Add a hint when Future is imported from core in code targeted to run with an SDK prior to 2.1

Change-Id: I925412b9c7c3023836a0a2a7d3d00847adf0b0c7
Reviewed-on: https://dart-review.googlesource.com/c/84547
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/error/error.dart

@@ -320,6 +320,7 @@ const List<ErrorCode> errorCodeValues = const [
   HintCode.OVERRIDE_ON_NON_OVERRIDING_METHOD,
   HintCode.OVERRIDE_ON_NON_OVERRIDING_SETTER,
   HintCode.PACKAGE_IMPORT_CONTAINS_DOT_DOT,
+  HintCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE,
   HintCode.TYPE_CHECK_IS_NOT_NULL,
   HintCode.TYPE_CHECK_IS_NULL,
   HintCode.UNDEFINED_GETTER,

pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart

@@ -8,6 +8,7 @@ import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
+import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/file_state.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
@@ -25,41 +26,54 @@ import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error_verifier.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer/src/hint/sdk_constraint_extractor.dart';
+import 'package:analyzer/src/hint/sdk_constraint_verifier.dart';
 import 'package:analyzer/src/lint/linter.dart';
 import 'package:analyzer/src/lint/linter_visitor.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/strong/checker.dart';
+import 'package:pub_semver/pub_semver.dart';
 
 /**
  * Analyzer of a single library.
  */
 class LibraryAnalyzer {
+  /// A marker object used to prevent the initialization of
+  /// [_versionConstraintFromPubspec] when the previous initialization attempt
+  /// failed.
+  static final VersionRange noSpecifiedRange = new VersionRange();
   final AnalysisOptionsImpl _analysisOptions;
   final DeclaredVariables _declaredVariables;
   final SourceFactory _sourceFactory;
   final FileState _library;
-  final InheritanceManager2 _inheritance;
 
+  final InheritanceManager2 _inheritance;
   final bool Function(Uri) _isLibraryUri;
   final AnalysisContext _context;
   final ElementResynthesizer _resynthesizer;
   final TypeProvider _typeProvider;
+
   final TypeSystem _typeSystem;
-
   LibraryElement _libraryElement;
+
   LibraryScope _libraryScope;
-
   final Map<FileState, LineInfo> _fileToLineInfo = {};
-  final Map<FileState, IgnoreInfo> _fileToIgnoreInfo = {};
 
+  final Map<FileState, IgnoreInfo> _fileToIgnoreInfo = {};
   final Map<FileState, RecordingErrorListener> _errorListeners = {};
   final Map<FileState, ErrorReporter> _errorReporters = {};
   final List<UsedImportedElements> _usedImportedElementsList = [];
   final List<UsedLocalElements> _usedLocalElementsList = [];
   final Map<FileState, List<PendingError>> _fileToPendingErrors = {};
+
   final Set<ConstantEvaluationTarget> _constants = new Set();
 
+  /// The cached version range for the SDK specified in `pubspec.yaml`, or
+  /// [noSpecifiedRange] if there is no `pubspec.yaml` or if it does not contain
+  /// an SDK range. Use [versionConstraintFromPubspec] to access this field.
+  VersionConstraint _versionConstraintFromPubspec;
+
   LibraryAnalyzer(
       this._analysisOptions,
       this._declaredVariables,
@@ -159,6 +173,20 @@ class LibraryAnalyzer {
     return results;
   }
 
+  VersionConstraint versionConstraintFromPubspec() {
+    if (_versionConstraintFromPubspec == null) {
+      _versionConstraintFromPubspec = noSpecifiedRange;
+      File pubspecFile = _findPubspecFile(_library);
+      if (pubspecFile != null) {
+        SdkConstraintExtractor extractor =
+            new SdkConstraintExtractor(pubspecFile);
+        _versionConstraintFromPubspec =
+            extractor.constraint() ?? noSpecifiedRange;
+      }
+    }
+    return _versionConstraintFromPubspec;
+  }
+
   void _computeConstantErrors(
       ErrorReporter errorReporter, CompilationUnit unit) {
     ConstantVerifier constantVerifier = new ConstantVerifier(
@@ -233,6 +261,16 @@ class LibraryAnalyzer {
           new UnusedLocalElementsVerifier(errorListener, usedElements);
       unit.accept(visitor);
     }
+    //
+    // Find code that uses features from an SDK that is newer than the minimum
+    // version allowed in the pubspec.yaml file.
+    //
+    VersionRange versionRange = versionConstraintFromPubspec();
+    if (versionRange != noSpecifiedRange) {
+      SdkConstraintVerifier verifier = new SdkConstraintVerifier(
+          errorReporter, _libraryElement, _typeProvider, versionRange);
+      unit.accept(verifier);
+    }
   }
 
   void _computeLints(FileState file, LinterContextUnit currentUnit,
@@ -364,6 +402,20 @@ class LibraryAnalyzer {
     _constants.addAll(dependenciesFinder.dependencies);
   }
 
+  File _findPubspecFile(FileState file) {
+    ResourceProvider resourceProvider =
+        _libraryElement.session?.resourceProvider;
+    Folder folder = resourceProvider?.getFile(file.path)?.parent;
+    while (folder != null) {
+      File pubspecFile = folder.getChildAssumingFile('pubspec.yaml');
+      if (pubspecFile.exists) {
+        return pubspecFile;
+      }
+      folder = folder.parent;
+    }
+    return null;
+  }
+
   RecordingErrorListener _getErrorListener(FileState file) =>
       _errorListeners.putIfAbsent(file, () => new RecordingErrorListener());
 

pkg/analyzer/lib/src/dart/error/hint_codes.dart

@@ -519,6 +519,18 @@ class HintCode extends ErrorCode {
       'PACKAGE_IMPORT_CONTAINS_DOT_DOT',
       "A package import shouldn't contain '..'.");
 
+  /**
+   * A class defined in `dart:async` that was not exported from `dart:core`
+   * before version 2.1 is being referenced via `dart:core` in code that is
+   * expected to run on earlier versions.
+   */
+  static const HintCode SDK_VERSION_ASYNC_EXPORTED_FROM_CORE = const HintCode(
+      'SDK_VERSION_ASYNC_EXPORTED_FROM_CORE',
+      "The class '{0}' was not exported from 'dart:core' until version 2.1, "
+      "but this code is required to be able to run on earlier versions.",
+      correction:
+          "Try either importing 'dart:async' or updating the SDK constraints.");
+
   /**
    * Type checks of the type `x is! Null` should be done with `x != null`.
    */

pkg/analyzer/lib/src/hint/sdk_constraint_extractor.dart

@@ -0,0 +1,55 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:yaml/yaml.dart';
+
+/// A utility class used to extract the SDK version constraint from a
+/// `pubspec.yaml` file.
+class SdkConstraintExtractor {
+  /// The file from which the constraint is to be extracted.
+  final File pubspecFile;
+
+  /// The version range that was
+  VersionConstraint _constraint;
+
+  /// Initialize a newly created extractor to extract the SDK version constraint
+  /// from the given `pubspec.yaml` file.
+  SdkConstraintExtractor(this.pubspecFile);
+
+  /// Return the range of supported versions.
+  VersionConstraint constraint() {
+    if (_constraint == null) {
+      try {
+        String constraintText = _getConstraintText();
+        if (constraintText != null) {
+          _constraint = new VersionConstraint.parse(constraintText);
+        }
+      } catch (e) {
+        // Return `null` by falling through without setting `_versionRange`.
+      }
+    }
+    return _constraint;
+  }
+
+  /// Return the constraint text following "sdk:".
+  String _getConstraintText() {
+    String fileContent = pubspecFile.readAsStringSync();
+    YamlDocument document = loadYamlDocument(fileContent);
+    YamlNode contents = document.contents;
+    if (contents is YamlMap) {
+      var environment = contents['environment'];
+      if (environment is YamlMap) {
+        var sdk = environment['sdk'];
+        if (sdk is String) {
+          return sdk;
+        } else if (sdk is YamlScalar) {
+          return sdk.toString();
+        }
+      }
+    }
+    return null;
+  }
+}

pkg/analyzer/lib/src/hint/sdk_constraint_verifier.dart

@@ -0,0 +1,68 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/error/listener.dart';
+import 'package:analyzer/src/dart/resolver/scope.dart';
+import 'package:analyzer/src/error/codes.dart';
+import 'package:analyzer/src/generated/resolver.dart';
+import 'package:pub_semver/pub_semver.dart';
+
+/// A visitor that finds code that assumes a later version of the SDK than the
+/// minimum version required by the SDK constraints in `pubspec.yaml`.
+class SdkConstraintVerifier extends RecursiveAstVisitor<void> {
+  /// The error reporter to be used to report errors.
+  final ErrorReporter _errorReporter;
+
+  /// The element representing the library containing the unit to be verified.
+  final LibraryElement _containingLibrary;
+
+  /// The typ provider used to access SDK types.
+  final TypeProvider _typeProvider;
+
+  /// The range of versions of the SDK that are allowed by the SDK constraints.
+  final VersionRange _versionRange;
+
+  /// A cached flag indicating whether references to Future and Stream need to
+  /// be checked. Use [] to access this field.
+  bool _checkFutureAndStream;
+
+  /// Initialize a newly created verifier to use the given [_errorReporter] to
+  /// report errors.
+  SdkConstraintVerifier(this._errorReporter, this._containingLibrary,
+      this._typeProvider, this._versionRange);
+
+  /// Return a range covering every version up to, but not including, 2.1.0.
+  VersionRange get before_2_1_0 =>
+      new VersionRange(max: Version.parse('2.1.0'), includeMax: false);
+
+  /// Return `true` if references to Future and Stream need to be checked.
+  bool get checkFutureAndStream =>
+      _checkFutureAndStream ??= !before_2_1_0.intersect(_versionRange).isEmpty;
+
+  @override
+  void visitSimpleIdentifier(SimpleIdentifier node) {
+    if (node.inDeclarationContext()) {
+      return;
+    }
+    Element element = node.staticElement;
+    if (checkFutureAndStream &&
+        (element == _typeProvider.futureType.element ||
+            element == _typeProvider.streamType.element)) {
+      for (LibraryElement importedLibrary
+          in _containingLibrary.importedLibraries) {
+        if (!importedLibrary.isDartCore) {
+          Namespace namespace = importedLibrary.exportNamespace;
+          if (namespace != null && namespace.get(element.name) != null) {
+            return;
+          }
+        }
+      }
+      _errorReporter.reportErrorForNode(
+          HintCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE, node, [element.name]);
+    }
+  }
+}

pkg/analyzer/test/src/hint/sdk_constraint_extractor_test.dart

@@ -0,0 +1,94 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/hint/sdk_constraint_extractor.dart';
+import 'package:analyzer/src/test_utilities/resource_provider_mixin.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(SdkConstraintExtractorTest);
+  });
+}
+
+@reflectiveTest
+class SdkConstraintExtractorTest with ResourceProviderMixin {
+  SdkConstraintExtractor extractorFor(String pubspecContent) {
+    String pubspecPath = '/pkg/test/pubspec.yaml';
+    File pubspecFile = newFile(pubspecPath, content: pubspecContent);
+    return new SdkConstraintExtractor(pubspecFile);
+  }
+
+  test_constraint_any() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: any
+''');
+    expect(extractor.constraint().toString(), 'any');
+  }
+
+  test_constraint_caret() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: ^2.1.0
+''');
+    expect(extractor.constraint().toString(), '^2.1.0');
+  }
+
+  test_constraint_compound() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: '>=2.1.0 <3.0.0'
+''');
+    expect(extractor.constraint().toString(), '>=2.1.0 <3.0.0');
+  }
+
+  test_constraint_gt() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: '>2.1.0'
+''');
+    expect(extractor.constraint().toString(), '>2.1.0');
+  }
+
+  test_constraint_gte() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: '>=2.2.0-dev.3.0'
+''');
+    expect(extractor.constraint().toString(), '>=2.2.0-dev.3.0');
+  }
+
+  test_constraint_invalid_badConstraint() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  sdk: latest
+''');
+    expect(extractor.constraint(), isNull);
+  }
+
+  test_constraint_invalid_noEnvironment() {
+    SdkConstraintExtractor extractor = extractorFor('''
+name: test
+''');
+    expect(extractor.constraint(), isNull);
+  }
+
+  test_constraint_invalid_noSdk() {
+    SdkConstraintExtractor extractor = extractorFor('''
+environment:
+  os: 'Analytical Engine'
+''');
+    expect(extractor.constraint(), isNull);
+  }
+
+  test_constraint_invalid_notYaml() {
+    SdkConstraintExtractor extractor = extractorFor('''
+class C {}
+''');
+    expect(extractor.constraint(), isNull);
+  }
+}

pkg/analyzer/test/src/hint/sdk_constraint_verifier.dart

@@ -0,0 +1,30 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/error/error.dart';
+
+import '../../generated/resolver_test_case.dart';
+import '../../generated/test_support.dart';
+
+/// A base class designed to be used by tests of the hints produced by an
+/// SdkConstraintVerifier.
+class SdkConstraintVerifierTest extends ResolverTestCase {
+  bool get enableNewAnalysisDriver => true;
+
+  verifyVersion(String version, String source,
+      {List<ErrorCode> errorCodes}) async {
+    newFile('/pubspec.yaml', content: '''
+environment:
+  sdk: ^$version
+''');
+    TestAnalysisResult result = await computeTestAnalysisResult(source);
+    GatheringErrorListener listener = new GatheringErrorListener();
+    listener.addAll(result.errors);
+    if (errorCodes == null) {
+      listener.assertNoErrors();
+    } else {
+      listener.assertErrorsWithCodes(errorCodes);
+    }
+  }
+}

pkg/analyzer/test/src/hint/sdk_version_async_exported_from_core_test.dart

@@ -0,0 +1,105 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/src/dart/error/hint_codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'sdk_constraint_verifier.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(SdkVersionAsyncExportedFromCoreTest);
+  });
+}
+
+@reflectiveTest
+class SdkVersionAsyncExportedFromCoreTest extends SdkConstraintVerifierTest {
+  test_equals_explicitImportOfAsync() async {
+    await verifyVersion('2.1.0', '''
+import 'dart:async';
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_equals_explicitImportOfCore() async {
+    await verifyVersion('2.1.0', '''
+import 'dart:core';
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_equals_explicitImportOfExportingLibrary() async {
+    addNamedSource('/exporter.dart', '''
+export 'dart:async';
+''');
+    await verifyVersion('2.1.0', '''
+import 'exporter.dart';
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_equals_implicitImportOfCore() async {
+    await verifyVersion('2.1.0', '''
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_equals_implicitImportOfCore_inPart() async {
+    newFile('/lib.dart', content: '''
+library lib;
+''');
+    await verifyVersion('2.1.0', '''
+part of lib;
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_lessThan_explicitImportOfAsync() async {
+    await verifyVersion('2.0.0', '''
+import 'dart:async';
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_lessThan_explicitImportOfCore() async {
+    await verifyVersion('2.0.0', '''
+import 'dart:core';
+
+Future<int> zero() async => 0;
+''', errorCodes: [HintCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE]);
+  }
+
+  test_lessThan_explicitImportOfExportingLibrary() async {
+    addNamedSource('/exporter.dart', '''
+export 'dart:async';
+''');
+    await verifyVersion('2.0.0', '''
+import 'exporter.dart';
+
+Future<int> zero() async => 0;
+''');
+  }
+
+  test_lessThan_implicitImportOfCore() async {
+    await verifyVersion('2.0.0', '''
+Future<int> zero() async => 0;
+''', errorCodes: [HintCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE]);
+  }
+
+  test_lessThan_implicitImportOfCore_inPart() async {
+    newFile('/lib.dart', content: '''
+library lib;
+''');
+    await verifyVersion('2.0.0', '''
+part of lib;
+
+Future<int> zero() async => 0;
+''', errorCodes: [HintCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE]);
+  }
+}

pkg/analyzer/test/src/hint/test_all.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'sdk_version_async_exported_from_core_test.dart'
+    as sdk_version_async_exported_from_core;
+
+main() {
+  defineReflectiveSuite(() {
+    sdk_version_async_exported_from_core.main();
+  }, name: 'hint');
+}

pkg/analyzer/test/src/test_all.dart

@@ -8,6 +8,7 @@ import 'command_line/test_all.dart' as command_line;
 import 'context/test_all.dart' as context;
 import 'dart/test_all.dart' as dart;
 import 'fasta/test_all.dart' as fasta;
+import 'hint/test_all.dart' as hint;
 import 'lint/test_all.dart' as lint;
 import 'pubspec/test_all.dart' as pubspec;
 import 'source/test_all.dart' as source;
@@ -22,6 +23,7 @@ main() {
     context.main();
     dart.main();
     fasta.main();
+    hint.main();
     lint.main();
     pubspec.main();
     source.main();

pkg/front_end/pubspec.yaml

@@ -6,7 +6,7 @@ author: Dart Team <misc@dartlang.org>
 description: Front end for compilation of Dart code.
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/front_end
 environment:
-  sdk: '>=2.0.0-dev.48.0 <3.0.0'
+  sdk: '>=2.1.0 <3.0.0'
 dependencies:
   charcode: '^1.1.1'
   convert: '^2.0.1'