StateError("Interface type '$dartType' which is nether an enum, "
+          'nor a class, nor a mixin. This case is unknown, please report a bug.');
     }
   }
 

lib/src/dummies.dart

@@ -13,8 +13,11 @@
 // limitations under the License.
 
 import 'dart:async';
+import 'dart:collection';
 import 'dart:typed_data';
 import 'mock.dart' show FakeFunctionUsedError;
+import 'platform_dummies_js.dart'
+    if (dart.library.io) 'platform_dummies_vm.dart';
 
 // TODO(yanok): try to change these to _unreasonable_ values, for example,
 // String could totally contain an explanation.
@@ -111,6 +114,7 @@ Map<Type, DummyBuilder> _defaultDummyBuilders = {
   Float32List: (_, _i) => Float32List(0),
   Float64List: (_, _i) => Float64List(0),
   ByteData: (_, _i) => ByteData(0),
+  ...platformDummies,
 };
 
 List<Object?> _defaultDummies = [
@@ -123,6 +127,8 @@ List<Object?> _defaultDummies = [
   <Never>{},
   <Never, Never>{},
   Stream<Never>.empty(),
+  SplayTreeSet<Never>(),
+  SplayTreeMap<Never, Never>(),
 ];
 
 T? dummyValueOrNull<T>(Object parent, Invocation invocation) {

lib/src/platform_dummies_js.dart

@@ -0,0 +1,17 @@
+// Copyright 2023 Dart Mockito authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'dummies.dart' show DummyBuilder;
+
+Map<Type, DummyBuilder> platformDummies = {};

lib/src/platform_dummies_vm.dart

@@ -0,0 +1,29 @@
+// Copyright 2023 Dart Mockito authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'dart:io';
+import 'dart:isolate';
+import 'dummies.dart' show DummyBuilder;
+import 'mock.dart' show SmartFake;
+
+class FakeSendPort extends SmartFake implements SendPort {
+  FakeSendPort(super.parent, super.invocation);
+}
+
+Map<Type, DummyBuilder> platformDummies = {
+  ProcessResult: (parent, invocation) => ProcessResult(0, 0, '', '''
+dummy ProcessResult created for a call to $parent.${invocation.memberName}'''),
+  // We can't fake `Isolate`, but we can fake `SendPort`, so use it.
+  Isolate: (parent, invocation) => Isolate(FakeSendPort(parent, invocation)),
+};

test/builder/auto_mocks_test.dart

@@ -102,14 +102,10 @@ void main() {
     final packageConfig = PackageConfig([
       Package('foo', Uri.file('/foo/'),
           packageUriRoot: Uri.file('/foo/lib/'),
-          languageVersion: LanguageVersion(2, 13))
+          languageVersion: LanguageVersion(3, 0))
     ]);
-    await withEnabledExperiments(
-      () async => await testBuilder(
-          buildMocks(BuilderOptions({})), sourceAssets,
-          writer: writer, outputs: outputs, packageConfig: packageConfig),
-      ['nonfunction-type-aliases'],
-    );
+    await testBuilder(buildMocks(BuilderOptions({})), sourceAssets,
+        writer: writer, outputs: outputs, packageConfig: packageConfig);
   }
 
   /// Builds with [MockBuilder] in a package which has opted into null safety,
@@ -118,15 +114,11 @@ void main() {
     final packageConfig = PackageConfig([
       Package('foo', Uri.file('/foo/'),
           packageUriRoot: Uri.file('/foo/lib/'),
-          languageVersion: LanguageVersion(2, 13))
+          languageVersion: LanguageVersion(3, 0))
     ]);
 
-    await withEnabledExperiments(
-      () async => await testBuilder(
-          buildMocks(BuilderOptions({})), sourceAssets,
-          writer: writer, packageConfig: packageConfig),
-      ['nonfunction-type-aliases'],
-    );
+    await testBuilder(buildMocks(BuilderOptions({})), sourceAssets,
+        writer: writer, packageConfig: packageConfig);
     final mocksAsset = AssetId('foo', 'test/foo_test.mocks.dart');
     return utf8.decode(writer.assets[mocksAsset]!);
   }
@@ -2730,6 +2722,33 @@ void main() {
         hasLength(1));
   });
 
+  test('does not try to generate a fake for a final class', () async {
+    await expectSingleNonNullableOutput(dedent(r'''
+      class Foo {
+        Bar m1() => Bar();
+      }
+      final class Bar {}
+      '''), _containsAllOf('dummyValue<_i2.Bar>('));
+  });
+
+  test('does not try to generate a fake for a base class', () async {
+    await expectSingleNonNullableOutput(dedent(r'''
+      class Foo {
+        Bar m1() => Bar();
+      }
+      base class Bar {}
+      '''), _containsAllOf('dummyValue<_i2.Bar>('));
+  });
+
+  test('does not try to generate a fake for a sealed class', () async {
+    await expectSingleNonNullableOutput(dedent(r'''
+      class Foo {
+        Bar m1() => Bar();
+      }
+      sealed class Bar {}
+      '''), _containsAllOf('dummyValue<_i2.Bar>('));
+  });
+
   test('throws when GenerateMocks is given a class multiple times', () async {
     _expectBuilderThrows(
       assets: {

test/builder/custom_mocks_test.dart

@@ -110,7 +110,7 @@ void main() {
     final packageConfig = PackageConfig([
       Package('foo', Uri.file('/foo/'),
           packageUriRoot: Uri.file('/foo/lib/'),
-          languageVersion: LanguageVersion(2, 15))
+          languageVersion: LanguageVersion(3, 0))
     ]);
     await testBuilder(buildMocks(BuilderOptions({})), sourceAssets,
         writer: writer, packageConfig: packageConfig);