From bfa46dd34db6f6d399b7dd80eea888df0b98310a Mon Sep 17 00:00:00 2001
From: anton-mellit <mellit@gmail.com>
Date: Sun, 12 Apr 2020 18:00:52 +0200
Subject: [PATCH] Any form field can be equipped with the following: ```
 process:     twig: some twig markup goes here ``` Additionally, form is
 equipped with a new action "process". When process action is called, all
 process:twig contents of all fields are evaluated the results are saved in
 the values of these fields. For instance ``` form:     fields:         -     
        type: hidden             name: path             process:              
   twig: "/blog/{{ grav.page.folder }}"     process:         -            
 process: true         -             addComment: true ``` After the form is
 submitted, before saving the comment the field "path" is evaluated to
 /blog/{{ grav.page.folder }}

---
 form.php | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/form.php b/form.php
index 792fb471..e07af12e 100644
--- a/form.php
+++ b/form.php
@@ -384,9 +384,11 @@ public function onFormProcessed(Event $event)
         $action = $event['action'];
         $params = $event['params'];
 
-        $this->process($form);
-
         switch ($action) {
+            case 'process':
+                $this->process($form);
+                break;
+
             case 'captcha':
 
                 $captcha_config = $this->config->get('plugins.form.recaptcha');
@@ -857,6 +859,14 @@ protected function process($form)
             if (!empty($field['process']['fillWithCurrentDateTime'])) {
                 $form->setData($field['name'], gmdate('D, d M Y H:i:s', time()));
             }
+            if (!empty($field['process']['twig'])) {
+                $twig = $this->grav['twig'];
+                $vars = [
+                    'form' => $form
+                ];
+                // Process with Twig
+                $form->setData($field['name'], $twig->processString($field['process']['twig'], $vars));
+            }
         }
     }