MDL-83430 customfield_number: call display method from provider earlier

customfield/field/number/classes/field_controller.php

@@ -173,6 +173,10 @@ class field_controller  extends \core_customfield\field_controller {
      * @return string|float|null
      */
     public function prepare_field_for_display(mixed $value, ?context $context = null): string|null|float {
+        if ($provider = provider_base::instance($this)) {
+            return $provider->prepare_export_value($value, $context);
+        }
+
         if ($value === null) {
             return null;
         }
@@ -185,17 +189,12 @@ class field_controller  extends \core_customfield\field_controller {
             }
         } else {
             // Let's format the value.
-            $provider = provider_base::instance($this);
-            if ($provider) {
-                $value = $provider->prepare_export_value($value, $context);
-            } else {
             $value = format_float((float)$value, $decimalplaces);
 
             // Apply the display format.
             $format = $this->get_configdata_property('display') ?? '{value}';
             $value = str_replace('{value}', $value, $format);
         }
-        }
 
         return format_string($value, true, ['context' => $context ?? system::instance()]);
     }

customfield/field/number/classes/local/numberproviders/nofactivities.php

@@ -157,13 +157,20 @@ class nofactivities extends provider_base {
     /**
      * Preparation for export for number of activities provider.
      *
-     * @param mixed $value String or float
+     * @param mixed $value String or float or null if the value is not present in the database for this instance
      * @param \context|null $context Context
      * @return ?string
      */
     public function prepare_export_value(mixed $value, ?\context $context = null): ?string {
-        if (trim((string)$value) === '') {
+        if ($value === null) {
             return null;
+        } else if (round((float)$value) == 0) {
+            $whenzero = $this->field->get_configdata_property('displaywhenzero');
+            if ((string) $whenzero === '') {
+                return null;
+            } else {
+                return format_string($whenzero, true, ['context' => $context ?? \core\context\system::instance()]);
+            }
         } else {
             return format_float((float)$value, 0);
         }

customfield/field/number/classes/provider_base.php

@@ -80,14 +80,34 @@ abstract class provider_base {
     }
 
     /**
-     * Provider specific value preparation for export.
+     * How the field should be displayed
+     *
+     * Called from {@see field_controller::prepare_field_for_display()}
+     * The return value may contain safe HTML but all user input must be passed through
+     * format_string/format_text functions
      *
      * @param mixed $value String or float
      * @param context|null $context Context
-     * @return ?string
+     * @return ?string null if the field should not be displayed or string representation of the field
      */
     public function prepare_export_value(mixed $value, ?\context $context = null): ?string {
-        return $value;
+        if ($value === null) {
+            return null;
+        }
+
+        // By default assumes that configuration 'decimalplaces' and 'displaywhenzero' are
+        // present. If they are not used in this provider, override the method.
+        $decimalplaces = (int) $this->field->get_configdata_property('decimalplaces');
+        if (round((float) $value, $decimalplaces) == 0) {
+            $result = $this->field->get_configdata_property('displaywhenzero');
+            if ((string) $result === '') {
+                return null;
+            } else {
+                return format_string($result, true, ['context' => $context ?? \core\context\system::instance()]);
+            }
+        } else {
+            return format_float((float)$value, $decimalplaces);
+        }
     }
 
     /**