Fix multisite extension discovery by scanning all sites/*/ directories

src/Drupal/ExtensionDiscovery.php

@@ -6,6 +6,7 @@
 use mglaman\PHPStanDrupal\Drupal\Extension;
 use RecursiveDirectoryIterator;
 use RecursiveIteratorIterator;
+use Symfony\Component\Finder\Finder;
 use function array_filter;
 use function array_flip;
 use function array_multisort;
@@ -72,11 +73,11 @@ class ExtensionDiscovery
     protected $root;
 
     /**
-     * The site path.
+     * The site paths.
      *
-     * @var string
+     * @var string[]
      */
-    protected $sitePath;
+    protected $sitePaths;
 
     /**
      * Constructs a new ExtensionDiscovery object.
@@ -90,7 +91,27 @@ public function __construct($root)
         $this->profileDirectories = [
             $root . '/core/profiles/standard'
         ];
-        $this->sitePath = 'sites/default';
+        $this->sitePaths = $this->discoverSitePaths();
+    }
+
+    /**
+     * Discovers all site-specific directories under sites/.
+     *
+     * @return string[]
+     *   An array of site paths relative to the root (e.g. 'sites/default').
+     */
+    private function discoverSitePaths(): array
+    {
+        $sitesDir = $this->root . '/sites';
+        if (!is_dir($sitesDir)) {
+            return [];
+        }
+        $finder = Finder::create()->directories()->in($sitesDir)->depth(0)->exclude(['all', 'default', 'simpletest']);
+        $paths = [];
+        foreach ($finder as $dir) {
+            $paths[] = 'sites/' . $dir->getFilename();
+        }
+        return $paths;
     }
 
     /**
@@ -152,7 +173,12 @@ public function scan($type)
         // type specific directory names only.
         $searchdirs[self::ORIGIN_ROOT] = '';
 
-        $searchdirs[self::ORIGIN_SITE] = $this->sitePath;
+        // Search the default site-specific directory, plus any additional site
+        // directories discovered for multisite setups.
+        $searchdirs[self::ORIGIN_SITE] = 'sites/default';
+        foreach ($this->sitePaths as $sitePath) {
+            $searchdirs[] = $sitePath;
+        }
 
         $files = [];
         foreach ($searchdirs as $dir) {

tests/fixtures/drupal/sites/acme/modules/acme_module/acme_module.inc

@@ -0,0 +1,10 @@
+<?php
+
+/**
+ * @file
+ * Include file for the site specific module fixture.
+ */
+
+function site_specific_module_helper(): string {
+  return 'helper';
+}

tests/fixtures/drupal/sites/acme/modules/acme_module/acme_module.info.yml

@@ -0,0 +1,3 @@
+name: Acme site specific module
+type: module
+core: 8.x

tests/fixtures/drupal/sites/acme/modules/acme_module/acme_module.module

@@ -0,0 +1,6 @@
+<?php
+
+/**
+ * @file
+ * Module file for the site specific module fixture.
+ */

tests/src/Rules/LoadIncludesRuleTest.php

@@ -66,6 +66,11 @@ public static function cases(): \Generator
                 ],
             ]
         ];
+
+        yield 'multisite module in sites/acme/' => [
+            [__DIR__.'/data/multisite-load-include.php'],
+            []
+        ];
     }
 
 }

tests/src/Rules/data/multisite-load-include.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace MultisiteLoadInclude;
+
+/**
+ * Tests that loadInclude works for modules in non-default site directories.
+ *
+ * This demonstrates a bug where ExtensionDiscovery only scanned sites/default,
+ * causing modules under other site directories (e.g. sites/acme/)
+ * to not be found.
+ */
+function test_multisite_load_include(): void {
+  \Drupal::moduleHandler()->loadInclude('acme_module', 'inc');
+}