feature #23510 [Console] Add a factory command loader for standalone application with lazy-loading needs (ogizanagi)

This PR was merged into the 3.4 branch.

Discussion
----------

[Console] Add a factory command loader for standalone application with lazy-loading needs

| Q             | A
| ------------- | ---
| Branch?       | 3.4 <!-- see comment below -->
| Bug fix?      | no
| New feature?  | yes <!-- don't forget updating src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget updating UPGRADE-*.md files -->
| Tests pass?   | yes (failure unrelated)
| Fixed tickets | https://github.com/symfony/symfony/pull/22734#issuecomment-314706630 <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | todo (with https://github.com/symfony/symfony-docs/issues/8147)

So standalone applications can also benefit from the lazy loading feature without requiring a PSR-11 implementation specifically for this need.

The loader does not memoize any resolved command from factories, as it's the `Application` responsibility and the `ContainerCommandLoader` does not either (the PSR-11 does not enforce two successive calls to return the same value).

Commits
-------

9b40b4a [Console] Add a factory command loader for standalone application with lazy-loading needs

src/Symfony/Component/Console/CHANGELOG.md

@@ -4,7 +4,8 @@ CHANGELOG
 3.4.0
 -----
 
- * added `CommandLoaderInterface` and PSR-11 `ContainerCommandLoader`
+ * added `CommandLoaderInterface`, `FactoryCommandLoader` and PSR-11
+   `ContainerCommandLoader` for commands lazy-loading
 
 3.3.0
 -----

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

@@ -0,0 +1,62 @@
+<?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\CommandLoader;
+
+use Symfony\Component\Console\Exception\CommandNotFoundException;
+
+/**
+ * A simple command loader using factories to instantiate commands lazily.
+ *
+ * @author Maxime Steinhausser <maxime.steinhausser@gmail.com>
+ */
+class FactoryCommandLoader implements CommandLoaderInterface
+{
+    private $factories;
+
+    /**
+     * @param callable[] $factories Indexed by command names
+     */
+    public function __construct(array $factories)
+    {
+        $this->factories = $factories;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function has($name)
+    {
+        return isset($this->factories[$name]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($name)
+    {
+        if (!isset($this->factories[$name])) {
+            throw new CommandNotFoundException(sprintf('Command "%s" does not exist.', $name));
+        }
+
+        $factory = $this->factories[$name];
+
+        return $factory();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getNames()
+    {
+        return array_keys($this->factories);
+    }
+}

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

@@ -14,7 +14,7 @@ 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\CommandLoader\FactoryCommandLoader;
 use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass;
 use Symfony\Component\Console\Helper\HelperSet;
 use Symfony\Component\Console\Helper\FormatterHelper;
@@ -35,7 +35,6 @@ 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
@@ -129,10 +128,9 @@ class ApplicationTest extends TestCase
         $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')
-        ));
+        $application->setCommandLoader(new FactoryCommandLoader(array(
+            'foo:bar1' => function () { return new \Foo1Command(); },
+        )));
         $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');
@@ -202,9 +200,9 @@ class ApplicationTest extends TestCase
         $this->assertEquals($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')));
+        $application->setCommandLoader(new FactoryCommandLoader(array(
+            'foo:bar1' => function () { return new \Foo1Command(); },
+        )));
 
         $this->assertTrue($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');
@@ -321,9 +319,9 @@ class ApplicationTest extends TestCase
     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')));
+        $application->setCommandLoader(new FactoryCommandLoader(array(
+            'foo:bar' => $f = function () { return new \FooCommand(); },
+        )));
 
         $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');

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

@@ -0,0 +1,60 @@
+<?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\FactoryCommandLoader;
+
+class FactoryCommandLoaderTest extends TestCase
+{
+    public function testHas()
+    {
+        $loader = new FactoryCommandLoader(array(
+            'foo' => function () { return new Command('foo'); },
+            'bar' => function () { return new Command('bar'); },
+        ));
+
+        $this->assertTrue($loader->has('foo'));
+        $this->assertTrue($loader->has('bar'));
+        $this->assertFalse($loader->has('baz'));
+    }
+
+    public function testGet()
+    {
+        $loader = new FactoryCommandLoader(array(
+            'foo' => function () { return new Command('foo'); },
+            'bar' => function () { return new Command('bar'); },
+        ));
+
+        $this->assertInstanceOf(Command::class, $loader->get('foo'));
+        $this->assertInstanceOf(Command::class, $loader->get('bar'));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Console\Exception\CommandNotFoundException
+     */
+    public function testGetUnknownCommandThrows()
+    {
+        (new FactoryCommandLoader(array()))->get('unknown');
+    }
+
+    public function testGetCommandNames()
+    {
+        $loader = new FactoryCommandLoader(array(
+            'foo' => function () { return new Command('foo'); },
+            'bar' => function () { return new Command('bar'); },
+        ));
+
+        $this->assertSame(array('foo', 'bar'), $loader->getNames());
+    }
+}