Add TypeChecker.any (#202)

* Add annotationsOfExact.

* Add type checks.

* Update CHANGELOG.

* Add TypeChecker.any.

* CHANGELOG.

* .

CHANGELOG.md

@@ -8,6 +8,9 @@
 * `TypeChecker#annotations...`-methods now throw a `StateError` if one or more
   annotations on an element are not resolvable. This is usually a sign of a
   mispelling, missing import, or missing dependency.
+
+* Added `TypeChecker.any`, which delegates to multiple other `TypeChecker`
+  implementations when making a type check.
 
 ## 0.5.10+1
 

lib/src/type_checker.dart

@@ -14,6 +14,20 @@ import 'utils.dart';
 abstract class TypeChecker {
   const TypeChecker._();
 
+  /// Creates a new [TypeChecker] that delegates to other [checkers].
+  ///
+  /// This implementation will return `true` for type checks if _any_ of the
+  /// provided type checkers return true, which is useful for deprecating an
+  /// API:
+  /// ```dart
+  /// const $Foo = const TypeChecker.fromRuntime(Foo);
+  /// const $Bar = const TypeChecker.fromRuntime(Bar);
+  ///
+  /// // Used until $Foo is deleted.
+  /// const $FooOrBar = const TypeChecker.forAny(const [$Foo, $Bar]);
+  /// ```
+  const factory TypeChecker.any(Iterable<TypeChecker> checkers) = _AnyChecker;
+
   /// Create a new [TypeChecker] backed by a runtime [type].
   ///
   /// This implementation uses `dart:mirrors` (runtime reflection).
@@ -71,14 +85,13 @@ abstract class TypeChecker {
   /// Returns annotating constants on [element] assignable to this type.
   Iterable<DartObject> annotationsOf(Element element) => element.metadata
       .map(_checkedConstantValue)
-      .where((a) => isAssignableFromType(a.type));
+      .where((a) => a?.type != null && isAssignableFromType(a.type));
 
   /// Returns annotating constants on [element] of exactly this type.
   Iterable<DartObject> annotationsOfExact(Element element) => element.metadata
       .map(_checkedConstantValue)
-      .where((a) => a?.type != null && isAssignableFromType(a.type));
+      .where((a) => a?.type != null && isExactlyType(a.type));
 
-  /// Returns `true` if the type of [element] can be assigned to this type.
   /// Returns `true` if the type of [element] can be assigned to this type.
   bool isAssignableFrom(Element element) =>
       isExactly(element) || _getAllSupertypes(element).any(isExactlyType);
@@ -210,3 +223,12 @@ class _UriTypeChecker extends TypeChecker {
   @override
   String toString() => '${uri}';
 }
+
+class _AnyChecker extends TypeChecker {
+  final Iterable<TypeChecker> _checkers;
+
+  const _AnyChecker(this._checkers) : super._();
+
+  @override
+  bool isExactly(Element element) => _checkers.any((c) => c.isExactly(element));
+}

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 0.6.0-dev
+version: 0.6.0
 author: Dart Team <[email protected]>
 description: Automated source code generation for Dart.
 homepage: https://github.com/dart-lang/source_gen

test/type_checker_test.dart

@@ -180,7 +180,7 @@ void main() {
             'package:source_gen/src/generator_for_annotation.dart#GeneratorForAnnotation'));
   });
 
-  test('should gracefully when something is not resolvable', () async {
+  test('should fail gracefully when something is not resolvable', () async {
     final resolver = await resolveSource(r'''
       library _test;
 
@@ -194,4 +194,12 @@ void main() {
     expect(() => $deprecated.annotationsOf(classX), throwsStateError,
         reason: 'deprecated was spelled wrong; no annotation can be resolved');
   });
+
+  test('should check multiple checkers', () {
+    final listOrMap = const TypeChecker.any(const [
+      const TypeChecker.fromRuntime(List),
+      const TypeChecker.fromRuntime(Map),
+    ]);
+    expect(listOrMap.isExactlyType(staticMap), isTrue);
+  });
 }