Fail tests with an actionable message when FLUTTER_ROOT is not set (#8236)

Also: Fix some analyzer warnings.

packages/flutter_tools/lib/src/android/android_sdk.dart

@@ -140,7 +140,7 @@ class AndroidSdk {
     if (platformsDir.existsSync()) {
       platforms = platformsDir
         .listSync()
-        .map((FileSystemEntity entity) => fs.path.basename(entity.path))
+        .map<String>((FileSystemEntity entity) => fs.path.basename(entity.path))
         .where((String name) => name.startsWith('android-'))
         .toList();
     }

packages/flutter_tools/lib/src/asset.dart

@@ -336,8 +336,9 @@ Map<_Asset, List<_Asset>> _parseAssets(
   if (manifestDescriptor == null)
     return result;
 
-  excludeDirs = excludeDirs.map(
-    (String exclude) => fs.path.absolute(exclude) + fs.path.separator).toList();
+  excludeDirs = excludeDirs.map<String>(
+    (String exclude) => fs.path.absolute(exclude) + fs.path.separator
+  ).toList();
 
   if (manifestDescriptor.containsKey('assets')) {
     for (String asset in manifestDescriptor['assets']) {

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

@@ -172,7 +172,7 @@ class TestCommand extends FlutterCommand {
     testArgs.add('--');
 
     Directory testDir;
-    Iterable<String> files = argResults.rest.map((String testPath) => fs.path.absolute(testPath)).toList();
+    Iterable<String> files = argResults.rest.map<String>((String testPath) => fs.path.absolute(testPath)).toList();
     if (argResults['start-paused']) {
       if (files.length != 1)
         throwToolExit('When using --start-paused, you must specify a single test file to run.', exitCode: 1);

packages/flutter_tools/test/all.dart

@@ -30,8 +30,7 @@ import 'device_test.dart' as device_test;
 import 'devices_test.dart' as devices_test;
 import 'doctor_test.dart' as doctor_test;
 import 'drive_test.dart' as drive_test;
-import 'forbid_dart_io_test.dart' as forbid_dart_io_test;
-import 'forbid_package_path_test.dart' as forbid_package_path_test;
+import 'forbidden_imports_test.dart' as forbidden_imports_test;
 import 'format_test.dart' as format_test;
 import 'hot_test.dart' as hot_test;
 import 'install_test.dart' as install_test;
@@ -70,8 +69,7 @@ void main() {
   devices_test.main();
   doctor_test.main();
   drive_test.main();
-  forbid_dart_io_test.main();
-  forbid_package_path_test.main();
+  forbidden_imports_test.main();
   format_test.main();
   hot_test.main();
   install_test.main();

packages/flutter_tools/test/forbid_package_path_test.dart

-// Copyright 2016 The Chromium Authors. 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:flutter_tools/src/base/file_system.dart';
-import 'package:flutter_tools/src/base/platform.dart';
-import 'package:test/test.dart';
-
-void main() {
-  setUp(() {
-    String flutterTools = fs.path.join(platform.environment['FLUTTER_ROOT'],
-        'packages', 'flutter_tools');
-    assert(fs.path.equals(fs.currentDirectory.path, flutterTools));
-  });
-
-  test('no unauthorized imports of package:path', () {
-    for (String path in <String>['lib', 'bin', 'test']) {
-      fs.directory(path)
-        .listSync(recursive: true)
-        .where(_isDartFile)
-        .map(_asFile)
-        .forEach((File file) {
-          for (String line in file.readAsLinesSync()) {
-            if (line.startsWith(new RegExp('import.*package:path/path.dart'))) {
-              fail("${file.path} imports 'package:path/path.dart'; use 'fs.path' instead");
-            }
-          }
-        }
-      );
-    }
-  });
-}
-
-bool _isDartFile(FileSystemEntity entity) => entity is File && entity.path.endsWith('.dart');
-
-File _asFile(FileSystemEntity entity) => entity;

packages/flutter_tools/test/forbid_dart_io_test.dart → packages/flutter_tools/test/forbidden_imports_test.dart

@@ -8,12 +8,16 @@ import 'package:test/test.dart';
 
 void main() {
   setUp(() {
-    String flutterTools = fs.path.join(platform.environment['FLUTTER_ROOT'],
-        'packages', 'flutter_tools');
+    String flutterRoot = platform.environment['FLUTTER_ROOT'];
+    if (flutterRoot == null)
+      throw new Exception('Please set FLUTTER_ROOT env var before running tests.');
+    String flutterTools = fs.path.join(flutterRoot, 'packages', 'flutter_tools');
     assert(fs.path.equals(fs.currentDirectory.path, flutterTools));
   });
 
   test('no unauthorized imports of dart:io', () {
+    bool _isNotWhitelisted(FileSystemEntity entity) => entity.path != fs.path.join('lib', 'src', 'base', 'io.dart');
+
     for (String path in <String>['lib', 'bin']) {
       fs.directory(path)
         .listSync(recursive: true)
@@ -31,12 +35,25 @@ void main() {
       );
     }
   });
-}
 
-bool _isDartFile(FileSystemEntity entity) =>
-    entity is File && entity.path.endsWith('.dart');
+  test('no unauthorized imports of package:path', () {
+    for (String path in <String>['lib', 'bin', 'test']) {
+      fs.directory(path)
+          .listSync(recursive: true)
+          .where(_isDartFile)
+          .map(_asFile)
+          .forEach((File file) {
+        for (String line in file.readAsLinesSync()) {
+          if (line.startsWith(new RegExp('import.*package:path/path.dart'))) {
+            fail("${file.path} imports 'package:path/path.dart'; use 'fs.path' instead");
+          }
+        }
+      }
+      );
+    }
+  });
+}
 
-bool _isNotWhitelisted(FileSystemEntity entity) =>
-    entity.path != fs.path.join('lib', 'src', 'base', 'io.dart');
+bool _isDartFile(FileSystemEntity entity) => entity is File && entity.path.endsWith('.dart');
 
 File _asFile(FileSystemEntity entity) => entity;