minor #18664 [Console] Add more examples for lazy commands (theofidry)

This PR was submitted for the 6.4 branch but it was squashed and merged into the 6.3 branch instead.

Discussion
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[Console] Add more examples for lazy commands

I think the current doc is a bit confusing regarding the laziness of commands:

- It does not mention `LazyCommand` which is quite important to make a command lazy in a way it still works with the `list` command which is used a lot.
- The `list` doc regarding instantiating the commands is a bit too absolute. Technically it is not wrong but there is also more subtleties to it. Indeed what it will really do is instantiate the command and then try to get the name and description. Which also means if the underlying command/factory can still not be instantiated (either by tweaking `Command` or using `LazyCommand`). This is unlike another command like the auto-complete or help which will try to get the input definition in which case even a `LazyCommand` will call its command factory.

I am not sure which branch it should target however and I am sure there is a lot to say about the phrasing used.

Commits
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5f063a2 [Console] Add more examples for lazy commands

Author: OskarStark

console/commands_as_services.rst

@@ -133,3 +133,5 @@ only when the ``app:sunshine`` command is actually called.
 .. caution::
 
     Calling the ``list`` command will instantiate all commands, including lazy commands.
+    However, if the command is a ``Symfony\Component\Console\Command\LazyCommand``, then
+    the underlying command factory will not be executed.

console/lazy_commands.rst

@@ -10,6 +10,13 @@ The traditional way of adding commands to your application is to use
 :method:`Symfony\\Component\\Console\\Application::add`, which expects a
 ``Command`` instance as an argument.
 
+This approach can have downsides as some commands might be expensive to
+instantiate in which case you may want to lazy-load them. Note however that lazy-loading
+is not absolute. Indeed a few commands such as `list`, `help` or `_complete` can
+require to instantiate other commands although they are lazy. For example `list` needs
+to get the name and description of all commands, which might require the command to be
+instantiated to get.
+
 In order to lazy-load commands, you need to register an intermediate loader
 which will be responsible for returning ``Command`` instances::
 
@@ -19,7 +26,9 @@ which will be responsible for returning ``Command`` instances::
     use Symfony\Component\Console\CommandLoader\FactoryCommandLoader;
 
     $commandLoader = new FactoryCommandLoader([
-        'app:heavy' => function (): Command { return new HeavyCommand(); },
+        // Note that the `list` command will still instantiate that command
+        // in this example.
+        'app:heavy' => static fn(): Command => new HeavyCommand(),
     ]);
 
     $application = new Application();
@@ -36,6 +45,28 @@ method accepts any
 :class:`Symfony\\Component\\Console\\CommandLoader\\CommandLoaderInterface`
 instance so you can use your own implementation.
 
+Another way to do so is to take advantage of ``Symfony\Component\Console\Command\LazyCommand``::
+
+    use App\Command\HeavyCommand;
+    use Symfony\Component\Console\Application;
+    use Symfony\Component\Console\Command\Command;
+    use Symfony\Component\Console\CommandLoader\FactoryCommandLoader;
+
+    // In this case although the command is instantiated, the underlying command factory
+    // will not be executed unless the command is actually executed or one tries to access
+    // to its input definition to know its argument or option inputs.
+    $lazyCommand = new LazyCommand(
+        'app:heavy',
+        [],
+        'This is another more complete form of lazy command.',
+        false,
+        static fn (): Command => new HeavyCommand(),
+    );
+
+    $application = new Application();
+    $application->add($lazyCommand);
+    $application->run();
+
 Built-in Command Loaders
 ------------------------