A configuration value is resolved once per request

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- The configuration values a request read are answered from a request memo on the second read, under the `config_memo` switch: no scope resolution and no type lookup per read.
+
+## Unreleased
+
 - The stock id of the current website as a cache entry in the local files, from the new FastBootInventory module: no sales channel select per request. A change of a stock's sales channels cleans it.
 
 ## 0.2.0-rc8

dev/README.md

@@ -30,6 +30,7 @@ Production installs use the default-enabled optimizations. These switches suppor
 | `tax_rates` | Tax rates and applied rates per rate request from the cache, for requests that are not customer-specific. | Yes |
 | `customer_groups` | Customer groups by id from the cache, with their excluded websites. | Yes |
 | `currency_rates` | Currency rates from the cache; a rate import cleans them. | Yes |
+| `config_memo` | The configuration values a request read, by scope, scope code and path; a clean, a mutable set and a store switch empty it. | No |
 | `stock_id` | The stock id of the current website from the cache; a change of a stock's sales channels cleans it. | Yes |
 
 These switches do not enable PHP class preload; that requires `opcache.preload` at FPM startup.

src/FastBoot/Plugin/Config/ForgetValueMemo.php

@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+
+namespace GraphCommerce\FastBoot\Plugin\Config;
+
+/**
+ * Empties the value memo after a mutable configuration set and after a switch of the
+ * current store, the two events that change what a read with the current scope answers.
+ */
+class ForgetValueMemo
+{
+    public function __construct(
+        private readonly ValueMemo $memo,
+    ) {
+    }
+
+    /**
+     * @param object $subject
+     * @param mixed $result
+     * @return mixed
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function afterSetValue(object $subject, $result)
+    {
+        $this->memo->forget();
+
+        return $result;
+    }
+
+    /**
+     * @param object $subject
+     * @param mixed $result
+     * @return mixed
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function afterSetCurrentStore(object $subject, $result)
+    {
+        $this->memo->forget();
+
+        return $result;
+    }
+}

src/FastBoot/Plugin/Config/ValueMemo.php

@@ -0,0 +1,66 @@
+<?php
+declare(strict_types=1);
+
+namespace GraphCommerce\FastBoot\Plugin\Config;
+
+use GraphCommerce\FastBootCache\Model\Feature;
+use Magento\Framework\App\Config;
+use Magento\Framework\ObjectManager\ResetAfterRequestInterface;
+
+/**
+ * The values a request read from the system configuration, by scope, scope code and path,
+ * so a second read of the same value skips the scope resolution and the type lookup. A
+ * clean of the configuration, a mutable set and a switch of the current store empty it.
+ */
+class ValueMemo implements ResetAfterRequestInterface
+{
+    private const SWITCH = 'config_memo';
+
+    /** @var array<string, mixed> */
+    private array $values = [];
+
+    public function __construct(
+        private readonly Feature $feature,
+    ) {
+    }
+
+    /**
+     * @param mixed $path
+     * @param mixed $scope
+     * @param mixed $scopeCode
+     * @return mixed
+     */
+    public function aroundGetValue(Config $subject, callable $proceed, $path = null, $scope = 'default', $scopeCode = null)
+    {
+        if (($scopeCode !== null && !is_scalar($scopeCode)) || !$this->feature->on(self::SWITCH)) {
+            return $proceed($path, $scope, $scopeCode);
+        }
+        $key = $scope . "\0" . ($scopeCode ?? '') . "\0" . $path;
+        if (!array_key_exists($key, $this->values)) {
+            $this->values[$key] = $proceed($path, $scope, $scopeCode);
+        }
+
+        return $this->values[$key];
+    }
+
+    /**
+     * @param mixed $result
+     * @return mixed
+     */
+    public function afterClean(Config $subject, $result)
+    {
+        $this->values = [];
+
+        return $result;
+    }
+
+    public function forget(): void
+    {
+        $this->values = [];
+    }
+
+    public function _resetState(): void
+    {
+        $this->values = [];
+    }
+}

src/FastBoot/Test/Unit/Plugin/Config/ValueMemoTest.php

@@ -0,0 +1,82 @@
+<?php
+declare(strict_types=1);
+
+namespace GraphCommerce\FastBoot\Test\Unit\Plugin\Config;
+
+use GraphCommerce\FastBoot\Plugin\Config\ForgetValueMemo;
+use GraphCommerce\FastBoot\Plugin\Config\ValueMemo;
+use GraphCommerce\FastBootCache\Model\Feature;
+use Magento\Framework\App\Config;
+use Magento\Framework\App\Config\MutableScopeConfigInterface;
+use PHPUnit\Framework\TestCase;
+
+class ValueMemoTest extends TestCase
+{
+    private int $reads = 0;
+
+    private function memo(): ValueMemo
+    {
+        $this->reads = 0;
+        $feature = $this->createStub(Feature::class);
+        $feature->method('on')->willReturn(true);
+
+        return new ValueMemo($feature);
+    }
+
+    private function read(ValueMemo $memo, string $path, string $scope = 'default', mixed $code = null): mixed
+    {
+        return $memo->aroundGetValue($this->createStub(Config::class), function ($path) {
+            $this->reads++;
+
+            return $path === 'a/null' ? null : strtoupper($path);
+        }, $path, $scope, $code);
+    }
+
+    public function testASecondReadOfTheSameValueSkipsTheConfiguration(): void
+    {
+        $memo = $this->memo();
+
+        $this->assertSame('A/B', $this->read($memo, 'a/b', 'store'));
+        $this->assertSame('A/B', $this->read($memo, 'a/b', 'store'));
+        $this->assertNull($this->read($memo, 'a/null'));
+        $this->assertNull($this->read($memo, 'a/null'));
+        $this->assertSame(2, $this->reads);
+    }
+
+    public function testTheScopeAndTheCodeAreInTheKey(): void
+    {
+        $memo = $this->memo();
+
+        $this->read($memo, 'a/b', 'store');
+        $this->read($memo, 'a/b', 'store', 'second');
+        $this->read($memo, 'a/b', 'website');
+
+        $this->assertSame(3, $this->reads);
+    }
+
+    public function testACleanAMutableSetAndAStoreSwitchEmptyTheMemo(): void
+    {
+        $memo = $this->memo();
+        $forget = new ForgetValueMemo($memo);
+
+        $this->read($memo, 'a/b');
+        $memo->afterClean($this->createStub(Config::class), null);
+        $this->read($memo, 'a/b');
+        $forget->afterSetValue($this->createStub(MutableScopeConfigInterface::class), null);
+        $this->read($memo, 'a/b');
+        $forget->afterSetCurrentStore(new \stdClass(), null);
+        $this->read($memo, 'a/b');
+
+        $this->assertSame(4, $this->reads);
+    }
+
+    public function testAScopeObjectAsCodeIsNotMemoised(): void
+    {
+        $memo = $this->memo();
+
+        $this->read($memo, 'a/b', 'store', new \stdClass());
+        $this->read($memo, 'a/b', 'store', new \stdClass());
+
+        $this->assertSame(2, $this->reads);
+    }
+}

src/FastBoot/etc/di.xml

@@ -22,6 +22,17 @@
     <preference for="Magento\Framework\Config\View" type="GraphCommerce\FastBoot\Model\Config\OpcacheView"/>
     <preference for="Magento\Framework\Config\ViewFactory" type="GraphCommerce\FastBoot\Model\Config\OpcacheViewFactory"/>
 
+    <!-- The values a request read, by scope, scope code and path: the second read skips the scope resolution and the type lookup. -->
+    <type name="Magento\Framework\App\Config">
+        <plugin name="graphcommerce_fastboot_config_value_memo" type="GraphCommerce\FastBoot\Plugin\Config\ValueMemo"/>
+    </type>
+    <type name="Magento\Framework\App\Config\MutableScopeConfigInterface">
+        <plugin name="graphcommerce_fastboot_forget_config_value_memo" type="GraphCommerce\FastBoot\Plugin\Config\ForgetValueMemo"/>
+    </type>
+    <type name="Magento\Store\Model\StoreManagerInterface">
+        <plugin name="graphcommerce_fastboot_forget_config_value_memo" type="GraphCommerce\FastBoot\Plugin\Config\ForgetValueMemo"/>
+    </type>
+
     <!-- The system configuration of every scope as one opcache PHP array: no decrypt and no unserialise per request. -->
     <type name="Magento\Config\App\Config\Type\System">
         <plugin name="graphcommerce_fastboot_system_from_file" type="GraphCommerce\FastBoot\Plugin\Config\SystemFromFile"/>