From a3b1e3b4eecf455bbb3438b7d3f31c0175c2c7aa Mon Sep 17 00:00:00 2001
From: sam marshall <s.marshall@open.ac.uk>
Date: Tue, 3 Jan 2023 17:59:53 +0000
Subject: [PATCH] MDL-76784 core_cache: versioned cache (modinfo) can fail in
 install

When cache is disabled but temporary in-memory caches are allowed,
these were direct instances of cachestore_static with no loader, which
meant that the get_versioned and set_versioned functions did not work.
---
 cache/disabledlib.php                       |  9 ++++--
 cache/tests/allow_temporary_caches_test.php | 34 +++++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/cache/disabledlib.php b/cache/disabledlib.php
index 380a474804397..510d77a4fc468 100644
--- a/cache/disabledlib.php
+++ b/cache/disabledlib.php
@@ -294,8 +294,13 @@ public function create_cache_from_definition($component, $area, array $identifie
                 $definition = $this->create_definition($component, $area);
                 // The cachestore_static class returns true to all three 'SUPPORTS_' checks so it
                 // can be used with all definitions.
-                $cache = new cachestore_static('TEMP:' . $component . '/' . $area);
-                $cache->initialise($definition);
+                $store = new cachestore_static('TEMP:' . $component . '/' . $area);
+                $store->initialise($definition);
+                // We need to use a cache loader wrapper rather than directly returning the store,
+                // or it wouldn't have support for versioning. The cache_application class is used
+                // (rather than cache_request which might make more sense logically) because it
+                // includes support for locking, which might be necessary for some caches.
+                $cache = new cache_application($definition, $store);
                 self::$tempcaches[$key] = $cache;
             }
             return $cache;
diff --git a/cache/tests/allow_temporary_caches_test.php b/cache/tests/allow_temporary_caches_test.php
index 4fd950b953850..cd1879830f61d 100644
--- a/cache/tests/allow_temporary_caches_test.php
+++ b/cache/tests/allow_temporary_caches_test.php
@@ -62,4 +62,38 @@ protected function inner_is_allowed(): void {
         $gecko = new allow_temporary_caches();
         $this->assertTrue(allow_temporary_caches::is_allowed());
     }
+
+    /**
+     * Tests that the temporary caches actually work, including normal and versioned get and set.
+     */
+    public function test_temporary_cache(): void {
+        $this->resetAfterTest();
+
+        // Disable the cache.
+        \cache_phpunit_factory::phpunit_disable();
+        try {
+            // Try using the cache now - it returns false/null for everything.
+            $cache = \cache::make('core', 'coursemodinfo');
+            $cache->set('frog', 'ribbit');
+            $this->assertFalse($cache->get('frog'));
+            $cache->set_versioned('toad', 2, 'croak');
+            $this->assertFalse($cache->get_versioned('toad', 2));
+
+            // But when we allow temporary caches, it should work as normal.
+            $allow = new allow_temporary_caches();
+            $cache = \cache::make('core', 'coursemodinfo');
+            $cache->set('frog', 'ribbit');
+            $this->assertEquals('ribbit', $cache->get('frog'));
+            $cache->set_versioned('toad', 2, 'croak');
+            $this->assertEquals('croak', $cache->get_versioned('toad', 2));
+
+            // Let's actually use modinfo, to check it works with locking too.
+            $course = $this->getDataGenerator()->create_course();
+            get_fast_modinfo($course);
+        } finally {
+            // You have to do this after phpunit_disable or it breaks later tests.
+            \cache_factory::reset();
+            \cache_factory::instance(true);
+        }
+    }
 }