MDL-75353 mod_data: always return str in data_generate_default_template

From now on, the data_generate_default_template method will always return
a string with the template content or an empty string when there is no
content available (for instance, when the database has no fields).
This method won't return a boolean anymore.

mod/data/lib.php

@@ -606,15 +606,16 @@ class data_field_base {     // Base class for Database Field Types (see field/*/
  * @param int $recordid the entry record
  * @param bool $form print a form instead of data
  * @param bool $update if the function update the $data object or not
- * @return bool|string the template content.
+ * @return string the template content or an empty string if no content is available (for instance, when database has no fields).
  */
 function data_generate_default_template(&$data, $template, $recordid = 0, $form = false, $update = true) {
     global $DB;
 
-    if (!$data && !$template) {
-        return false;
+    if (!$data || !$template) {
+        return '';
     }
 
+    // These templates are empty by default (they have no content).
     $defaulttemplates = [
         'csstemplate',
         'jstemplate',
@@ -626,7 +627,8 @@ function data_generate_default_template(&$data, $template, $recordid = 0, $form
         return '';
     }
 
-    // get all the fields for that database
+    // Get all the fields for that database.
+    $str = '';
     if ($fields = $DB->get_records('data_fields', array('dataid'=>$data->id), 'id')) {
 
         $table = new html_table();
@@ -675,7 +677,6 @@ function data_generate_default_template(&$data, $template, $recordid = 0, $form
             $table->data[] = $row;
         }
 
-        $str = '';
         if ($template == 'listtemplate'){
             $str .= '##delcheck##';
             $str .= html_writer::empty_tag('br');
@@ -695,10 +696,10 @@ function data_generate_default_template(&$data, $template, $recordid = 0, $form
             $DB->update_record('data', $newdata);
             $data->{$template} = $str;
         }
+    }
 
     return $str;
 }
-}
 
 /**
  * Build the form elements to manage tags for a record.

mod/data/tests/externallib_test.php

@@ -513,6 +513,18 @@ class externallib_test extends externallib_advanced_testcase {
      */
     public function test_get_entries() {
         global $DB;
+
+        // Check the behaviour when the database has no entries.
+        $result = mod_data_external::get_entries($this->database->id);
+        $result = \external_api::clean_returnvalue(mod_data_external::get_entries_returns(), $result);
+        $this->assertEmpty($result['entries']);
+
+        $result = mod_data_external::get_entries($this->database->id, 0, true);
+        $result = \external_api::clean_returnvalue(mod_data_external::get_entries_returns(), $result);
+        $this->assertEmpty($result['entries']);
+        $this->assertEmpty($result['listviewcontents']);
+
+        // Add a few fields to the database.
         list($entry11, $entry12, $entry13, $entry14, $entry21) = self::populate_database_with_entries();
 
         // First of all, expect to see only my group entries (not other users in other groups ones).

mod/data/tests/lib_test.php

@@ -24,6 +24,8 @@
  */
 namespace mod_data;
 
+use stdClass;
+
 defined('MOODLE_INTERNAL') || die();
 
 global $CFG;
@@ -1968,4 +1970,73 @@ class lib_test extends \advanced_testcase {
         );
         $generator->create_instance($params);
     }
+
+    /**
+     * Test for data_generate_default_template(). This method covers different scenarios for checking when the returned value
+     * is empty or not, but doesn't check if the content has the expected value when it's not empty.
+     *
+     * @covers ::data_generate_default_template
+     */
+    public function test_data_generate_default_template(): void {
+        $this->resetAfterTest();
+        $this->setAdminUser();
+
+        $course = $this->getDataGenerator()->create_course();
+        $activity = $this->getDataGenerator()->create_module(manager::MODULE, ['course' => $course]);
+
+        // Check the result is empty when $data and/or $template are null.
+        $nullactivity = null;
+        $result = data_generate_default_template($nullactivity, 'listtemplate', 0, false, false);
+        $this->assertEmpty($result);
+        $result = data_generate_default_template($activity, null, 0, false, false);
+        $this->assertEmpty($result);
+        $result = data_generate_default_template($nullactivity, null, 0, false, false);
+        $this->assertEmpty($result);
+
+        // Check the result is empty when any of the templates that are empty are given.
+        $emptytemplates = [
+            'csstemplate',
+            'jstemplate',
+            'listtemplateheader',
+            'listtemplatefooter',
+            'rsstitletemplate',
+        ];
+        foreach ($emptytemplates as $emptytemplate) {
+            $result = data_generate_default_template($activity, $emptytemplate, 0, false, false);
+            $this->assertEmpty($result);
+        }
+
+        $templates = [
+            'listtemplate',
+            'singletemplate',
+            'asearchtemplate',
+        ];
+        // Check the result is empty when the database has no entries.
+        foreach ($templates as $template) {
+            $result = data_generate_default_template($activity, $template, 0, false, false);
+            $this->assertEmpty($result);
+            $this->assertEmpty($activity->{$template});
+        }
+
+        // Add a field to the activity.
+        $fieldrecord = new stdClass();
+        $fieldrecord->name = 'field-1';
+        $fieldrecord->type = 'text';
+        $datagenerator = $this->getDataGenerator()->get_plugin_generator('mod_data');
+        $datagenerator->create_field($fieldrecord, $activity);
+
+        // Check the result is not empty when the database has no entries.
+        foreach ($templates as $template) {
+            $result = data_generate_default_template($activity, $template, 0, false, false);
+            $this->assertNotEmpty($result);
+            $this->assertEmpty($activity->{$template});
+        }
+
+        // Check the result is not empty when the database has no entries and the result is saved when $update = true.
+        foreach ($templates as $template) {
+            $result = data_generate_default_template($activity, $template, 0, false, true);
+            $this->assertNotEmpty($result);
+            $this->assertNotEmpty($activity->{$template});
+        }
+    }
 }

mod/data/upgrade.txt

@@ -15,6 +15,8 @@ information provided here is intended especially for developers.
   - is_directory_a_preset
 * mod_data_external::add_entry() function throws an error when trying to add an entry to a database with no field created.
 * data_user_can_add_entry() function returns false for any user if there is no field created on the database.
+* From now on, the data_generate_default_template method will always return a string with the template content or an empty
+  string when there is no content available.
 
 === 3.7 ===
 * External functions get_entries, get_entry and search_entries now return an additional field "tags" containing the entry tags.