New core-extensions to allow Docker volumes for third-party extensions (#2837)

* New core-extensions to allow Docker volumes for third-party extensions

#Fix https://github.com/FreshRSS/FreshRSS/issues/2650
Split our extensions directory into two:
1) Core extensions shipped with FreshRSS in ./lib/core-extensions/
2) Third-party extensions modified by end-users in ./extensions/ which
can easily be mounted as a Docker volume

* Example of Docker Compose with extensions

* Back-compatibility + fix array merge bug

5 files changed, 39 insertions, 8 deletions

diff --git a/lib/Minz/ExtensionManager.php b/lib/Minz/ExtensionManager.php
index e6b8dafb0..b2814e4a3 100644
--- a/lib/Minz/ExtensionManager.php
+++ b/lib/Minz/ExtensionManager.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * An extension manager to load extensions present in EXTENSIONS_PATH.
+ * An extension manager to load extensions present in CORE_EXTENSIONS_PATH and THIRDPARTY_EXTENSIONS_PATH.
  *
  * @todo see coding style for methods!!
  */
@@ -78,16 +78,17 @@ class Minz_ExtensionManager {
 	 * inherit from Minz_Extension class.
 	 */
 	public static function init() {
-		$list_potential_extensions = array_values(array_diff(
-			scandir(EXTENSIONS_PATH),
-			array('..', '.')
-		));
+		$list_core_extensions = array_diff(scandir(CORE_EXTENSIONS_PATH), [ '..', '.' ]);
+		$list_thirdparty_extensions = array_diff(scandir(THIRDPARTY_EXTENSIONS_PATH), [ '..', '.' ], $list_core_extensions);
+		array_walk($list_core_extensions, function (&$s) { $s = CORE_EXTENSIONS_PATH . '/' . $s; });
+		array_walk($list_thirdparty_extensions, function (&$s) { $s = THIRDPARTY_EXTENSIONS_PATH . '/' . $s; });
+
+		$list_potential_extensions = array_merge($list_core_extensions, $list_thirdparty_extensions);
 
 		$system_conf = Minz_Configuration::get('system');
 		self::$ext_auto_enabled = $system_conf->extensions_enabled;
 
-		foreach ($list_potential_extensions as $ext_dir) {
-			$ext_pathname = EXTENSIONS_PATH . '/' . $ext_dir;
+		foreach ($list_potential_extensions as $ext_pathname) {
 			if (!is_dir($ext_pathname)) {
 				continue;
 			}
@@ -111,7 +112,7 @@ class Minz_ExtensionManager {
 
 			// Try to load extension itself
 			$extension = self::load($meta_json);
-			if (!is_null($extension)) {
+			if ($extension != null) {
 				self::register($extension);
 			}
 		}
diff --git a/lib/core-extensions/README.md b/lib/core-extensions/README.md
new file mode 100644
index 000000000..7d48fbffd
--- /dev/null
+++ b/lib/core-extensions/README.md
@@ -0,0 +1,5 @@
+# FreshRSS core extensions
+
+This directory contains some core extensions shipped with FreshRSS.
+
+For custom third-party extensions, use the `./FreshRSS/extensions/` directory instead.
diff --git a/lib/core-extensions/Tumblr-GDPR/README.md b/lib/core-extensions/Tumblr-GDPR/README.md
new file mode 100644
index 000000000..fc5e4dd50
--- /dev/null
+++ b/lib/core-extensions/Tumblr-GDPR/README.md
@@ -0,0 +1,4 @@
+# Tumblr-GDPR
+
+Needed for accessing [Tumblr](https://www.tumblr.com/) RSS feeds from the European Union:
+bypass the [GPDR](https://en.wikipedia.org/wiki/General_Data_Protection_Regulation) check, implying consent.
diff --git a/lib/core-extensions/Tumblr-GDPR/extension.php b/lib/core-extensions/Tumblr-GDPR/extension.php
new file mode 100644
index 000000000..83bdf2189
--- /dev/null
+++ b/lib/core-extensions/Tumblr-GDPR/extension.php
@@ -0,0 +1,13 @@
+<?php
+
+class TumblrGdprExtension extends Minz_Extension {
+	public function init() {
+		$this->registerHook('simplepie_before_init', array('TumblrGdprExtension', 'curlHook'));
+	}
+
+	public static function curlHook($simplePie, $feed) {
+		if (preg_match('#^https?://[a-zA-Z_0-9-]+.tumblr.com/#i', $feed->url())) {
+			$simplePie->set_useragent(FRESHRSS_USERAGENT . ' like Baiduspider');
+		}
+	}
+}
diff --git a/lib/core-extensions/Tumblr-GDPR/metadata.json b/lib/core-extensions/Tumblr-GDPR/metadata.json
new file mode 100644
index 000000000..b5c33787b
--- /dev/null
+++ b/lib/core-extensions/Tumblr-GDPR/metadata.json
@@ -0,0 +1,8 @@
+{
+	"name": "Tumblr-GDPR",
+	"author": "Alkarex",
+	"description": "Bypass Tumblr’ GPDR check (implying consent) for the European Union",
+	"version": 1.0,
+	"entrypoint": "TumblrGdpr",
+	"type": "system"
+}