[ObjectOriented] Introduce ObjectOriented component

src/Psl/Internal/Loader.php

@@ -456,6 +456,11 @@ final class Loader
         'Psl\Encoding\Base64\decode',
         'Psl\Encoding\Hex\encode',
         'Psl\Encoding\Hex\decode',
+        'Psl\ObjectOriented\class_alias',
+        'Psl\ObjectOriented\class_exists',
+        'Psl\ObjectOriented\interface_exists',
+        'Psl\ObjectOriented\trait_exists',
+        'Psl\ObjectOriented\get_class',
     ];
 
     public const INTERFACES = [

src/Psl/ObjectOriented/class_alias.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\ObjectOriented;
+
+use function class_alias as php_class_alias;
+use function function_exists as php_function_exists;
+
+/**
+ * Creates an alias for a class.
+ *
+ * Example:
+ *
+ *      $class_name = Collection\Vector::class;
+ *      $alias = 'AwesomeVector';
+ *
+ *      ObjectOriented\class_alias($class_name, $alias);
+ *      => Bool(true)
+ *
+ *      $vector = new $alias(['a', 'b']);
+ *
+ *      Type\object($class_name)->matches($vector);
+ *      => Bool(true)
+ *
+ * @template T
+ *
+ * @param class-string<T> $class_name
+ *
+ * @psalm-assert-if-true class-string<T> $alias
+ *
+ * @return bool Returns false if unable to create an alias.
+ */
+function class_alias(string $class_name, string $alias): bool
+{
+    // This is a weird scenario.
+    // assuming $alias is `Psl\Str\contains`
+    // attempting to call `class_exists` will result in the autoloader being triggered.
+    // trying to find the class `Psl\Str\contains`.
+    // this results composer autoloader including `src/Psl/Str/contains.php` again,
+    // which contains the function definition, leading to a fatal error due to
+    // redeclaration of the function.
+    //
+    // so we have to ensure we don't call `*_exists` function in this case.
+    if (!php_function_exists($alias)) {
+        if (class_exists($alias)) {
+            return false;
+        }
+
+        if (interface_exists($alias)) {
+            return false;
+        }
+
+        if (trait_exists($alias)) {
+            return false;
+        }
+    }
+
+    return php_class_alias($class_name, $alias);
+}

src/Psl/ObjectOriented/class_exists.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\ObjectOriented;
+
+use function class_exists as php_class_exists;
+
+/**
+ * Checks if the class has been defined.
+ *
+ * Example:
+ *
+ *      ObjectOriented\class_exists('Psl\Collection\Vector');
+ *      => Bool(true)
+ *
+ *      ObjectOriented\class_exists('Psl\Collection\Foo');
+ *      => Bool(false)
+ *
+ * @psalm-assert-if-true class-string $class_name
+ */
+function class_exists(string $class_name): bool
+{
+    return php_class_exists($class_name);
+}

src/Psl/ObjectOriented/get_class.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\ObjectOriented;
+
+use function get_class as php_get_class;
+
+/**
+ * Returns the name of the class of an object.
+ *
+ * Example:
+ *
+ *      ObjectOriented\get_class($vector);
+ *      => Str('Psl\Collection\Vector')
+ *
+ * @template T of object
+ *
+ * @param T $object
+ *
+ * @return class-string<T>
+ *
+ * @psalm-pure
+ */
+function get_class(object $object): string
+{
+    return php_get_class($object);
+}

src/Psl/ObjectOriented/interface_exists.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\ObjectOriented;
+
+use function interface_exists as php_interface_exists;
+
+/**
+ * Checks if the interface has been defined.
+ *
+ * Example:
+ *
+ *      ObjectOriented\interface_exists('Psl\Collection\VectorInterface');
+ *      => Bool(true)
+ *
+ *      ObjectOriented\interface_exists('Psl\Collection\FooInterface');
+ *      => Bool(false)
+ *
+ */
+function interface_exists(string $interface_name): bool
+{
+    return php_interface_exists($interface_name);
+}

src/Psl/ObjectOriented/trait_exists.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\ObjectOriented;
+
+use function trait_exists as php_trait_exists;
+
+/**
+ * Checks if the trait has been defined.
+ *
+ * Example:
+ *
+ *      ObjectOriented\class_exists('Psl\Collection\Vector');
+ *      => Bool(true)
+ *
+ *      ObjectOriented\class_exists('Psl\Collection\Foo');
+ *      => Bool(false)
+ *
+ *
+ * @psalm-assert-if-true class-string $class_name
+ */
+function trait_exists(string $trait_name): bool
+{
+    // PHPs trait_exists returns null in case of an error.
+    return php_trait_exists($trait_name) ?? false;
+}

tests/Psl/ObjectOriented/ClassAliasTest.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\Iter;
+use Psl\ObjectOriented;
+use Psl\Type;
+
+final class ClassAliasTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testClassAlias(bool $expected, object $object, string $alias): void
+    {
+        $class_name = ObjectOriented\get_class($object);
+
+        static::assertSame($expected, ObjectOriented\class_alias($class_name, $alias));
+
+        if ($expected) {
+            // Assert alias class exists.
+            static::assertTrue(ObjectOriented\class_exists($alias));
+
+            // Assert an instanceof $class_name is also an instanceof $alias
+            static::assertTrue(Type\object($alias)->matches($object));
+        }
+    }
+
+    public function provideData(): iterable
+    {
+        yield [
+            true,
+            new Collection\MutableVector([]),
+            'Psl\Tests\ObjectOriented\Collection\MutableVectorAlias'
+        ];
+
+        yield [
+            true,
+            Iter\Iterator::create([]),
+            'Psl\Tests\ObjectOriented\Iter\Iterator'
+        ];
+
+        yield [
+            false,
+            Iter\Iterator::create([]),
+            Collection\MutableVector::class
+        ];
+
+        yield [
+            false,
+            Iter\Iterator::create([]),
+            Collection\MutableVectorInterface::class
+        ];
+
+        yield [
+            false,
+            Iter\Iterator::create([]),
+            Fixture\EmptyTrait::class
+        ];
+
+        yield [
+            true,
+            Iter\Iterator::create([]),
+            'Psl\Str\contains'
+        ];
+    }
+}

tests/Psl/ObjectOriented/ClassExistsTest.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\ObjectOriented;
+
+final class ClassExistsTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testClassExists(bool $expected, string $class_name): void
+    {
+        static::assertSame($expected, ObjectOriented\class_exists($class_name));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [true, Collection\MutableVector::class];
+        yield [false, 'Collection\MutableVector'];
+    }
+}

tests/Psl/ObjectOriented/Fixture/EmptyTrait.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented\Fixture;
+
+trait EmptyTrait
+{
+}

tests/Psl/ObjectOriented/GetClassTest.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\Iter;
+use Psl\ObjectOriented;
+
+final class GetClassTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testGetClass(string $expected, object $object): void
+    {
+        static::assertSame($expected, ObjectOriented\get_class($object));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [
+            Collection\MutableVector::class,
+            new Collection\MutableVector([])
+        ];
+
+        yield [
+            Iter\Iterator::class,
+            Iter\Iterator::create([]),
+        ];
+    }
+}

tests/Psl/ObjectOriented/InterfaceExistsTest.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\ObjectOriented;
+
+final class InterfaceExistsTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testInterfaceExists(bool $expected, string $interface_name): void
+    {
+        static::assertSame($expected, ObjectOriented\interface_exists($interface_name));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [true, Collection\MutableVectorInterface::class];
+        yield [false, Collection\MutableVector::class];
+        yield [false, 'Foo\Interface'];
+    }
+}

tests/Psl/ObjectOriented/TraitExistsTest.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\ObjectOriented;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\ObjectOriented;
+
+final class TraitExistsTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testTraitExists(bool $expected, string $trait_name): void
+    {
+        static::assertSame($expected, ObjectOriented\trait_exists($trait_name));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [true, Fixture\EmptyTrait::class];
+        yield [false, Collection\MutableVectorInterface::class];
+        yield [false, Collection\MutableVector::class];
+        yield [false, 'Foo\Interface'];
+    }
+}