symfony
diff --git a/‎src/Symfony/Component/Console/Command/DumpCompletionCommand.php
Lines changed: 22 additions & 4 deletions b/‎src/Symfony/Component/Console/Command/DumpCompletionCommand.php
Lines changed: 22 additions & 4 deletions
diff --git a/‎src/Symfony/Component/Console/Tests/Command/DumpCompletionCommandTest.php
Lines changed: 29 additions & 0 deletions b/‎src/Symfony/Component/Console/Tests/Command/DumpCompletionCommandTest.php
Lines changed: 29 additions & 0 deletions
@@ -11,6 +11,9 @@
 
 namespace Symfony\Component\Console\Command;
 
+use Symfony\Component\Console\Completion\CompletionInput;
+use Symfony\Component\Console\Completion\CompletionInterface;
+use Symfony\Component\Console\Completion\CompletionSuggestions;
 use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
@@ -23,11 +26,18 @@
  *
  * @author Wouter de Jong <wouter@wouterj.nl>
  */
-final class DumpCompletionCommand extends Command
+final class DumpCompletionCommand extends Command implements CompletionInterface
 {
     protected static $defaultName = 'completion';
     protected static $defaultDescription = 'Dump the shell completion script';
 
+    public function complete(CompletionInput $input, CompletionSuggestions $suggestions): void
+    {
+        if ($input->mustSuggestArgumentValuesFor('shell')) {
+            $suggestions->suggestValues($this->getSupportedShells());
+        }
+    }
+
     protected function configure()
     {
         $fullCommand = $_SERVER['PHP_SELF'];
@@ -82,9 +92,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         $shell = $input->getArgument('shell') ?? self::guessShell();
         $completionFile = __DIR__.'/../Resources/completion.'.$shell;
         if (!file_exists($completionFile)) {
-            $supportedShells = array_map(function ($f) {
-                return pathinfo($f, \PATHINFO_EXTENSION);
-            }, glob(__DIR__.'/../Resources/completion.*'));
+            $supportedShells = $this->getSupportedShells();
 
             ($output instanceof ConsoleOutputInterface ? $output->getErrorOutput() : $output)
                 ->writeln(sprintf('<error>Detected shell "%s", which is not supported by Symfony shell completion (supported shells: "%s").</>', $shell, implode('", "', $supportedShells)));
@@ -113,4 +121,14 @@ private function tailDebugLog(string $commandName, OutputInterface $output): voi
             $output->write($line);
         });
     }
+
+    /**
+     * @return string[]
+     */
+    private function getSupportedShells(): array
+    {
+        return array_map(function ($f) {
+            return pathinfo($f, \PATHINFO_EXTENSION);
+        }, glob(__DIR__.'/../Resources/completion.*'));
+    }
 }
@@ -0,0 +1,29 @@
+<?php
+
+namespace Symfony\Component\Console\Tests\Command;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\Command\DumpCompletionCommand;
+use Symfony\Component\Console\Tester\CommandCompletionTester;
+
+class DumpCompletionCommandTest extends TestCase
+{
+    /**
+     * @dataProvider provideCompletionSuggestions
+     */
+    public function testComplete(array $input, array $expectedSuggestions)
+    {
+        $tester = new CommandCompletionTester(new DumpCompletionCommand());
+        $suggestions = $tester->complete($input);
+
+        $this->assertSame($expectedSuggestions, $suggestions);
+    }
+
+    public function provideCompletionSuggestions()
+    {
+        yield 'shell' => [
+            [''],
+            ['bash'],
+        ];
+    }
+}