Add validity checks to create (#3215)

* Add validity checks to create

* Adjust indent

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

@@ -88,6 +88,10 @@ class CreateCommand extends Command {
     String dirPath = path.normalize(projectDir.absolute.path);
     String projectName = _normalizeProjectName(path.basename(dirPath));
 
+    if (_validateProjectDir(dirPath) != null) {
+      printError(_validateProjectDir(dirPath));
+      return 1;
+    }
     if (_validateProjectName(projectName) != null) {
       printError(_validateProjectName(projectName));
       return 1;
@@ -217,9 +221,32 @@ final Set<String> _packageDependencies = new Set<String>.from(<String>[
 String _validateProjectName(String projectName) {
   if (_packageDependencies.contains(projectName)) {
     return "Invalid project name: '$projectName' - this will conflict with Flutter "
-    "package dependencies.";
+      "package dependencies.";
   }
+  return null;
+}
 
+/// Return `null` if the project directory is legal. Return a validation message
+/// if we should disallow the directory name.
+String _validateProjectDir(String projectName) {
+  FileSystemEntityType type = FileSystemEntity.typeSync(projectName);
+  if (type != FileSystemEntityType.NOT_FOUND) {
+    switch(type) {
+      case FileSystemEntityType.DIRECTORY:
+        // Do not re-use directory if it is not empty.
+        if (new Directory(projectName).listSync(followLinks: false).isNotEmpty) {
+          return "Invalid project name: '$projectName' - refers to a directory "
+            "that is not empty.";
+        };
+        break;
+      case FileSystemEntityType.FILE:
+        // Do not overwrite files.
+        return "Invalid project name: '$projectName' - file exists.";
+      case FileSystemEntityType.LINK:
+        // Do not overwrite links.
+        return "Invalid project name: '$projectName' - refers to a link.";
+    }
+  }
   return null;
 }
 

packages/flutter_tools/test/create_test.dart

@@ -48,5 +48,31 @@ void main() {
     },
     // This test can take a while due to network requests.
     timeout: new Timeout(new Duration(minutes: 2)));
+
+    // Verify that we fail with an error code when the file exists.
+    testUsingContext('fails when file exists', () async {
+      ArtifactStore.flutterRoot = '../..';
+      CreateCommand command = new CreateCommand();
+      CommandRunner runner = new CommandRunner('test_flutter', '')
+        ..addCommand(command);
+      File existingFile = new File("${temp.path.toString()}/bad");
+      if (!existingFile.existsSync()) existingFile.createSync();
+      await runner.run(['create', existingFile.path])
+          .then((int code) => expect(code, equals(1)));
+    });
+
+    // Verify that we fail with an error code when the file exists.
+    testUsingContext('fails with non-empty directory', () async {
+      ArtifactStore.flutterRoot = '../..';
+      CreateCommand command = new CreateCommand();
+      CommandRunner runner = new CommandRunner('test_flutter', '')
+        ..addCommand(command);
+      File existingFile = new File("${temp.path.toString()}/bad");
+      if (!existingFile.existsSync()) existingFile.createSync();
+      RandomAccessFile raf = existingFile.openSync();
+      raf.close();
+      await runner.run(['create', temp.path])
+          .then((int code) => expect(code, equals(1)));
+    });
   });
 }