Always show diagnostics (#57532)

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

@@ -60,34 +60,39 @@ class DevicesCommand extends FlutterCommand {
 
     if (boolArg('machine')) {
       await printDevicesAsJson(devices);
-    } else if (devices.isEmpty) {
-      final StringBuffer status = StringBuffer('No devices detected.');
-      status.writeln();
-      status.writeln();
-      status.writeln('Run "flutter emulators" to list and start any available device emulators.');
-      status.writeln();
-      status.write('If you expected your device to be detected, please run "flutter doctor" to diagnose potential issues. ');
-      if (timeout == null) {
-        status.write('You may also try increasing the time to wait for connected devices with the --timeout flag. ');
-      }
-      status.write('Visit https://flutter.dev/setup/ for troubleshooting tips.');
-
-      globals.printStatus(status.toString());
-      final List<String> diagnostics = await deviceManager.getDeviceDiagnostics();
-      if (diagnostics.isNotEmpty) {
-        globals.printStatus('');
-        for (final String diagnostic in diagnostics) {
-          globals.printStatus('• $diagnostic', hangingIndent: 2);
+    } else {
+      if (devices.isEmpty) {
+        final StringBuffer status = StringBuffer('No devices detected.');
+        status.writeln();
+        status.writeln();
+        status.writeln('Run "flutter emulators" to list and start any available device emulators.');
+        status.writeln();
+        status.write('If you expected your device to be detected, please run "flutter doctor" to diagnose potential issues. ');
+        if (timeout == null) {
+          status.write('You may also try increasing the time to wait for connected devices with the --timeout flag. ');
         }
+        status.write('Visit https://flutter.dev/setup/ for troubleshooting tips.');
+
+        globals.printStatus(status.toString());
+      } else {
+        globals.printStatus('${devices.length} connected ${pluralize('device', devices.length)}:\n');
+        await Device.printDevices(devices);
       }
-    } else {
-      globals.printStatus('${devices.length} connected ${pluralize('device', devices.length)}:\n');
-      await Device.printDevices(devices);
+      await _printDiagnostics();
     }
-
     return FlutterCommandResult.success();
   }
 
+  Future<void> _printDiagnostics() async {
+    final List<String> diagnostics = await deviceManager.getDeviceDiagnostics();
+    if (diagnostics.isNotEmpty) {
+      globals.printStatus('');
+      for (final String diagnostic in diagnostics) {
+        globals.printStatus('• $diagnostic', hangingIndent: 2);
+      }
+    }
+  }
+
   Future<void> printDevicesAsJson(List<Device> devices) async {
     globals.printStatus(
       const JsonEncoder.withIndent('  ').convert(

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

@@ -84,6 +84,25 @@ void main() {
       DeviceManager: () => _FakeDeviceManager(),
       ProcessManager: () => MockProcessManager(),
     });
+
+    testUsingContext('available devices and diagnostics', () async {
+      final DevicesCommand command = DevicesCommand();
+      await createTestCommandRunner(command).run(<String>['devices']);
+      expect(
+        testLogger.statusText,
+        '''
+2 connected devices:
+
+ephemeral • ephemeral • android-arm    • Test SDK (1.2.3) (emulator)
+webby     • webby     • web-javascript • Web SDK (1.2.4) (emulator)
+
+• Cannot connect to device ABC
+'''
+      );
+    }, overrides: <Type, Generator>{
+      DeviceManager: () => _FakeDeviceManager(),
+      ProcessManager: () => MockProcessManager(),
+    });
   });
 }
 
@@ -126,4 +145,8 @@ class _FakeDeviceManager extends DeviceManager {
   Future<List<Device>> refreshAllConnectedDevices({Duration timeout}) =>
     getAllConnectedDevices();
 
+  @override
+  Future<List<String>> getDeviceDiagnostics() => Future<List<String>>.value(
+    <String>['Cannot connect to device ABC']
+  );
 }