Fix issues mentionned by @mahagr's review.

Indeed, I was not using composer to autoload everything which is needeed.

Also:
  * Reverse changes regarding the files locations.

composer.json

@@ -1,16 +1,25 @@
 {
-    "name": "amaurycarrade/grav-plugin-static-social-embeds",
-    "description": "Embeds social status (like tweets, instagram posts, toots, etc.) in articles without using their embed iframe, but rather statically without any dependency to the service.",
-    "type": "project",
-    "require": {
-        "jedkirby/tweet-entity-linker": "^1.2"
+  "name": "amaurycarrade/grav-plugin-static-social-embeds",
+  "description": "Embeds social status (like tweets, instagram posts, toots, etc.) in articles without using their embed iframe, but rather statically without any dependency to the service.",
+  "type": "project",
+  "require": {
+    "jedkirby/tweet-entity-linker": "^1.2"
+  },
+  "license": "MIT",
+  "authors": [
+    {
+      "name": "Amaury Carrade",
+      "email": "[email protected]"
+    }
+  ],
+  "minimum-stability": "stable",
+  "autoload": {
+    "psr-4": {
+      "Grav\\Plugin\\Shortcodes\\": "shortcodes"
     },
-    "license": "MIT",
-    "authors": [
-        {
-            "name": "Amaury Carrade",
-            "email": "[email protected]"
-        }
-    ],
-    "minimum-stability": "stable"
-}
+    "classmap": [
+      "static-social-embeds.php",
+      "classes/SSEShortcode.php"
+    ]
+  }
+}

static-social-embeds.php

@@ -52,8 +52,6 @@ public function onPluginsInitialized()
             return;
         }
 
-        require_once __DIR__ . '/classes/plugin/SSEShortcode.php';
-
         // Enable the main event we are interested in
         $this->enable([
             'onShortcodeHandlers' => ['onShortcodeHandlers', 0],
@@ -96,6 +94,6 @@ public function onAssetsInitialized()
      */
     public function onShortcodeHandlers()
     {
-        $this->grav['shortcode']->registerAllShortcodes(__DIR__ . '/classes/shortcodes');
+        $this->grav['shortcode']->registerAllShortcodes(__DIR__ . '/shortcodes');
     }
 }

vendor/composer/ClassLoader.php

@@ -279,7 +279,7 @@ public function isClassMapAuthoritative()
      */
     public function setApcuPrefix($apcuPrefix)
     {
-        $this->apcuPrefix = function_exists('apcu_fetch') && ini_get('apc.enabled') ? $apcuPrefix : null;
+        $this->apcuPrefix = function_exists('apcu_fetch') && filter_var(ini_get('apc.enabled'), FILTER_VALIDATE_BOOLEAN) ? $apcuPrefix : null;
     }
 
     /**
@@ -377,11 +377,11 @@ private function findFileWithExtension($class, $ext)
             $subPath = $class;
             while (false !== $lastPos = strrpos($subPath, '\\')) {
                 $subPath = substr($subPath, 0, $lastPos);
-                $search = $subPath.'\\';
+                $search = $subPath . '\\';
                 if (isset($this->prefixDirsPsr4[$search])) {
+                    $pathEnd = DIRECTORY_SEPARATOR . substr($logicalPathPsr4, $lastPos + 1);
                     foreach ($this->prefixDirsPsr4[$search] as $dir) {
-                        $length = $this->prefixLengthsPsr4[$first][$search];
-                        if (file_exists($file = $dir . DIRECTORY_SEPARATOR . substr($logicalPathPsr4, $length))) {
+                        if (file_exists($file = $dir . $pathEnd)) {
                             return $file;
                         }
                     }

vendor/composer/autoload_classmap.php

@@ -6,4 +6,6 @@
 $baseDir = dirname($vendorDir);
 
 return array(
+    'Grav\\Plugin\\Shortcodes\\SSEShortcode' => $baseDir . '/classes/SSEShortcode.php',
+    'Grav\\Plugin\\StaticSocialEmbedsPlugin' => $baseDir . '/static-social-embeds.php',
 );

vendor/composer/autoload_psr4.php

@@ -7,4 +7,5 @@
 
 return array(
     'Jedkirby\\TweetEntityLinker\\' => array($vendorDir . '/jedkirby/tweet-entity-linker/src'),
+    'Grav\\Plugin\\Shortcodes\\' => array($baseDir . '/shortcodes'),
 );

vendor/composer/autoload_static.php

@@ -11,20 +11,34 @@ class ComposerStaticInit1c781dd30cc1c5fc04980a1fc07fda14
         array (
             'Jedkirby\\TweetEntityLinker\\' => 27,
         ),
+        'G' => 
+        array (
+            'Grav\\Plugin\\Shortcodes\\' => 23,
+        ),
     );
 
     public static $prefixDirsPsr4 = array (
         'Jedkirby\\TweetEntityLinker\\' => 
         array (
             0 => __DIR__ . '/..' . '/jedkirby/tweet-entity-linker/src',
         ),
+        'Grav\\Plugin\\Shortcodes\\' => 
+        array (
+            0 => __DIR__ . '/../..' . '/shortcodes',
+        ),
+    );
+
+    public static $classMap = array (
+        'Grav\\Plugin\\Shortcodes\\SSEShortcode' => __DIR__ . '/../..' . '/classes/SSEShortcode.php',
+        'Grav\\Plugin\\StaticSocialEmbedsPlugin' => __DIR__ . '/../..' . '/static-social-embeds.php',
     );
 
     public static function getInitializer(ClassLoader $loader)
     {
         return \Closure::bind(function () use ($loader) {
             $loader->prefixLengthsPsr4 = ComposerStaticInit1c781dd30cc1c5fc04980a1fc07fda14::$prefixLengthsPsr4;
             $loader->prefixDirsPsr4 = ComposerStaticInit1c781dd30cc1c5fc04980a1fc07fda14::$prefixDirsPsr4;
+            $loader->classMap = ComposerStaticInit1c781dd30cc1c5fc04980a1fc07fda14::$classMap;
 
         }, null, ClassLoader::class);
     }