Issue #11728: Add Fileinfo checks to admin/check/

Add some further checks to check_attachments_inc.php as part of the new
configuration/environment check script in 1.3.x to verify that Fileinfo
is configured correctly.

admin/check/check_attachments_inc.php

@@ -85,3 +85,32 @@
 		);
 	}
 }
+
+$t_finfo_exists = class_exists( 'finfo' );
+check_print_test_warn_row(
+	'Fileinfo extension is available for determining file MIME types',
+	$t_finfo_exists,
+	array( false => 'Web clients may struggle to download files without knowing the MIME type of each attachment.' )
+);
+
+if( $t_finfo_exists ) {
+	$t_fileinfo_magic_db_file = config_get_global( 'fileinfo_magic_db_file' );
+	if( $t_fileinfo_magic_db_file ) {
+		check_print_info_row(
+			'Name of magic.db file set with the fileinfo_magic_db_file configuration value',
+			config_get_global( 'fileinfo_magic_db_file' )
+		);
+		check_print_test_row(
+			'fileinfo_magic_db_file configuration value points to an existing magic.db file',
+			file_exists( $t_fileinfo_magic_db_file )
+		);
+		$t_finfo = new finfo( FILEINFO_MIME, $t_fileinfo_magic_db_file );
+	} else {
+		$t_finfo = new finfo( FILEINFO_MIME );
+	}
+	check_print_test_row(
+		'Fileinfo extension can find and load a valid magic.db file',
+		$t_finfo !== false,
+		array( false => 'Ensure that the fileinfo_magic_db_file configuration value points to a valid magic.db file.' )
+	);
+}