Convert findType -> Library#findType. (#172)

* Convert findType -> Library#findType.

* Address feedback.

* Oops.

Author: matanlurey

CHANGELOG.md

@@ -40,13 +40,17 @@
     sdk: '>=1.25.0 <2.0.0'
   ```
 
-* 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`:
+* Added `LibraryReader`, a utility class for `LibraryElement` that exposes
+  high-level APIs, including `findType`, which 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');
+    var library = new LibraryReader(pkgSourceGen);
+  
+    // Instead of pkgSourceGen.getType('Generator'), which is null.
+    library.findType('Generator');
   }
   ```
 

lib/source_gen.dart

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

lib/src/find_type.dart

@@ -0,0 +1,25 @@
+// 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';
+
+/// A high-level wrapper API with common functionality for [LibraryElement].
+class LibraryReader {
+  final LibraryElement _element;
+
+  Namespace _namespaceCache;
+
+  LibraryReader(this._element);
+
+  Namespace get _namespace => _namespaceCache ??=
+      new NamespaceBuilder().createExportNamespaceForLibrary(_element);
+
+  /// Returns a top-level [ClassElement] publicly visible in by [name].
+  ///
+  /// Unlike [LibraryElement.getType], this also correctly traverses identifiers
+  /// that are accessible via one or more `export` directives.
+  ClassElement findType(String name) =>
+      _element.getType(name) ?? _namespace.get(name) as ClassElement;
+}

lib/src/library.dart

@@ -8,7 +8,7 @@ import 'package:source_gen/source_gen.dart';
 import 'package:test/test.dart';
 
 void main() {
-  LibraryElement library;
+  LibraryReader library;
 
   setUpAll(() async {
     final resolver = await resolveSource(r'''
@@ -20,24 +20,24 @@ void main() {
       
       class Example {}
     ''');
-    library = resolver.getLibraryByName('test_lib');
+    library = new LibraryReader(resolver.getLibraryByName('test_lib'));
   });
 
   final isClassElement = const isInstanceOf<ClassElement>();
 
   test('should return a type not exported', () {
-    expect(findType(library, 'Example'), isClassElement);
+    expect(library.findType('Example'), isClassElement);
   });
 
   test('should return a type exported from dart:', () {
-    expect(findType(library, 'LinkedHashMap'), isClassElement);
+    expect(library.findType('LinkedHashMap'), isClassElement);
   });
 
   test('should return a type exported from package:', () {
-    expect(findType(library, 'Generator'), isClassElement);
+    expect(library.findType('Generator'), isClassElement);
   });
 
   test('should not return a type imported', () {
-    expect(findType(library, 'Stream'), isNull);
+    expect(library.findType('Stream'), isNull);
   });
 }

test/find_type_test.dart

@@ -36,11 +36,12 @@ void main() {
     staticHashMap = collection.getType('HashMap').type;
     staticHashMapChecker = new TypeChecker.fromStatic(staticHashMap);
 
-    final sourceGen = resolver.getLibraryByName('source_gen');
-    staticGenerator = findType(sourceGen, 'Generator').type;
+    final sourceGen =
+        new LibraryReader(resolver.getLibraryByName('source_gen'));
+    staticGenerator = sourceGen.findType('Generator').type;
     staticGeneratorChecker = new TypeChecker.fromStatic(staticGenerator);
     staticGeneratorForAnnotation =
-        findType(sourceGen, 'GeneratorForAnnotation').type;
+        sourceGen.findType('GeneratorForAnnotation').type;
     staticGeneratorForAnnotationChecker =
         new TypeChecker.fromStatic(staticGeneratorForAnnotation);
   });