error handling when path to dir provided instead of file (#109796)

packages/flutter_tools/lib/executable.dart

@@ -194,7 +194,7 @@ List<FlutterCommand> generateCommands({
     featureFlags: featureFlags,
   ),
   RunCommand(verboseHelp: verboseHelp),
-  ScreenshotCommand(),
+  ScreenshotCommand(fs: globals.fs),
   ShellCompletionCommand(),
   TestCommand(verboseHelp: verboseHelp, verbose: verbose),
   UpgradeCommand(verboseHelp: verboseHelp),

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

@@ -20,7 +20,7 @@ const String _kSkiaType = 'skia';
 const String _kRasterizerType = 'rasterizer';
 
 class ScreenshotCommand extends FlutterCommand {
-  ScreenshotCommand() {
+  ScreenshotCommand({required this.fs}) {
     argParser.addOption(
       _kOut,
       abbr: 'o',
@@ -53,6 +53,8 @@ class ScreenshotCommand extends FlutterCommand {
     usesDeviceTimeoutOption();
   }
 
+  final FileSystem fs;
+
   @override
   String get name => 'screenshot';
 
@@ -101,7 +103,7 @@ class ScreenshotCommand extends FlutterCommand {
   Future<FlutterCommandResult> runCommand() async {
     File? outputFile;
     if (argResults?.wasParsed(_kOut) ?? false) {
-      outputFile = globals.fs.file(stringArgDeprecated(_kOut));
+      outputFile = fs.file(stringArgDeprecated(_kOut));
     }
 
     bool success = true;
@@ -123,16 +125,27 @@ class ScreenshotCommand extends FlutterCommand {
 
   Future<void> runScreenshot(File? outputFile) async {
     outputFile ??= globals.fsUtils.getUniqueFile(
-      globals.fs.currentDirectory,
+      fs.currentDirectory,
       'flutter',
       'png',
     );
+
     try {
       await device!.takeScreenshot(outputFile);
     } on Exception catch (error) {
       throwToolExit('Error taking screenshot: $error');
     }
+
+    checkOutput(outputFile, fs);
+
+    try {
       _showOutputFileInfo(outputFile);
+    } on Exception catch (error) {
+      throwToolExit(
+        'Error with provided file path: "${outputFile.path}"\n'
+        'Error: $error'
+      );
+    }
   }
 
   Future<bool> runSkia(File? outputFile) async {
@@ -147,7 +160,7 @@ class ScreenshotCommand extends FlutterCommand {
       return false;
     }
     outputFile ??= globals.fsUtils.getUniqueFile(
-      globals.fs.currentDirectory,
+      fs.currentDirectory,
       'flutter',
       'skp',
     );
@@ -171,7 +184,7 @@ class ScreenshotCommand extends FlutterCommand {
       return false;
     }
     outputFile ??= globals.fsUtils.getUniqueFile(
-      globals.fs.currentDirectory,
+      fs.currentDirectory,
       'flutter',
       'png',
     );
@@ -183,6 +196,15 @@ class ScreenshotCommand extends FlutterCommand {
     return true;
   }
 
+  static void checkOutput(File outputFile, FileSystem fs) {
+    if (!fs.file(outputFile.path).existsSync()) {
+      throwToolExit(
+          'File was not created, ensure path is valid\n'
+          'Path provided: "${outputFile.path}"'
+      );
+    }
+  }
+
   void _ensureOutputIsNotJsonRpcError(File outputFile) {
     if (outputFile.lengthSync() >= 1000) {
       return;
@@ -197,6 +219,6 @@ class ScreenshotCommand extends FlutterCommand {
 
   void _showOutputFileInfo(File outputFile) {
     final int sizeKB = (outputFile.lengthSync()) ~/ 1024;
-    globals.printStatus('Screenshot written to ${globals.fs.path.relative(outputFile.path)} (${sizeKB}kB).');
+    globals.printStatus('Screenshot written to ${fs.path.relative(outputFile.path)} (${sizeKB}kB).');
   }
 }

packages/flutter_tools/test/commands.shard/hermetic/screenshot_command_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/cache.dart';
@@ -26,12 +27,12 @@ void main() {
         throw Exception('dummy');
       };
 
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot', '--type=skia', '--observatory-url=http://localhost:8181']),
         throwsA(isException.having((Exception exception) => exception.toString(), 'message', contains('dummy'))),
       );
 
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot', '--type=rasterizer', '--observatory-url=http://localhost:8181']),
         throwsA(isException.having((Exception exception) => exception.toString(), 'message', contains('dummy'))),
       );
@@ -39,29 +40,70 @@ void main() {
 
 
     testUsingContext('rasterizer and skia screenshots require observatory uri', () async {
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot', '--type=skia']),
         throwsToolExit(message: 'Observatory URI must be specified for screenshot type skia')
       );
 
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot', '--type=rasterizer',]),
         throwsToolExit(message: 'Observatory URI must be specified for screenshot type rasterizer'),
       );
     });
 
     testUsingContext('device screenshots require device', () async {
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot']),
         throwsToolExit(message: 'Must have a connected device for screenshot type device'),
       );
     });
 
     testUsingContext('device screenshots cannot provided Observatory', () async {
-      await expectLater(() => createTestCommandRunner(ScreenshotCommand())
+      await expectLater(() => createTestCommandRunner(ScreenshotCommand(fs: MemoryFileSystem.test()))
         .run(<String>['screenshot',  '--observatory-url=http://localhost:8181']),
         throwsToolExit(message: 'Observatory URI cannot be provided for screenshot type device'),
       );
     });
   });
+
+  group('Screenshot file validation', () {
+    testWithoutContext('successful in pwd', () async {
+      final MemoryFileSystem fs = MemoryFileSystem.test();
+      fs.file('test.png').createSync();
+      fs.directory('sub_dir').createSync();
+      fs.file('sub_dir/test.png').createSync();
+
+      expect(() => ScreenshotCommand.checkOutput(fs.file('test.png'), fs),
+          returnsNormally);
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('sub_dir/test.png'), fs),
+          returnsNormally);
+    });
+
+    testWithoutContext('failed in pwd', () async {
+      final MemoryFileSystem fs = MemoryFileSystem.test();
+      fs.directory('sub_dir').createSync();
+
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('test.png'), fs),
+          throwsToolExit(
+              message: 'File was not created, ensure path is valid'));
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('../'), fs),
+          throwsToolExit(
+              message: 'File was not created, ensure path is valid'));
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('.'), fs),
+          throwsToolExit(
+              message: 'File was not created, ensure path is valid'));
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('/'), fs),
+          throwsToolExit(
+              message: 'File was not created, ensure path is valid'));
+      expect(
+          () => ScreenshotCommand.checkOutput(fs.file('sub_dir/test.png'), fs),
+          throwsToolExit(
+              message: 'File was not created, ensure path is valid'));
+    });
+  });
 }