Add findType, and fix a bug in TypeChecker.

CHANGELOG.md

@@ -34,6 +34,16 @@
 
   In Dart SDK `>=1.25.0` this can be relaxed as `part of` can refer to a path.
 
+* Added `findType`, an utility method for `LibraryElement#getType` that also
+  traverses `export` directives for publicly exported types. For example, to
+  find `Generator` from `package:source_gen/source_gen.dart`:
+
+  ```dart
+  void example(LibraryElement pkgSourceGen) {
+    findType(pkgSourceGen, 'Generator');
+  }
+  ```
+
 ## 0.5.8
 
 * Add `formatOutput` optional parameter to the `GeneratorBuilder` constructor.

lib/source_gen.dart

@@ -5,6 +5,7 @@
 library source_gen;
 
 export 'src/builder.dart';
+export 'src/find_type.dart' show findType;
 export 'src/generator.dart';
 export 'src/generator_for_annotation.dart';
 export 'src/type_checker.dart' show TypeChecker;

lib/src/find_type.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2017, 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/element/element.dart';
+import 'package:analyzer/src/dart/resolver/scope.dart';
+
+final _namespaceCache = new Expando<Namespace>();
+
+/// Returns a top-level [ClassElement] publicly visible in [library] by [name].
+///
+/// Unlike [LibraryElement.getType], this also correctly traverses identifiers
+/// that are accessible via one or more `export` directives.
+ClassElement findType(LibraryElement library, String name) =>
+    library.getType(name) ??
+    (_namespaceCache[library] ??=
+            new NamespaceBuilder().createExportNamespaceForLibrary(library))
+        .get(name) as ClassElement;

lib/src/type_checker.dart

@@ -28,6 +28,12 @@ abstract class TypeChecker {
   ///   'dart:collection#LinkedHashMap',
   /// );
   /// ```
+  ///
+  /// **NOTE**: This is considered a more _brittle_ way of determining the type
+  /// because it relies on knowing the _absolute_ path (i.e. after resolved
+  /// `export` directives). You should ideally only use `fromUrl` when you know
+  /// the full path (likely you own/control the package) or it is in a stable
+  /// package like in the `dart:` SDK.
   const factory TypeChecker.fromUrl(dynamic url) = _UriTypeChecker;
 
   /// Returns the first constant annotating [element] that is this type.
@@ -170,7 +176,7 @@ class _UriTypeChecker extends TypeChecker {
   int get hashCode => _url.hashCode;
 
   /// Url as a [Uri] object, lazily constructed.
-  Uri get uri => _cache[this] ??= Uri.parse(_url);
+  Uri get uri => _cache[this] ??= _normalizeUrl(Uri.parse(_url));
 
   /// Returns whether this type represents the same as [url].
   bool hasSameUrl(dynamic url) =>

test/find_type_test.dart

@@ -0,0 +1,43 @@
+// Copyright (c) 2017, 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/element/element.dart';
+import 'package:build_test/build_test.dart';
+import 'package:source_gen/source_gen.dart';
+import 'package:test/test.dart';
+
+void main() {
+  LibraryElement library;
+
+  setUpAll(() async {
+    final resolver = await resolveSource(r'''
+      library test_lib;
+      
+      export 'dart:collection' show LinkedHashMap;
+      export 'package:source_gen/source_gen.dart' show Generator;
+      import 'dart:async' show Stream;
+      
+      class Example {}
+    ''');
+    library = resolver.getLibraryByName('test_lib');
+  });
+
+  final isClassElement = const isInstanceOf<ClassElement>();
+
+  test('should return a type not exported', () {
+    expect(findType(library, 'Example'), isClassElement);
+  });
+
+  test('should return a type exported from dart:', () {
+    expect(findType(library, 'LinkedHashMap'), isClassElement);
+  });
+
+  test('should return a type exported from package:', () {
+    expect(findType(library, 'Generator'), isClassElement);
+  });
+
+  test('should not return a type imported', () {
+    expect(findType(library, 'Stream'), isNull);
+  });
+}

test/type_checker_test.dart

@@ -17,8 +17,16 @@ void main() {
   TypeChecker staticMapChecker;
   TypeChecker staticHashMapChecker;
 
+  // Resolved top-level types from package:source_gen.
+  DartType staticGenerator;
+  DartType staticGeneratorForAnnotation;
+  TypeChecker staticGeneratorChecker;
+  TypeChecker staticGeneratorForAnnotationChecker;
+
   setUpAll(() async {
-    final resolver = await resolveSource('');
+    final resolver = await resolveSource(r'''
+      export 'package:source_gen/source_gen.dart';
+    ''');
 
     final core = resolver.getLibraryByName('dart.core');
     staticMap = core.getType('Map').type;
@@ -27,12 +35,22 @@ void main() {
     final collection = resolver.getLibraryByName('dart.collection');
     staticHashMap = collection.getType('HashMap').type;
     staticHashMapChecker = new TypeChecker.fromStatic(staticHashMap);
+
+    final sourceGen = resolver.getLibraryByName('source_gen');
+    staticGenerator = findType(sourceGen, 'Generator').type;
+    staticGeneratorChecker = new TypeChecker.fromStatic(staticGenerator);
+    staticGeneratorForAnnotation =
+        findType(sourceGen, 'GeneratorForAnnotation').type;
+    staticGeneratorForAnnotationChecker =
+        new TypeChecker.fromStatic(staticGeneratorForAnnotation);
   });
 
   // Run a common set of type comparison checks with various implementations.
   void commonTests({
     @required TypeChecker checkMap(),
     @required TypeChecker checkHashMap(),
+    @required TypeChecker checkGenerator(),
+    @required TypeChecker checkGeneratorForAnnotation(),
   }) {
     group('(Map)', () {
       test('should equal dart:core#Map', () {
@@ -72,24 +90,60 @@ void main() {
         expect(checkHashMap().isAssignableFromType(staticMap), isFalse);
       });
     });
+
+    group('(Generator)', () {
+      test('should equal Generator', () {
+        expect(checkGenerator().isExactlyType(staticGenerator), isTrue,
+            reason: '${checkGenerator()} != $staticGenerator');
+      });
+
+      test('should not be a super type of Generator', () {
+        expect(checkGenerator().isSuperTypeOf(staticGenerator), isFalse,
+            reason: '${checkGenerator()} is super of $staticGenerator');
+      });
+
+      test('should be a super type of GeneratorForAnnotation', () {
+        expect(checkGenerator().isSuperTypeOf(staticGeneratorForAnnotation),
+            isTrue,
+            reason:
+                '${checkGenerator()} is not super of $staticGeneratorForAnnotation');
+      });
+
+      test('should be assignable from GeneratorForAnnotation', () {
+        expect(
+            checkGenerator().isAssignableFromType(staticGeneratorForAnnotation),
+            isTrue,
+            reason:
+                '${checkGenerator()} is not assignable from $staticGeneratorForAnnotation');
+      });
+    });
   }
 
   group('TypeChecker.forRuntime', () {
     commonTests(
         checkMap: () => const TypeChecker.fromRuntime(Map),
-        checkHashMap: () => const TypeChecker.fromRuntime(HashMap));
+        checkHashMap: () => const TypeChecker.fromRuntime(HashMap),
+        checkGenerator: () => const TypeChecker.fromRuntime(Generator),
+        checkGeneratorForAnnotation: () =>
+            const TypeChecker.fromRuntime(GeneratorForAnnotation));
   });
 
   group('TypeChecker.forStatic', () {
     commonTests(
         checkMap: () => staticMapChecker,
-        checkHashMap: () => staticHashMapChecker);
+        checkHashMap: () => staticHashMapChecker,
+        checkGenerator: () => staticGeneratorChecker,
+        checkGeneratorForAnnotation: () => staticGeneratorForAnnotationChecker);
   });
 
   group('TypeChecker.fromUrl', () {
     commonTests(
         checkMap: () => const TypeChecker.fromUrl('dart:core#Map'),
         checkHashMap: () =>
-            const TypeChecker.fromUrl('dart:collection#HashMap'));
+            const TypeChecker.fromUrl('dart:collection#HashMap'),
+        checkGenerator: () => const TypeChecker.fromUrl(
+            'package:source_gen/src/generator.dart#Generator'),
+        checkGeneratorForAnnotation: () => const TypeChecker.fromUrl(
+            'package:source_gen/src/generator_for_annotation.dart#GeneratorForAnnotation'));
   });
 }