Added new MoodleUtil::isLangFile() method

We are going to use it with the LangFilesOrdering Sniff
that needs to check when a given file is a lang one or no.

Author: stronk7

moodle/Tests/Util/MoodleUtilTest.php

@@ -480,6 +480,55 @@ protected function cleanMoodleUtilCaches() {
         $apiCache->setValue(null, []);
     }
 
+    /**
+     * Data provider for testIsLangFile.
+     *
+     * @return array
+     */
+    public static function isLangFileProvider(): array
+    {
+        return [
+            'Not in lang directory' => [
+                'value' => '/path/to/standard/file.php',
+                'return' => false,
+            ],
+            'In lang/en directory' => [
+                'value' => '/path/to/standard/lang/en/file.php',
+                'return' => true,
+            ],
+            'In lang directory but missing en' => [
+                'value' => '/path/to/standard/lang/file.php',
+                'return' => false,
+            ],
+            'In lang/en directory but missing .php' => [
+                'value' => '/path/to/standard/lang/en/file',
+                'return' => false,
+            ],
+            'In lang/en directory but another extension' => [
+                'value' => '/path/to/standard/lang/en/file.md',
+                'return' => false,
+            ],
+            'In lang sub-directory with not allowed chars' => [
+                'value' => '/path/to/standard/lang/@@@/file.php',
+                'return' => false,
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider isLangFileProvider
+     */
+    public function testIsLangFile(
+        string $filepath,
+        bool $expected
+    ): void {
+        $phpcsConfig = new Config();
+        $phpcsRuleset = new Ruleset($phpcsConfig);
+        $file = new File($filepath, $phpcsRuleset, $phpcsConfig);
+
+        $this->assertEquals($expected, MoodleUtil::isLangFile($file));
+    }
+
     /**
      * Data provider for testIsUnitTest.
      *

moodle/Util/MoodleUtil.php

@@ -442,6 +442,28 @@ public static function getMoodleRoot(?File $file = null, bool $selfPath = true):
         return self::$moodleRoot;
     }
 
+    /**
+     * Whether this file is a lang file.
+     *
+     * @param File $phpcsFile
+     * @return bool
+     */
+    public static function isLangFile(File $phpcsFile): bool
+    {
+        // If the file is not under a /lang/[a-zA-Z0-9_-]+/ directory, nothing to check.
+        // (note that we are using that regex because it's what PARAM_LANG does).
+        if (preg_match('~/lang/[a-zA-Z0-9_-]+/~', $phpcsFile->getFilename()) === 0) {
+            return false;
+        }
+
+        // If the file is not a PHP file, nothing to check.
+        if (substr($phpcsFile->getFilename(), -4) !== '.php') {
+            return false;
+        }
+
+        return true;
+    }
+
     /**
      * Whether this file is a unit test file.
      *