merge the null safety branch into master (flutter#65)

* opt into null safety

* allow Future?, add example

* update versions

* update SDK constraint for null safety

* update sdk constraint

Co-authored-by: David Morgan <davidmorgan@google.com>
Co-authored-by: Kevin Moore <kevmoo@google.com>

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.10.0-nnbd
+
+- Migrate to null safety.
+
 ## 1.9.2
 
 Revert changes in `1.9.1` due to problems moving `unawaited` to `meta`.

analysis_options.yaml

@@ -6,3 +6,6 @@
 # including a list of lints that are intentionally _not_ enforced.
 
 include: lib/analysis_options.yaml
+analyzer:
+  enable-experiment:
+    - non-nullable

example/example.dart

@@ -0,0 +1,16 @@
+import 'package:pedantic/pedantic.dart';
+
+void main() async {
+  // Normally, calling a function that returns a Future from an async method
+  // would require you to ignore the unawaited_futures lint with this analyzer
+  // syntax:
+  //
+  // ignore: unawaited_futures
+  doSomethingAsync();
+
+  // Wrapping it in a call to `unawaited` avoids that, since it doesn't
+  // return a Future. This is more explicit, and harder to get wrong.
+  unawaited(doSomethingAsync());
+}
+
+Future<void> doSomethingAsync() async {}

lib/pedantic.dart

@@ -22,4 +22,4 @@ import 'dart:async' show Future;
 ///   unawaited(log('Preferences saved!'));
 /// }
 /// ```
-void unawaited(Future<void> future) {}
+void unawaited(Future<void>? future) {}

pubspec.yaml

@@ -1,11 +1,8 @@
 name: pedantic
-version: 1.9.2
+version: 1.10.0-nnbd
 description: >-
   The Dart analyzer settings and best practices used internally at Google.
 homepage: https://github.com/dart-lang/pedantic
 
 environment:
-  sdk: '>=2.1.1 <3.0.0'
-
-dependencies:
-  meta: ^1.2.2
+  sdk: '>=2.9.0-18.0 <2.9.0'