From 4658220b2dc43c6a6c561afd2668bcd17cbd9ca5 Mon Sep 17 00:00:00 2001
From: Cameron Ball <cameron@moodle.com>
Date: Thu, 8 Feb 2018 13:32:04 +0800
Subject: [PATCH] MDL-61394 Administration: Add experimental feature to use
 SassC

---
 admin/settings/development.php |  2 ++
 lang/en/admin.php              |  2 ++
 lib/classes/scss.php           | 48 ++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/admin/settings/development.php b/admin/settings/development.php
index 80a804767df..e31a4542903 100644
--- a/admin/settings/development.php
+++ b/admin/settings/development.php
@@ -14,6 +14,8 @@ if ($hassiteconfig) { // speedup for non-admins, add all caps used on this page
 
     $temp->add(new admin_setting_configcheckbox('dndallowtextandlinks', new lang_string('dndallowtextandlinks', 'admin'), new lang_string('configdndallowtextandlinks', 'admin'), 0));
 
+    $temp->add(new admin_setting_configexecutable('pathtosassc', new lang_string('pathtosassc', 'admin'), new lang_string('pathtosassc_help', 'admin'), null));
+
     $ADMIN->add('experimental', $temp);
 
     // "debugging" settingpage
diff --git a/lang/en/admin.php b/lang/en/admin.php
index 4a49dd73aab..eb6030da540 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -837,6 +837,8 @@ $string['pathtopsqldesc'] = 'This is only necessary to enter if you have more th
 $string['pathtopsqlinvalid'] = 'Invalid path to psql - either wrong path or not executable';
 $string['pathtopython'] = 'Path to Python';
 $string['pathtopythondesc'] = 'Path to your executable Python binary (both Python 2 and Python 3 are acceptable).';
+$string['pathtosassc'] = 'Path to SassC';
+$string['pathtosassc_help'] = 'Specifying the location of the SassC binary will switch the SASS compiler from Moodle\'s PHP implementation to SassC. See https://github.com/sass/sassc for more information.';
 $string['pcreunicodewarning'] = 'It is strongly recommended to use PCRE PHP extension that is compatible with Unicode characters.';
 $string['perfdebug'] = 'Performance info';
 $string['performance'] = 'Performance';
diff --git a/lib/classes/scss.php b/lib/classes/scss.php
index a8aa4a9081e..0b13e49050f 100644
--- a/lib/classes/scss.php
+++ b/lib/classes/scss.php
@@ -98,6 +98,54 @@ class core_scss extends \Leafo\ScssPhp\Compiler {
         return $this->compile($content);
     }
 
+    /**
+     * Compile scss.
+     *
+     * Overrides ScssPHP's implementation, using the SassC compiler if it is available.
+     *
+     * @param string $code SCSS to compile.
+     * @param string $path Path to SCSS to compile.
+     *
+     * @return string The compiled CSS.
+     */
+    public function compile($code, $path = null) {
+        global $CFG;
+
+        $pathtosassc = trim($CFG->pathtosassc);
+
+        if (!empty($pathtosassc) && is_executable($pathtosassc) && !is_dir($pathtosassc)) {
+            $process = proc_open(
+                $pathtosassc . ' -I' . implode(':', $this->importPaths) . ' -s',
+                [
+                    ['pipe', 'r'], // Set the process stdin pipe to read mode.
+                    ['pipe', 'w'], // Set the process stdout pipe to write mode.
+                    ['pipe', 'w'] // Set the process stderr pipe to write mode.
+                ],
+                $pipes // Pipes become available in $pipes (pass by reference).
+            );
+            if (is_resource($process)) {
+                fwrite($pipes[0], $code); // Write the raw scss to the sassc process stdin.
+                fclose($pipes[0]);
+
+                $stdout = stream_get_contents($pipes[1]);
+                $stderr = stream_get_contents($pipes[2]);
+
+                fclose($pipes[1]);
+                fclose($pipes[2]);
+
+                // The proc_close function returns the process exit status. Anything other than 0 is bad.
+                if (proc_close($process) !== 0) {
+                    throw new coding_exception($stderr);
+                }
+
+                // Compiled CSS code will be available from stdout.
+                return $stdout;
+            }
+        }
+
+        return parent::compile($code, $path);
+    }
+
     /**
      * Compile child; returns a value to halt execution
      *