feature #22734 [Console] Add support for command lazy-loading (chalasr)

This PR was merged into the 3.4 branch.

Discussion
----------

[Console] Add support for command lazy-loading

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/symfony/issues/12063 https://github.com/symfony/symfony/pull/16438 https://github.com/symfony/symfony/pull/13946 #21781
| License       | MIT
| Doc PR        | todo

This PR adds command lazy-loading support to the console, based on PSR-11 and DI tags.
(https://github.com/symfony/symfony/issues/12063#issuecomment-57173784)

Commands registered as services which set the `command` attribute on their `console.command` tag are now instantiated when calling `Application::get()` instead of all instantiated at `run()`.

__Usage__

```yaml
app.command.heavy:
    tags:
        - { name: console.command, command: app:heavy }
```

This way private command services can be inlined (no public aliases, remain really private).

With console+PSR11 implem only:

```php
$application = new Application();
$container = new ServiceLocator(['heavy' => function () { return new Heavy(); }]);
$application->setCommandLoader(new ContainerCommandLoader($container, ['app:heavy' => 'heavy']);
```

Implementation is widely inspired from Twig runtime loaders (without the definition/runtime separation which is not needed here).

Commits
-------

7f97519 Add support for command lazy-loading

src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md

@@ -18,6 +18,8 @@ CHANGELOG
    `Symfony\Component\Translation\DependencyInjection\TranslationExtractorPass` instead
  * Deprecated `TranslatorPass`, use 
    `Symfony\Component\Translation\DependencyInjection\TranslatorPass` instead
+ * Added `command` attribute to the `console.command` tag which takes the command
+   name as value, using it makes the command lazy
 
 3.3.0
 -----

src/Symfony/Bundle/FrameworkBundle/Console/Application.php

@@ -68,15 +68,7 @@ class Application extends BaseApplication
     {
         $this->kernel->boot();
 
-        $container = $this->kernel->getContainer();
-
-        foreach ($this->all() as $command) {
-            if ($command instanceof ContainerAwareInterface) {
-                $command->setContainer($container);
-            }
-        }
-
-        $this->setDispatcher($container->get('event_dispatcher'));
+        $this->setDispatcher($this->kernel->getContainer()->get('event_dispatcher'));
 
         return parent::doRun($input, $output);
     }
@@ -98,7 +90,13 @@ class Application extends BaseApplication
     {
         $this->registerCommands();
 
-        return parent::get($name);
+        $command = parent::get($name);
+
+        if ($command instanceof ContainerAwareInterface) {
+            $command->setContainer($this->kernel->getContainer());
+        }
+
+        return $command;
     }
 
     /**
@@ -144,9 +142,15 @@ class Application extends BaseApplication
             }
         }
 
+        if ($container->has('console.command_loader')) {
+            $this->setCommandLoader($container->get('console.command_loader'));
+        }
+
         if ($container->hasParameter('console.command.ids')) {
             foreach ($container->getParameter('console.command.ids') as $id) {
-                $this->add($container->get($id));
+                if (false !== $id) {
+                    $this->add($container->get($id));
+                }
             }
         }
     }

src/Symfony/Bundle/FrameworkBundle/Tests/Command/RouterDebugCommandTest.php

@@ -77,10 +77,15 @@ class RouterDebugCommandTest extends TestCase
 
         $container = $this->getMockBuilder('Symfony\Component\DependencyInjection\ContainerInterface')->getMock();
         $container
-            ->expects($this->once())
+            ->expects($this->atLeastOnce())
             ->method('has')
-            ->with('router')
-            ->will($this->returnValue(true))
+            ->will($this->returnCallback(function ($id) {
+                if ('console.command_loader' === $id) {
+                    return false;
+                }
+
+                return true;
+            }))
         ;
         $container
             ->expects($this->any())

src/Symfony/Bundle/FrameworkBundle/Tests/Command/RouterMatchCommandTest.php

@@ -78,8 +78,14 @@ class RouterMatchCommandTest extends TestCase
         $container
             ->expects($this->atLeastOnce())
             ->method('has')
-            ->with('router')
-            ->will($this->returnValue(true));
+            ->will($this->returnCallback(function ($id) {
+                if ('console.command_loader' === $id) {
+                    return false;
+                }
+
+                return true;
+            }))
+        ;
         $container
             ->expects($this->any())
             ->method('get')

src/Symfony/Bundle/FrameworkBundle/composer.json

@@ -35,7 +35,7 @@
         "fig/link-util": "^1.0",
         "symfony/asset": "~3.3|~4.0",
         "symfony/browser-kit": "~2.8|~3.0|~4.0",
-        "symfony/console": "~3.3|~4.0",
+        "symfony/console": "~3.4|~4.0",
         "symfony/css-selector": "~2.8|~3.0|~4.0",
         "symfony/dom-crawler": "~2.8|~3.0|~4.0",
         "symfony/polyfill-intl-icu": "~1.0",
@@ -64,7 +64,7 @@
         "phpdocumentor/type-resolver": "<0.2.0",
         "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0",
         "symfony/asset": "<3.3",
-        "symfony/console": "<3.3",
+        "symfony/console": "<3.4",
         "symfony/form": "<3.3",
         "symfony/property-info": "<3.3",
         "symfony/serializer": "<3.3",

src/Symfony/Bundle/SecurityBundle/Resources/config/console.xml

@@ -10,7 +10,7 @@
         <service id="security.console.user_password_encoder_command" class="Symfony\Bundle\SecurityBundle\Command\UserPasswordEncoderCommand">
             <argument type="service" id="security.encoder_factory"/>
             <argument type="collection" /> <!-- encoders' user classes -->
-            <tag name="console.command" />
+            <tag name="console.command" command="security:encode-password" />
         </service>
     </services>
 </container>

src/Symfony/Bundle/WebServerBundle/Resources/config/webserver.xml

@@ -10,21 +10,21 @@
         <service id="web_server.command.server_run" class="Symfony\Bundle\WebServerBundle\Command\ServerRunCommand">
             <argument>%kernel.project_dir%/web</argument>
             <argument>%kernel.environment%</argument>
-            <tag name="console.command" />
+            <tag name="console.command" command="server:run" />
         </service>
 
         <service id="web_server.command.server_start" class="Symfony\Bundle\WebServerBundle\Command\ServerStartCommand">
             <argument>%kernel.project_dir%/web</argument>
             <argument>%kernel.environment%</argument>
-            <tag name="console.command" />
+            <tag name="console.command" command="server:start" />
         </service>
 
         <service id="web_server.command.server_stop" class="Symfony\Bundle\WebServerBundle\Command\ServerStopCommand">
-            <tag name="console.command" />
+            <tag name="console.command" command="server:stop" />
         </service>
 
         <service id="web_server.command.server_status" class="Symfony\Bundle\WebServerBundle\Command\ServerStatusCommand">
-            <tag name="console.command" />
+            <tag name="console.command" command="server:status" />
         </service>
     </services>
 </container>

src/Symfony/Component/Console/Application.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Console;
 
+use Symfony\Component\Console\CommandLoader\CommandLoaderInterface;
 use Symfony\Component\Console\Exception\ExceptionInterface;
 use Symfony\Component\Console\Formatter\OutputFormatter;
 use Symfony\Component\Console\Helper\DebugFormatterHelper;
@@ -64,6 +65,7 @@ class Application
     private $runningCommand;
     private $name;
     private $version;
+    private $commandLoader;
     private $catchExceptions = true;
     private $autoExit = true;
     private $definition;
@@ -96,6 +98,11 @@ class Application
         $this->dispatcher = $dispatcher;
     }
 
+    public function setCommandLoader(CommandLoaderInterface $commandLoader)
+    {
+        $this->commandLoader = $commandLoader;
+    }
+
     /**
      * Runs the current application.
      *
@@ -431,6 +438,10 @@ class Application
             throw new LogicException(sprintf('Command class "%s" is not correctly initialized. You probably forgot to call the parent constructor.', get_class($command)));
         }
 
+        if (!$command->getName()) {
+            throw new LogicException(sprintf('The command defined in "%s" cannot have an empty name.', get_class($command)));
+        }
+
         $this->commands[$command->getName()] = $command;
 
         foreach ($command->getAliases() as $alias) {
@@ -451,12 +462,16 @@ class Application
      */
     public function get($name)
     {
-        if (!isset($this->commands[$name])) {
+        if (isset($this->commands[$name])) {
+            $command = $this->commands[$name];
+        } elseif ($this->commandLoader && $this->commandLoader->has($name)) {
+            $command = $this->commandLoader->get($name);
+            $command->setName($name);
+            $this->add($command);
+        } else {
             throw new CommandNotFoundException(sprintf('The command "%s" does not exist.', $name));
         }
 
-        $command = $this->commands[$name];
-
         if ($this->wantHelps) {
             $this->wantHelps = false;
 
@@ -478,7 +493,7 @@ class Application
      */
     public function has($name)
     {
-        return isset($this->commands[$name]);
+        return isset($this->commands[$name]) || ($this->commandLoader && $this->commandLoader->has($name));
     }
 
     /**
@@ -555,7 +570,7 @@ class Application
      */
     public function find($name)
     {
-        $allCommands = array_keys($this->commands);
+        $allCommands = $this->commandLoader ? array_merge($this->commandLoader->getNames(), array_keys($this->commands)) : array_keys($this->commands);
         $expr = preg_replace_callback('{([^:]+|)}', function ($matches) { return preg_quote($matches[1]).'[^:]*'; }, $name);
         $commands = preg_grep('{^'.$expr.'}', $allCommands);
 
@@ -581,12 +596,12 @@ class Application
 
         // filter out aliases for commands which are already on the list
         if (count($commands) > 1) {
-            $commandList = $this->commands;
-            $commands = array_filter($commands, function ($nameOrAlias) use ($commandList, $commands) {
-                $commandName = $commandList[$nameOrAlias]->getName();
+            $commandList = $this->commandLoader ? array_merge(array_flip($this->commandLoader->getNames()), $this->commands) : $this->commands;
+            $commands = array_unique(array_filter($commands, function ($nameOrAlias) use ($commandList, $commands) {
+                $commandName = $commandList[$nameOrAlias] instanceof Command ? $commandList[$nameOrAlias]->getName() : $nameOrAlias;
 
                 return $commandName === $nameOrAlias || !in_array($commandName, $commands);
-            });
+            }));
         }
 
         $exact = in_array($name, $commands, true);
@@ -598,6 +613,9 @@ class Application
                 $maxLen = max(Helper::strlen($abbrev), $maxLen);
             }
             $abbrevs = array_map(function ($cmd) use ($commandList, $usableWidth, $maxLen) {
+                if (!$commandList[$cmd] instanceof Command) {
+                    return $cmd;
+                }
                 $abbrev = str_pad($cmd, $maxLen, ' ').' '.$commandList[$cmd]->getDescription();
 
                 return Helper::strlen($abbrev) > $usableWidth ? Helper::substr($abbrev, 0, $usableWidth - 3).'...' : $abbrev;
@@ -622,7 +640,18 @@ class Application
     public function all($namespace = null)
     {
         if (null === $namespace) {
-            return $this->commands;
+            if (!$this->commandLoader) {
+                return $this->commands;
+            }
+
+            $commands = $this->commands;
+            foreach ($this->commandLoader->getNames() as $name) {
+                if (!isset($commands[$name])) {
+                    $commands[$name] = $this->commandLoader->get($name);
+                }
+            }
+
+            return $commands;
         }
 
         $commands = array();
@@ -632,6 +661,14 @@ class Application
             }
         }
 
+        if ($this->commandLoader) {
+            foreach ($this->commandLoader->getNames() as $name) {
+                if (!isset($commands[$name]) && $namespace === $this->extractNamespace($name, substr_count($namespace, ':') + 1)) {
+                    $commands[$name] = $this->commandLoader->get($name);
+                }
+            }
+        }
+
         return $commands;
     }
 

src/Symfony/Component/Console/CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+3.4.0
+-----
+
+ * added `CommandLoaderInterface` and PSR-11 `ContainerCommandLoader`
+
 3.3.0
 -----
 

src/Symfony/Component/Console/Command/Command.php

@@ -61,10 +61,6 @@ class Command
         }
 
         $this->configure();
-
-        if (!$this->name) {
-            throw new LogicException(sprintf('The command defined in "%s" cannot have an empty name.', get_class($this)));
-        }
     }
 
     /**

src/Symfony/Component/Console/CommandLoader/CommandLoaderInterface.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Symfony\Component\Console\CommandLoader;
+
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Exception\CommandNotFoundException;
+
+/**
+ * @author Robin Chalas <robin.chalas@gmail.com>
+ */
+interface CommandLoaderInterface
+{
+    /**
+     * Loads a command.
+     *
+     * @param string $name
+     *
+     * @return Command
+     *
+     * @throws CommandNotFoundException
+     */
+    public function get($name);
+
+    /**
+     * Checks if a command exists.
+     *
+     * @param string $name
+     *
+     * @return bool
+     */
+    public function has($name);
+
+    /**
+     * @return string[] All registered command names
+     */
+    public function getNames();
+}

src/Symfony/Component/Console/CommandLoader/ContainerCommandLoader.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Symfony\Component\Console\CommandLoader;
+
+use Psr\Container\ContainerInterface;
+use Symfony\Component\Console\Exception\CommandNotFoundException;
+
+/**
+ * Loads commands from a PSR-11 container.
+ *
+ * @author Robin Chalas <robin.chalas@gmail.com>
+ */
+class ContainerCommandLoader implements CommandLoaderInterface
+{
+    private $container;
+    private $commandMap;
+
+    /**
+     * @param ContainerInterface $container  A container from which to load command services
+     * @param array              $commandMap An array with command names as keys and service ids as values
+     */
+    public function __construct(ContainerInterface $container, array $commandMap)
+    {
+        $this->container = $container;
+        $this->commandMap = $commandMap;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($name)
+    {
+        if (!$this->has($name)) {
+            throw new CommandNotFoundException(sprintf('Command "%s" does not exist.', $name));
+        }
+
+        return $this->container->get($this->commandMap[$name]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function has($name)
+    {
+        return isset($this->commandMap[$name]) && $this->container->has($this->commandMap[$name]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getNames()
+    {
+        return array_keys($this->commandMap);
+    }
+}

src/Symfony/Component/Console/DependencyInjection/AddConsoleCommandPass.php

@@ -12,9 +12,12 @@
 namespace Symfony\Component\Console\DependencyInjection;
 
 use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\CommandLoader\ContainerCommandLoader;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\Compiler\ServiceLocatorTagPass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\TypedReference;
 
 /**
  * Registers console commands.
@@ -23,9 +26,20 @@ use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
  */
 class AddConsoleCommandPass implements CompilerPassInterface
 {
+    private $commandLoaderServiceId;
+    private $commandTag;
+
+    public function __construct($commandLoaderServiceId = 'console.command_loader', $commandTag = 'console.command')
+    {
+        $this->commandLoaderServiceId = $commandLoaderServiceId;
+        $this->commandTag = $commandTag;
+    }
+
     public function process(ContainerBuilder $container)
     {
-        $commandServices = $container->findTaggedServiceIds('console.command', true);
+        $commandServices = $container->findTaggedServiceIds($this->commandTag, true);
+        $lazyCommandMap = array();
+        $lazyCommandRefs = array();
         $serviceIds = array();
 
         foreach ($commandServices as $id => $tags) {
@@ -36,21 +50,52 @@ class AddConsoleCommandPass implements CompilerPassInterface
                 throw new InvalidArgumentException(sprintf('Class "%s" used for service "%s" cannot be found.', $class, $id));
             }
             if (!$r->isSubclassOf(Command::class)) {
-                throw new InvalidArgumentException(sprintf('The service "%s" tagged "console.command" must be a subclass of "%s".', $id, Command::class));
+                throw new InvalidArgumentException(sprintf('The service "%s" tagged "%s" must be a subclass of "%s".', $id, $this->commandTag, Command::class));
             }
 
             $commandId = 'console.command.'.strtolower(str_replace('\\', '_', $class));
-            if ($container->hasAlias($commandId) || isset($serviceIds[$commandId])) {
-                $commandId = $commandId.'_'.$id;
-            }
-            if (!$definition->isPublic()) {
-                $container->setAlias($commandId, $id);
-                $id = $commandId;
+
+            if (!isset($tags[0]['command'])) {
+                if (isset($serviceIds[$commandId]) || $container->hasAlias($commandId)) {
+                    $commandId = $commandId.'_'.$id;
+                }
+                if (!$definition->isPublic()) {
+                    $container->setAlias($commandId, $id);
+                    $id = $commandId;
+                }
+                $serviceIds[$commandId] = $id;
+
+                continue;
             }
 
-            $serviceIds[$commandId] = $id;
+            $serviceIds[$commandId] = false;
+            $commandName = $tags[0]['command'];
+            $lazyCommandMap[$commandName] = $id;
+            $lazyCommandRefs[$id] = new TypedReference($id, $class);
+            $aliases = array();
+
+            foreach ($tags as $tag) {
+                if (!isset($tag['command'])) {
+                    throw new InvalidArgumentException(sprintf('Missing "command" attribute on tag "%s" for service "%s".', $this->commandTag, $id));
+                }
+                if ($commandName !== $tag['command']) {
+                    throw new InvalidArgumentException(sprintf('The "command" attribute must be the same on each "%s" tag for service "%s".', $this->commandTag, $id));
+                }
+                if (isset($tag['alias'])) {
+                    $aliases[] = $tag['alias'];
+                    $lazyCommandMap[$tag['alias']] = $id;
+                }
+            }
+
+            if ($aliases) {
+                $definition->addMethodCall('setAliases', array($aliases));
+            }
         }
 
+        $container
+            ->register($this->commandLoaderServiceId, ContainerCommandLoader::class)
+            ->setArguments(array(ServiceLocatorTagPass::register($container, $lazyCommandRefs), $lazyCommandMap));
+
         $container->setParameter('console.command.ids', $serviceIds);
     }
 }

src/Symfony/Component/Console/Tests/ApplicationTest.php

@@ -13,6 +13,9 @@ namespace Symfony\Component\Console\Tests;
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Console\Application;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\CommandLoader\ContainerCommandLoader;
+use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass;
 use Symfony\Component\Console\Helper\HelperSet;
 use Symfony\Component\Console\Helper\FormatterHelper;
 use Symfony\Component\Console\Input\ArgvInput;
@@ -31,6 +34,8 @@ use Symfony\Component\Console\Event\ConsoleErrorEvent;
 use Symfony\Component\Console\Event\ConsoleExceptionEvent;
 use Symfony\Component\Console\Event\ConsoleTerminateEvent;
 use Symfony\Component\Console\Exception\CommandNotFoundException;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\ServiceLocator;
 use Symfony\Component\EventDispatcher\EventDispatcher;
 
 class ApplicationTest extends TestCase
@@ -114,6 +119,26 @@ class ApplicationTest extends TestCase
         $this->assertCount(1, $commands, '->all() takes a namespace as its first argument');
     }
 
+    public function testAllWithCommandLoader()
+    {
+        $application = new Application();
+        $commands = $application->all();
+        $this->assertInstanceOf('Symfony\\Component\\Console\\Command\\HelpCommand', $commands['help'], '->all() returns the registered commands');
+
+        $application->add(new \FooCommand());
+        $commands = $application->all('foo');
+        $this->assertCount(1, $commands, '->all() takes a namespace as its first argument');
+
+        $application->setCommandLoader(new ContainerCommandLoader(
+            new ServiceLocator(array('foo-bar' => function () { return new \Foo1Command(); })),
+            array('foo:bar1' => 'foo-bar')
+        ));
+        $commands = $application->all('foo');
+        $this->assertCount(2, $commands, '->all() takes a namespace as its first argument');
+        $this->assertInstanceOf(\FooCommand::class, $commands['foo:bar'], '->all() returns the registered commands');
+        $this->assertInstanceOf(\Foo1Command::class, $commands['foo:bar1'], '->all() returns the registered commands');
+    }
+
     public function testRegister()
     {
         $application = new Application();
@@ -166,6 +191,30 @@ class ApplicationTest extends TestCase
         $this->assertInstanceOf('Symfony\Component\Console\Command\HelpCommand', $command, '->get() returns the help command if --help is provided as the input');
     }
 
+    public function testHasGetWithCommandLoader()
+    {
+        $application = new Application();
+        $this->assertTrue($application->has('list'), '->has() returns true if a named command is registered');
+        $this->assertFalse($application->has('afoobar'), '->has() returns false if a named command is not registered');
+
+        $application->add($foo = new \FooCommand());
+        $this->assertTrue($application->has('afoobar'), '->has() returns true if an alias is registered');
+        $this->assertEquals($foo, $application->get('foo:bar'), '->get() returns a command by name');
+        $this->assertEquals($foo, $application->get('afoobar'), '->get() returns a command by alias');
+
+        $application->setCommandLoader(new ContainerCommandLoader(new ServiceLocator(array(
+            'foo-bar' => function () { return new \Foo1Command(); },
+        )), array('foo:bar1' => 'foo-bar', 'afoobar1' => 'foo-bar')));
+
+        $this->assertTrue($application->has('afoobar'), '->has() returns true if an instance is registered for an alias even with command loader');
+        $this->assertEquals($foo, $application->get('foo:bar'), '->get() returns an instance by name even with command loader');
+        $this->assertEquals($foo, $application->get('afoobar'), '->get() returns an instance by alias even with command loader');
+        $this->assertTrue($application->has('foo:bar1'), '->has() returns true for commands registered in the loader');
+        $this->assertInstanceOf(\Foo1Command::class, $foo1 = $application->get('foo:bar1'), '->get() returns a command by name from the command loader');
+        $this->assertTrue($application->has('afoobar1'), '->has() returns true for commands registered in the loader');
+        $this->assertEquals($foo1, $application->get('afoobar1'), '->get() returns a command by name from the command loader');
+    }
+
     public function testSilentHelp()
     {
         $application = new Application();
@@ -269,6 +318,20 @@ class ApplicationTest extends TestCase
         $this->assertInstanceOf('FooCommand', $application->find('a'), '->find() returns a command if the abbreviation exists for an alias');
     }
 
+    public function testFindWithCommandLoader()
+    {
+        $application = new Application();
+        $application->setCommandLoader(new ContainerCommandLoader(new ServiceLocator(array(
+            'foo-bar' => $f = function () { return new \FooCommand(); },
+        )), array('foo:bar' => 'foo-bar')));
+
+        $this->assertInstanceOf('FooCommand', $application->find('foo:bar'), '->find() returns a command if its name exists');
+        $this->assertInstanceOf('Symfony\Component\Console\Command\HelpCommand', $application->find('h'), '->find() returns a command if its name exists');
+        $this->assertInstanceOf('FooCommand', $application->find('f:bar'), '->find() returns a command if the abbreviation for the namespace exists');
+        $this->assertInstanceOf('FooCommand', $application->find('f:b'), '->find() returns a command if the abbreviation for the namespace and the command name exist');
+        $this->assertInstanceOf('FooCommand', $application->find('a'), '->find() returns a command if the abbreviation exists for an alias');
+    }
+
     /**
      * @dataProvider provideAmbiguousAbbreviations
      */
@@ -1362,6 +1425,35 @@ class ApplicationTest extends TestCase
         $this->assertEquals($tester->getInput()->isInteractive(), @posix_isatty($inputStream));
     }
 
+    public function testRunLazyCommandService()
+    {
+        $container = new ContainerBuilder();
+        $container->addCompilerPass(new AddConsoleCommandPass());
+        $container
+            ->register('lazy-command', LazyCommand::class)
+            ->addTag('console.command', array('command' => 'lazy:command', 'alias' => 'lazy:alias'))
+            ->addTag('console.command', array('command' => 'lazy:command', 'alias' => 'lazy:alias2'));
+        $container->compile();
+
+        $application = new Application();
+        $application->setCommandLoader($container->get('console.command_loader'));
+        $application->setAutoExit(false);
+
+        $tester = new ApplicationTester($application);
+
+        $tester->run(array('command' => 'lazy:command'));
+        $this->assertSame("lazy-command called\n", $tester->getDisplay(true));
+
+        $tester->run(array('command' => 'lazy:alias'));
+        $this->assertSame("lazy-command called\n", $tester->getDisplay(true));
+
+        $tester->run(array('command' => 'lazy:alias2'));
+        $this->assertSame("lazy-command called\n", $tester->getDisplay(true));
+
+        $command = $application->get('lazy:command');
+        $this->assertSame(array('lazy:alias', 'lazy:alias2'), $command->getAliases());
+    }
+
     protected function getDispatcher($skipCommand = false)
     {
         $dispatcher = new EventDispatcher();
@@ -1449,3 +1541,11 @@ class CustomDefaultCommandApplication extends Application
         $this->setDefaultCommand($command->getName());
     }
 }
+
+class LazyCommand extends Command
+{
+    public function execute(InputInterface $input, OutputInterface $output)
+    {
+        $output->writeln('lazy-command called');
+    }
+}

src/Symfony/Component/Console/Tests/Command/CommandTest.php

@@ -46,7 +46,7 @@ class CommandTest extends TestCase
      */
     public function testCommandNameCannotBeEmpty()
     {
-        new Command();
+        (new Application())->add(new Command());
     }
 
     public function testSetApplication()

src/Symfony/Component/Console/Tests/CommandLoader/ContainerCommandLoaderTest.php

@@ -0,0 +1,61 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Console\Tests\CommandLoader;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\CommandLoader\ContainerCommandLoader;
+use Symfony\Component\DependencyInjection\ServiceLocator;
+
+class ContainerCommandLoaderTest extends TestCase
+{
+    public function testHas()
+    {
+        $loader = new ContainerCommandLoader(new ServiceLocator(array(
+            'foo-service' => function () { return new Command('foo'); },
+            'bar-service' => function () { return new Command('bar'); },
+        )), array('foo' => 'foo-service', 'bar' => 'bar-service'));
+
+        $this->assertTrue($loader->has('foo'));
+        $this->assertTrue($loader->has('bar'));
+        $this->assertFalse($loader->has('baz'));
+    }
+
+    public function testGet()
+    {
+        $loader = new ContainerCommandLoader(new ServiceLocator(array(
+            'foo-service' => function () { return new Command('foo'); },
+            'bar-service' => function () { return new Command('bar'); },
+        )), array('foo' => 'foo-service', 'bar' => 'bar-service'));
+
+        $this->assertInstanceOf(Command::class, $loader->get('foo'));
+        $this->assertInstanceOf(Command::class, $loader->get('bar'));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Console\Exception\CommandNotFoundException
+     */
+    public function testGetUnknownCommandThrows()
+    {
+        (new ContainerCommandLoader(new ServiceLocator(array()), array()))->get('unknown');
+    }
+
+    public function testGetCommandNames()
+    {
+        $loader = new ContainerCommandLoader(new ServiceLocator(array(
+            'foo-service' => function () { return new Command('foo'); },
+            'bar-service' => function () { return new Command('bar'); },
+        )), array('foo' => 'foo-service', 'bar' => 'bar-service'));
+
+        $this->assertSame(array('foo', 'bar'), $loader->getNames());
+    }
+}

src/Symfony/Component/Console/Tests/DependencyInjection/AddConsoleCommandPassTest.php

@@ -12,10 +12,13 @@
 namespace Symfony\Component\Console\Tests\DependencyInjection;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\CommandLoader\ContainerCommandLoader;
 use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass;
 use Symfony\Component\Console\Command\Command;
+use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\TypedReference;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 
 class AddConsoleCommandPassTest extends TestCase
@@ -53,6 +56,26 @@ class AddConsoleCommandPassTest extends TestCase
         $this->assertSame(array($alias => $id), $container->getParameter('console.command.ids'));
     }
 
+    public function testProcessRegisterLazyCommands()
+    {
+        $container = new ContainerBuilder();
+        $container
+            ->register('my-command', MyCommand::class)
+            ->setPublic(false)
+            ->addTag('console.command', array('command' => 'my:command', 'alias' => 'my:alias'))
+        ;
+
+        (new AddConsoleCommandPass())->process($container);
+
+        $commandLoader = $container->getDefinition('console.command_loader');
+        $commandLocator = $container->getDefinition((string) $commandLoader->getArgument(0));
+
+        $this->assertSame(ContainerCommandLoader::class, $commandLoader->getClass());
+        $this->assertSame(array('my:command' => 'my-command', 'my:alias' => 'my-command'), $commandLoader->getArgument(1));
+        $this->assertEquals(array(array('my-command' => new ServiceClosureArgument(new TypedReference('my-command', MyCommand::class)))), $commandLocator->getArguments());
+        $this->assertSame(array('console.command.symfony_component_console_tests_dependencyinjection_mycommand' => false), $container->getParameter('console.command.ids'));
+    }
+
     public function visibilityProvider()
     {
         return array(
@@ -72,7 +95,7 @@ class AddConsoleCommandPassTest extends TestCase
         $container->addCompilerPass(new AddConsoleCommandPass());
 
         $definition = new Definition('Symfony\Component\Console\Tests\DependencyInjection\MyCommand');
-        $definition->addTag('console.command');
+        $definition->addTag('console.command', array('command' => 'my:command'));
         $definition->setAbstract(true);
         $container->setDefinition('my-command', $definition);
 
@@ -90,7 +113,7 @@ class AddConsoleCommandPassTest extends TestCase
         $container->addCompilerPass(new AddConsoleCommandPass());
 
         $definition = new Definition('SplObjectStorage');
-        $definition->addTag('console.command');
+        $definition->addTag('console.command', array('command' => 'my:command'));
         $container->setDefinition('my-command', $definition);
 
         $container->compile();