Make AppContext API not be prone to Future oddities (#16034)

Follow-up comments to #15984

packages/flutter_tools/lib/runner.dart

@@ -196,7 +196,7 @@ Future<String> _doctorText() async {
   try {
     final BufferLogger logger = new BufferLogger();
 
-    await context.run<Future<bool>>(
+    await context.run<bool>(
       body: () => doctor.diagnose(verbose: true),
       overrides: <Type, Generator>{
         Logger: () => logger,

packages/flutter_tools/lib/src/base/context.dart

@@ -126,20 +126,20 @@ class AppContext {
   /// If [name] is specified, the child context will be assigned the given
   /// name. This is useful for debugging purposes and is analogous to naming a
   /// thread in Java.
-  V run<V>({
-    @required V body(),
+  Future<V> run<V>({
+    @required FutureOr<V> body(),
     String name,
     Map<Type, Generator> overrides,
     Map<Type, Generator> fallbacks,
-  }) {
+  }) async {
     final AppContext child = new AppContext._(
       this,
       name,
       new Map<Type, Generator>.unmodifiable(overrides ?? const <Type, Generator>{}),
       new Map<Type, Generator>.unmodifiable(fallbacks ?? const <Type, Generator>{}),
     );
-    return runZoned<V>(
-      body,
+    return await runZoned<Future<V>>(
+      () async => await body(),
       zoneValues: <_Key, AppContext>{_Key.key: child},
     );
   }

packages/flutter_tools/lib/src/commands/daemon.dart

@@ -54,7 +54,7 @@ class DaemonCommand extends FlutterCommand {
 
     Cache.releaseLockEarly();
 
-    return context.run<Future<Null>>(
+    return context.run<Null>(
       body: () async {
         final Daemon daemon = new Daemon(
             stdinCommandStream, stdoutCommandResponse,

packages/flutter_tools/lib/src/context_runner.dart

@@ -38,9 +38,9 @@ Future<T> runInContext<T>(
   FutureOr<T> runner(), {
   Map<Type, dynamic> overrides,
 }) async {
-  return await context.run<Future<T>>(
+  return await context.run<T>(
     name: 'global fallbacks',
-    body: () async => await runner(),
+    body: runner,
     overrides: overrides,
     fallbacks: <Type, Generator>{
       AndroidSdk: AndroidSdk.locateAndroidSdk,

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -225,7 +225,7 @@ abstract class FlutterCommand extends Command<Null> {
   Future<Null> run() {
     final DateTime startTime = clock.now();
 
-    return context.run<Future<Null>>(
+    return context.run<Null>(
       name: 'command',
       overrides: <Type, Generator>{FlutterCommand: () => this},
       body: () async {

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -246,7 +246,7 @@ class FlutterCommandRunner extends CommandRunner<Null> {
       });
     }
 
-    await context.run<Future<Null>>(
+    await context.run<Null>(
       overrides: contextOverrides.map<Type, Generator>((Type type, dynamic value) {
         return new MapEntry<Type, Generator>(type, () => value);
       }),

packages/flutter_tools/test/base/build_test.dart

@@ -433,7 +433,7 @@ void main() {
         depfileContent: 'output.snapshot : main.dart other.dart',
       );
 
-      await context.run(
+      await context.run<void>(
         overrides: <Type, Generator>{GenSnapshot: () => genSnapshot},
         body: () async {
           await fs.file('main.dart').writeAsString('import "other.dart";\nvoid main() {}');

packages/flutter_tools/test/base/context_test.dart

@@ -32,9 +32,9 @@ void main() {
         expect(called, isTrue);
       });
 
-      test('returns child context after run', () {
+      test('returns child context after run', () async {
         final AppContext rootContext = context;
-        rootContext.run(name: 'child', body: () {
+        await rootContext.run<void>(name: 'child', body: () {
           expect(context, isNot(rootContext));
           expect(context.name, 'child');
           called = true;
@@ -42,11 +42,11 @@ void main() {
         expect(called, isTrue);
       });
 
-      test('returns grandchild context after nested run', () {
+      test('returns grandchild context after nested run', () async {
         final AppContext rootContext = context;
-        rootContext.run(name: 'child', body: () {
+        await rootContext.run<void>(name: 'child', body: () async {
           final AppContext childContext = context;
-          childContext.run(name: 'grandchild', body: () {
+          await childContext.run<void>(name: 'grandchild', body: () {
             expect(context, isNot(rootContext));
             expect(context, isNot(childContext));
             expect(context.name, 'grandchild');
@@ -56,9 +56,9 @@ void main() {
         expect(called, isTrue);
       });
 
-      test('scans up zone hierarchy for first context', () {
+      test('scans up zone hierarchy for first context', () async {
         final AppContext rootContext = context;
-        rootContext.run(name: 'child', body: () {
+        await rootContext.run<void>(name: 'child', body: () {
           final AppContext childContext = context;
           runZoned(() {
             expect(context, isNot(rootContext));
@@ -76,7 +76,7 @@ void main() {
         final Completer<void> outer = new Completer<void>();
         final Completer<void> inner = new Completer<void>();
         String value;
-        context.run<void>(
+        await context.run<void>(
           body: () {
             outer.future.then((_) {
               value = context[String];
@@ -93,14 +93,14 @@ void main() {
         expect(value, 'value');
       });
 
-      test('caches generated override values', () {
+      test('caches generated override values', () async {
         int consultationCount = 0;
         String value;
-        context.run(
-          body: () {
+        await context.run<void>(
+          body: () async {
             final StringBuffer buf = new StringBuffer(context[String]);
             buf.write(context[String]);
-            context.run(body: () {
+            await context.run<void>(body: () {
               buf.write(context[String]);
             });
             value = buf.toString();
@@ -116,14 +116,14 @@ void main() {
         expect(consultationCount, 1);
       });
 
-      test('caches generated fallback values', () {
+      test('caches generated fallback values', () async {
         int consultationCount = 0;
         String value;
-        context.run(
-          body: () {
+        await context.run(
+          body: () async {
             final StringBuffer buf = new StringBuffer(context[String]);
             buf.write(context[String]);
-            context.run(body: () {
+            await context.run<void>(body: () {
               buf.write(context[String]);
             });
             value = buf.toString();
@@ -139,8 +139,8 @@ void main() {
         expect(consultationCount, 1);
       });
 
-      test('returns null if generated value is null', () {
-        final String value = context.run(
+      test('returns null if generated value is null', () async {
+        final String value = await context.run<String>(
           body: () => context[String],
           overrides: <Type, Generator>{
             String: () => null,
@@ -150,7 +150,7 @@ void main() {
       });
 
       test('throws if generator has dependency cycle', () async {
-        final Future<String> value = context.run<Future<String>>(
+        final Future<String> value = context.run<String>(
           body: () async {
             return context[String];
           },
@@ -172,13 +172,13 @@ void main() {
 
     group('run', () {
       test('returns the value returned by body', () async {
-        expect(context.run<int>(body: () => 123), 123);
-        expect(context.run<String>(body: () => 'value'), 'value');
+        expect(await context.run<int>(body: () => 123), 123);
+        expect(await context.run<String>(body: () => 'value'), 'value');
         expect(await context.run<Future<int>>(body: () async => 456), 456);
       });
 
-      test('passes name to child context', () {
-        context.run(name: 'child', body: () {
+      test('passes name to child context', () async {
+        await context.run<void>(name: 'child', body: () {
           expect(context.name, 'child');
         });
       });
@@ -190,8 +190,8 @@ void main() {
           called = false;
         });
 
-        test('are applied after parent context is consulted', () {
-          final String value = context.run<String>(
+        test('are applied after parent context is consulted', () async {
+          final String value = await context.run<String>(
             body: () {
               return context.run<String>(
                 body: () {
@@ -208,9 +208,9 @@ void main() {
           expect(value, 'child');
         });
 
-        test('are not applied if parent context supplies value', () {
+        test('are not applied if parent context supplies value', () async {
           bool childConsulted = false;
-          final String value = context.run<String>(
+          final String value = await context.run<String>(
             body: () {
               return context.run<String>(
                 body: () {
@@ -234,8 +234,8 @@ void main() {
           expect(childConsulted, isFalse);
         });
 
-        test('may depend on one another', () {
-          final String value = context.run<String>(
+        test('may depend on one another', () async {
+          final String value = await context.run<String>(
             body: () {
               return context[String];
             },
@@ -249,9 +249,9 @@ void main() {
       });
 
       group('overrides', () {
-        test('intercept consultation of parent context', () {
+        test('intercept consultation of parent context', () async {
           bool parentConsulted = false;
-          final String value = context.run<String>(
+          final String value = await context.run<String>(
             body: () {
               return context.run<String>(
                 body: () => context[String],

packages/flutter_tools/test/src/context.dart

@@ -59,7 +59,7 @@ void testUsingContext(String description, dynamic testMethod(), {
 
   test(description, () async {
     await runInContext<dynamic>(() {
-      return context.run<Future<dynamic>>(
+      return context.run<dynamic>(
         name: 'mocks',
         overrides: <Type, Generator>{
           Config: () => buildConfig(fs),
@@ -84,7 +84,7 @@ void testUsingContext(String description, dynamic testMethod(), {
 
           return runZoned(() {
             try {
-              return context.run<Future<dynamic>>(
+              return context.run<dynamic>(
                 // Apply the overrides to the test context in the zone since their
                 // instantiation may reference items already stored on the context.
                 overrides: overrides,