[TASK] Introduce Map data-structure

Unfortunately PHP emphasizes "weak" over "map" in their new PHP 8
data-structure `\WeakMap`. As a result it cannot be passed to other
functions that would enrich an existing `\WeakMap` - since objects
created in that function scope would not exist outside and thus
directly trigger garbage collection of `\WeakMap`.

`\SplObjectStorage` has a strange behavior when using an iteration
like `foreach ($map as $key => $value)` - the `$value` is actually
the `$key` for BC reasons.

As a substitute, `\TYPO3\CMS\Core\Type\Map` is introduced which has a
similar behavior and got an additional `Map::fromEntries()` factory.
It acts as a wrapper of `\SplObjectStorage` with reduced features.

Example:

$map = new \TYPO3\CMS\Core\Type\Map();
$key = new \stdClass();
$value = new \stdClass();
$map[$key] = $value;

foreach ($map as $key => $value) { ... }

Resolves: #100168
Releases: main
Change-Id: I5c26dc4aa9b4679112a27bd4cbebcfbe0899b094
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78127


Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>

typo3/sysext/core/Classes/Type/Map.php

+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Type;
+
+/**
+ * Map implementation that supports objects as keys.
+ *
+ * PHP's \WeakMap is not an option in case object keys are created and assigned
+ * in an encapsulated scope (like passing a map to a function to enrich it). In
+ * case the original object is not referenced anymore, it also will vanish from
+ * a \WeakMap, when used as key (see https://www.php.net/manual/class.weakmap.php).
+ *
+ * PHP's \SplObjectStorage has a strange behavior when using an iteration like
+ * `foreach ($map as $key => $value)` - the `$value` is actually the `$key` for
+ * BC reasons (see https://bugs.php.net/bug.php?id=49967).
+ *
+ * This individual implementation works around the "weak" behavior of \WeakMap
+ * and the iteration issue with `foreach` of `\SplObjectStorage` by acting as
+ * a wrapper for `\SplObjectStorage` with reduced features.
+ *
+ * Example:
+ * ```
+ * $map = new \TYPO3\CMS\Core\Type\Map();
+ * $key = new \stdClass();
+ * $value = new \stdClass();
+ * $map[$key] = $value;
+ *
+ * foreach ($map as $key => $value) { ... }
+ * ```
+ */
+final class Map implements \ArrayAccess, \Countable, \Iterator
+{
+    private \SplObjectStorage $storage;
+
+    /**
+     * @template E array{0:mixed, 1:mixed}
+     * @param list<E> $entries
+     */
+    public static function fromEntries(array ...$entries): self
+    {
+        $map = new self();
+        foreach ($entries as $entry) {
+            $map[$entry[0]] = $entry[1];
+        }
+        return $map;
+    }
+
+    public function __construct()
+    {
+        $this->storage = new \SplObjectStorage();
+    }
+
+    public function key(): mixed
+    {
+        return $this->storage->current();
+    }
+
+    public function current(): mixed
+    {
+        return $this->storage->getInfo();
+    }
+
+    public function next(): void
+    {
+        $this->storage->next();
+    }
+
+    public function rewind(): void
+    {
+        $this->storage->rewind();
+    }
+
+    public function valid(): bool
+    {
+        return $this->storage->valid();
+    }
+
+    public function offsetExists(mixed $offset): bool
+    {
+        return $this->storage->offsetExists($offset);
+    }
+
+    public function offsetGet(mixed $offset): mixed
+    {
+        return $this->storage->offsetGet($offset);
+    }
+
+    public function offsetSet(mixed $offset, mixed $value): void
+    {
+        $this->storage->offsetSet($offset, $value);
+    }
+
+    public function offsetUnset(mixed $offset): void
+    {
+        $this->storage->offsetUnset($offset);
+    }
+
+    public function count(): int
+    {
+        return count($this->storage);
+    }
+}

typo3/sysext/core/Tests/Unit/Type/MapTest.php

+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Tests\Unit\Type;
+
+use TYPO3\CMS\Core\Type\Map;
+use TYPO3\TestingFramework\Core\Unit\UnitTestCase;
+
+class MapTest extends UnitTestCase
+{
+    /**
+     * @test
+     */
+    public function mapIsArrayAccessible(): void
+    {
+        $aKey = new \stdClass();
+        $aValue = new \stdClass();
+        $bKey = new \stdClass();
+        $bValue = new \stdClass();
+
+        $map = new Map();
+        $map[$aKey] = $aValue;
+        $map[$bKey] = $bValue;
+
+        self::assertInstanceOf(Map::class, $map);
+        self::assertCount(2, $map);
+        self::assertSame($aValue, $map[$aKey]);
+        self::assertSame($bValue, $map[$bKey]);
+    }
+
+    /**
+     * @test
+     */
+    public function mapKeyCanBeUnset(): void
+    {
+        $aKey = new \stdClass();
+        $aValue = new \stdClass();
+        $bKey = new \stdClass();
+        $bValue = new \stdClass();
+
+        $map = new Map();
+        $map[$aKey] = $aValue;
+        $map[$bKey] = $bValue;
+
+        unset($map[$bKey]);
+
+        self::assertCount(1, $map);
+        self::assertFalse(isset($map[$bKey]));
+    }
+
+    /**
+     * @test
+     */
+    public function mapCanBeIterated(): void
+    {
+        $aKey = new \stdClass();
+        $aValue = new \stdClass();
+        $bKey = new \stdClass();
+        $bValue = new \stdClass();
+
+        $map = new Map();
+        $map[$aKey] = $aValue;
+        $map[$bKey] = $bValue;
+
+        $entries = [];
+        foreach ($map as $key => $value) {
+            $entries[] = [$key, $value];
+        }
+
+        $expectation = [
+            [$aKey, $aValue],
+            [$bKey, $bValue],
+        ];
+        self::assertSame($expectation, $entries);
+    }
+
+    /**
+     * @test
+     */
+    public function mapIsCreatedFromEntries(): void
+    {
+        $aKey = new \stdClass();
+        $aValue = new \stdClass();
+        $bKey = new \stdClass();
+        $bValue = new \stdClass();
+
+        $map = Map::fromEntries(
+            [$aKey, $aValue],
+            [$bKey, $bValue],
+        );
+
+        self::assertCount(2, $map);
+        self::assertSame($aValue, $map[$aKey]);
+        self::assertSame($bValue, $map[$bKey]);
+    }
+}