Avoid name conflicts with dart:core

The primary mechanism here is a custom code_builder Allocator.

Prefixing _all_ 'dart:core' elements would make the generated code quite unreadable. Code would look like:

```dart
@_i3.override
_i3.Future<_i3.bool> List(_i3.Map<_i3.String, _i3.int> p) { ... }
```

This PR instead gathers all members which would conflict with an element exported from 'dart:core', and only prefixes those elements. In this way, most code is unchanged. The only, very rare, cases of prefixing 'dart:core', are for members named things like 'List'.

PiperOrigin-RevId: 459549619

Author: srawlins

pkgs/mockito/lib/src/builder.dart

@@ -108,8 +108,11 @@ class MockBuilder implements Builder {
       b.body.addAll(mockLibraryInfo.mockClasses);
     });
 
-    final emitter = DartEmitter.scoped(
-        orderDirectives: true, useNullSafetySyntax: sourceLibIsNonNullable);
+    final emitter = DartEmitter(
+        allocator: _AvoidConflictsAllocator(
+            coreConflicts: mockLibraryInfo.coreConflicts),
+        orderDirectives: true,
+        useNullSafetySyntax: sourceLibIsNonNullable);
     final rawOutput = mockLibrary.accept(emitter).toString();
     // 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
@@ -816,13 +819,22 @@ class _MockLibraryInfo {
   /// Asset-resolving while building the mock library.
   final Map<Element, String> assetUris;
 
+  final LibraryElement? dartCoreLibrary;
+
+  /// Names of overridden members which conflict with elements exported from
+  /// 'dart:core'.
+  ///
+  /// Each of these must be imported with a prefix to avoid the conflict.
+  final coreConflicts = <String>{};
+
   /// Build mock classes for [mockTargets].
   _MockLibraryInfo(
     Iterable<_MockTarget> mockTargets, {
     required this.assetUris,
     required LibraryElement entryLib,
     required InheritanceManager3 inheritanceManager,
-  }) {
+  }) : dartCoreLibrary = entryLib.importedLibraries
+            .firstWhereOrNull((library) => library.isDartCore) {
     for (final mockTarget in mockTargets) {
       final fallbackGenerators = mockTarget.fallbackGenerators;
       mockClasses.add(_MockClassInfo(
@@ -1013,11 +1025,18 @@ class _MockClassInfo {
       if (typeSystem._returnTypeIsNonNullable(method) ||
           typeSystem._hasNonNullableParameter(method) ||
           _needsOverrideForVoidStub(method)) {
+        _checkForConflictWithCore(method.name);
         yield Method((mBuilder) => _buildOverridingMethod(mBuilder, method));
       }
     }
   }
 
+  void _checkForConflictWithCore(String name) {
+    if (mockLibraryInfo.dartCoreLibrary?.exportNamespace.get(name) != null) {
+      mockLibraryInfo.coreConflicts.add(name);
+    }
+  }
+
   /// The default behavior of mocks is to return null for unstubbed methods. To
   /// use the new behavior of throwing an error, we must explicitly call
   /// `throwOnMissingStub`.
@@ -1036,7 +1055,7 @@ class _MockClassInfo {
     if (method.isOperator) name = 'operator$name';
     builder
       ..name = name
-      ..annotations.addAll([refer('override')])
+      ..annotations.add(referImported('override', 'dart:core'))
       ..returns = _typeReference(method.returnType)
       ..types.addAll(method.typeParameters.map(_typeParameterReference));
 
@@ -1105,7 +1124,8 @@ class _MockClassInfo {
       return;
     }
 
-    final invocation = refer('Invocation').property('method').call([
+    final invocation =
+        referImported('Invocation', 'dart:core').property('method').call([
       refer('#${method.displayName}'),
       literalList(invocationPositionalArgs),
       if (invocationNamedArgs.isNotEmpty) literalMap(invocationNamedArgs),
@@ -1202,6 +1222,7 @@ class _MockClassInfo {
       return TypeReference((b) {
         b
           ..symbol = 'Stream'
+          ..url = 'dart:async'
           ..types.add(elementType);
       }).property('empty').call([]);
     } else if (type.isDartCoreString) {
@@ -1224,7 +1245,9 @@ class _MockClassInfo {
   /// Returns a reference to [Future], optionally with a type argument for the
   /// value of the Future.
   TypeReference _futureReference([Reference? valueType]) => TypeReference((b) {
-        b.symbol = 'Future';
+        b
+          ..symbol = 'Future'
+          ..url = 'dart:async';
         if (valueType != null) {
           b.types.add(valueType);
         }
@@ -1513,7 +1536,7 @@ class _MockClassInfo {
       MethodBuilder builder, PropertyAccessorElement getter) {
     builder
       ..name = getter.displayName
-      ..annotations.addAll([refer('override')])
+      ..annotations.add(referImported('override', 'dart:core'))
       ..type = MethodType.getter
       ..returns = _typeReference(getter.returnType);
 
@@ -1540,7 +1563,8 @@ class _MockClassInfo {
       return;
     }
 
-    final invocation = refer('Invocation').property('getter').call([
+    final invocation =
+        referImported('Invocation', 'dart:core').property('getter').call([
       refer('#${getter.displayName}'),
     ]);
     final namedArgs = {
@@ -1566,7 +1590,7 @@ class _MockClassInfo {
       MethodBuilder builder, PropertyAccessorElement setter) {
     builder
       ..name = setter.displayName
-      ..annotations.addAll([refer('override')])
+      ..annotations.add(referImported('override', 'dart:core'))
       ..type = MethodType.setter;
 
     assert(setter.parameters.length == 1);
@@ -1576,7 +1600,8 @@ class _MockClassInfo {
       ..type = _typeReference(parameter.type, forceNullable: true)));
     final invocationPositionalArg = refer(parameter.displayName);
 
-    final invocation = refer('Invocation').property('setter').call([
+    final invocation =
+        referImported('Invocation', 'dart:core').property('setter').call([
       refer('#${setter.displayName}'),
       invocationPositionalArg,
     ]);
@@ -1714,6 +1739,57 @@ class InvalidMockitoAnnotationException implements Exception {
   String toString() => 'Invalid @GenerateMocks annotation: $message';
 }
 
+/// An [Allocator] that avoids conflicts with elements exported from
+/// 'dart:core'.
+///
+/// This does not prefix _all_ 'dart:core' elements; instead it takes a set of
+/// names which conflict, and if that is non-empty, generates two import
+/// directives for 'dart:core':
+///
+/// * an unprefixed import with conflicting names enumerated in the 'hide'
+///   combinator,
+/// * a prefixed import which will be the way to reference the conflicting
+///   names.
+class _AvoidConflictsAllocator implements Allocator {
+  final _imports = <String, int>{};
+  var _keys = 1;
+
+  /// The collection of names of elements which conflict with elements exported
+  /// from 'dart:core'.
+  final Set<String> _coreConflicts;
+
+  _AvoidConflictsAllocator({required Set<String> coreConflicts})
+      : _coreConflicts = coreConflicts;
+
+  @override
+  String allocate(Reference reference) {
+    final symbol = reference.symbol!;
+    final url = reference.url;
+    if (url == null) {
+      return symbol;
+    }
+    if (url == 'dart:core' && !_coreConflicts.contains(symbol)) {
+      return symbol;
+    }
+    return '_i${_imports.putIfAbsent(url, _nextKey)}.$symbol';
+  }
+
+  int _nextKey() => _keys++;
+
+  @override
+  Iterable<Directive> get imports => [
+        if (_imports.containsKey('dart:core'))
+          // 'dart:core' is explicitly imported to avoid a conflict between an
+          // overriding member and an element exported by 'dart:core'. We must
+          // add another, unprefixed, import for 'dart:core' which hides the
+          // conflicting names.
+          Directive.import('dart:core', hide: _coreConflicts.toList()),
+        ..._imports.keys.map(
+          (u) => Directive.import(u, as: '_i${_imports[u]}'),
+        ),
+      ];
+}
+
 /// A [MockBuilder] instance for use by `build.yaml`.
 Builder buildMocks(BuilderOptions options) => MockBuilder();
 

pkgs/mockito/test/builder/auto_mocks_test.dart

@@ -534,8 +534,8 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Future<void> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Future<void>.value(),
-          returnValueForMissingStub: Future<void>.value()) as _i3.Future<void>);
+          returnValue: _i3.Future<void>.value(),
+          returnValueForMissingStub: _i3.Future<void>.value()) as _i3.Future<void>);
       ''')),
     );
   });
@@ -549,7 +549,7 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Stream<int> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Stream<int>.empty()) as _i3.Stream<int>);
+          returnValue: _i3.Stream<int>.empty()) as _i3.Stream<int>);
       ''')),
     );
   });
@@ -715,6 +715,25 @@ void main() {
     );
   });
 
+  test('overrides methods, adjusting imports for names that conflict with core',
+      () async {
+    await expectSingleNonNullableOutput(
+        dedent('''
+      import 'dart:core' as core;
+      class Foo {
+        void List(core.int a) {}
+        core.List<core.String> m() => [];
+      }
+      '''),
+        _containsAllOf(
+          '  void List(int? a) => super.noSuchMethod(Invocation.method(#List, [a]),\n',
+          dedent2('''
+            _i3.List<String> m() =>
+                (super.noSuchMethod(Invocation.method(#m, []), returnValue: <String>[])
+                    as _i3.List<String>);'''),
+        ));
+  });
+
   test(
       'overrides `toString` with a correct signature if the class overrides '
       'it', () async {
@@ -1257,6 +1276,23 @@ void main() {
     expect(mocksContent, contains('m(_i3.Bar? a)'));
   });
 
+  test('imports dart:core with a prefix when members conflict with dart:core',
+      () async {
+    await expectSingleNonNullableOutput(
+      dedent('''
+      import 'dart:core' as core;
+      class Foo {
+        void List(int a) {}
+        core.List<String> m() => [];
+      }
+      '''),
+      _containsAllOf(
+        "import 'dart:core' hide List;",
+        "import 'dart:core' as _i3;",
+      ),
+    );
+  });
+
   test('prefixes parameter type on generic function-typed parameter', () async {
     await expectSingleNonNullableOutput(
       dedent(r'''
@@ -1492,7 +1528,7 @@ void main() {
         '''),
       _containsAllOf(
           '_i3.FutureOr<R> m<R>() => (super.noSuchMethod(Invocation.method(#m, []),',
-          '      returnValue: Future<R>.value(null)) as _i3.FutureOr<R>);'),
+          '      returnValue: _i3.Future<R>.value(null)) as _i3.FutureOr<R>);'),
     );
   });
 
@@ -2148,7 +2184,7 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Future<bool> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Future<bool>.value(false)) as _i3.Future<bool>);
+          returnValue: _i3.Future<bool>.value(false)) as _i3.Future<bool>);
       ''')),
     );
   });
@@ -2164,7 +2200,7 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Future<Function> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Future<Function>.value(() {})) as _i3.Future<Function>);
+          returnValue: _i3.Future<Function>.value(() {})) as _i3.Future<Function>);
       ''')),
     );
   });
@@ -2180,7 +2216,7 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Future<_i2.Bar?> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Future<_i2.Bar?>.value()) as _i3.Future<_i2.Bar?>);
+          returnValue: _i3.Future<_i2.Bar?>.value()) as _i3.Future<_i2.Bar?>);
       ''')),
     );
   });
@@ -2198,7 +2234,7 @@ void main() {
       _containsAllOf(dedent2('''
       _i3.Future<_i4.Uint8List> m() =>
           (super.noSuchMethod(Invocation.method(#m, []),
-                  returnValue: Future<_i4.Uint8List>.value(_i4.Uint8List(0)))
+                  returnValue: _i3.Future<_i4.Uint8List>.value(_i4.Uint8List(0)))
               as _i3.Future<_i4.Uint8List>);
       ''')),
     );
@@ -2216,7 +2252,7 @@ void main() {
       _containsAllOf(dedent2('''
       _i3.Future<Iterable<bool>> m() =>
           (super.noSuchMethod(Invocation.method(#m, []),
-                  returnValue: Future<Iterable<bool>>.value(<bool>[]))
+                  returnValue: _i3.Future<Iterable<bool>>.value(<bool>[]))
               as _i3.Future<Iterable<bool>>);
       ''')),
     );
@@ -2231,7 +2267,7 @@ void main() {
       '''),
       _containsAllOf(dedent2('''
       _i3.Stream<int> m() => (super.noSuchMethod(Invocation.method(#m, []),
-          returnValue: Stream<int>.empty()) as _i3.Stream<int>);
+          returnValue: _i3.Stream<int>.empty()) as _i3.Stream<int>);
       ''')),
     );
   });