Make page loading faster by deferred script loading:

* Create generalized function for emmitting <script defer src=""> tags to templates
* Remove type attribute from inline_js
* Add defer attribute to external <script> tags

Signed-off-by: Michael Letzgus <michaelletzgus@users.noreply.github.com>

2 files changed, 41 insertions, 0 deletions

diff --git a/lib/private/legacy/template.php b/lib/private/legacy/template.php
index b4c69327438..4f7c11d0b64 100644
--- a/lib/private/legacy/template.php
+++ b/lib/private/legacy/template.php
@@ -12,6 +12,7 @@
  * @author Joas Schilling <coding@schilljs.com>
  * @author Jörn Friedrich Dreyer <jfd@butonic.de>
  * @author Lukas Reschke <lukas@statuscode.ch>
+ * @author Michael Letzgus <develope@michael-letzgus.de>
  * @author Morris Jobke <hey@morrisjobke.de>
  * @author Raghu Nayyar <hey@raghunayyar.com>
  * @author Robin Appelman <robin@icewind.nl>
@@ -208,6 +209,9 @@ class OC_Template extends \OC\Template\Base {
 			$headers = '';
 			foreach(OC_Util::$headers as $header) {
 				$headers .= '<'.\OCP\Util::sanitizeHTML($header['tag']);
+				if ( strcasecmp($header['tag'], 'script') === 0 && in_array('src', array_map('strtolower', array_keys($header['attributes']))) ) {
+					$headers .= ' defer';
+				}
 				foreach($header['attributes'] as $name=>$value) {
 					$headers .= ' '.\OCP\Util::sanitizeHTML($name).'="'.\OCP\Util::sanitizeHTML($value).'"';
 				}
diff --git a/lib/private/legacy/template/functions.php b/lib/private/legacy/template/functions.php
index 7814918b815..06eb512b54f 100644
--- a/lib/private/legacy/template/functions.php
+++ b/lib/private/legacy/template/functions.php
@@ -7,6 +7,7 @@
  * @author Joas Schilling <coding@schilljs.com>
  * @author Jörn Friedrich Dreyer <jfd@butonic.de>
  * @author Lukas Reschke <lukas@statuscode.ch>
+ * @author Michael Letzgus <develope@michael-letzgus.de>
  * @author Morris Jobke <hey@morrisjobke.de>
  * @author Robin McCorkell <robin@mccorkell.me.uk>
  * @author Roeland Jago Douma <roeland@famdouma.nl>
@@ -38,6 +39,42 @@ function p($string) {
 }
 
 /**
+ * Prints a <script> tag with nonce and defer depending on config
+ * @param string $src the source URL, ignored when empty
+ * @param string $script_content the inline script content, ignored when empty
+ * @param bool $defer_flag deferred loading or not
+*/
+function emit_script_tag($src, $script_content) {
+	$defer_str=' defer';
+	$s='<script nonce="' . \OC::$server->getContentSecurityPolicyNonceManager()->getNonce() . '"';
+	if (!empty($src)) {
+		 // emit script tag for deferred loading from $src
+		$s.=$defer_str.' src="' . $src .'">';
+	} else if (!empty($script_content)) {
+		// emit script tag for inline script from $script_content without defer (see MDN)
+		$s.=">\n".$script_content."\n";
+	} else {
+		// no $src nor $src_content, really useless empty tag
+		$s.='>';
+	}
+	$s.='</script>';
+	print_unescaped($s."\n");
+}
+
+/**
+ * Print all <script> tags for loading JS
+ * @param hash $obj all the script information from template
+*/
+function emit_script_loading_tags($obj) {
+	if (!empty($obj['inline_ocjs'])) {
+		emit_script_tag('', $obj['inline_ocjs']);
+	}
+	foreach($obj['jsfiles'] as $jsfile) {
+		emit_script_tag($jsfile, '');
+	}
+}
+
+/**
  * Prints an unsanitized string - usage of this function may result into XSS.
  * Consider using p() instead.
  * @param string|array $string the string which will be printed as it is