Define stub for cache object shape (#724)

* Define stub for cache object shape

Fixes #270

* Keep PHP 7.4 support

Author: mglaman

stubs/Drupal/Core/Cache/CacheBackendInterface.stub

@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\Core\Cache;
+
+/**
+ * @phpstan-type CacheObject object{data: mixed, created: int, tags: string[], valid: bool, expire: int, checksum: string, serialized: int}
+ */
+interface CacheBackendInterface {
+
+    /**
+     * @return CacheObject|false
+     */
+    public function get(string $cid, bool $allow_invalid = FALSE);
+
+    /**
+     * @param string[] $cids
+     * @return CacheObject[]
+     */
+    public function getMultiple(array &$cids, bool $allow_invalid = FALSE): array;
+}

tests/src/Type/CacheBackendInterfaceStubTest.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Type;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class CacheBackendInterfaceStubTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/cache-backend-interface-stub.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}

tests/src/Type/data/cache-backend-interface-stub.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace CacheBackendInterfaceStub;
+
+use Drupal\Core\Cache\DatabaseBackend;
+use Drupal\Core\Cache\MemoryBackend;
+use function PHPStan\Testing\assertType;
+
+$cids = ['foo'];
+
+assert($dbBackend instanceof DatabaseBackend);
+assertType('object{data: mixed, created: int, tags: array<string>, valid: bool, expire: int, checksum: string, serialized: int}|false', $dbBackend->get('foo'));
+assertType('array<object{data: mixed, created: int, tags: array<string>, valid: bool, expire: int, checksum: string, serialized: int}>', $dbBackend->getMultiple($cids));
+
+assert($memoryBackend instanceof MemoryBackend);
+assertType('object{data: mixed, created: int, tags: array<string>, valid: bool, expire: int, checksum: string, serialized: int}|false', $memoryBackend->get('foo'));
+assertType('array<object{data: mixed, created: int, tags: array<string>, valid: bool, expire: int, checksum: string, serialized: int}>', $memoryBackend->getMultiple($cids));