Price fields do not work properly when using SUM/AVG aggregation functions

In commerce_price.views.inc

      $data[$table_name][$field_name . '_number']['field'] = [
        'id' => 'numeric',
        'field_name' => $table_data[$field_name]['field']['field_name'],
        'entity_type' => $table_data[$field_name]['field']['entity_type'],
        'label' => t('number from @field_name', ['@field_name' => $field_name]),
      ];

The number field is marked to use the numeric field. When aggregating I am guessing that Views will default to the "first" field property as being the "real field", which is *_number. So on aggregation it sums to amount and it is rendering it using the numeric field handler.

Looks like we'll need to provide a custom handler.

It might be more than that.

In \Drupal\views\Plugin\views\query\Sql::getAggregationInfo the aggregate options define the field handler.

      'sum' => [
        'title' => $this->t('Sum'),
        'method' => 'aggregationMethodSimple',
        'handler' => [
          'argument' => 'groupby_numeric',
          'field' => 'numeric',
          'filter' => 'groupby_numeric',
          'sort' => 'groupby_numeric',
        ],
      ],

Okay, so by picking any form of aggregate function it overrides the price field to be a Numeric handler and not even EntityField.

There's no way to override the handler...easily.

In \Drupal\views\Plugin\views\display\DisplayPluginBase::getHandlers

          $aggregate = $this->view->query->getAggregationInfo();
          if (!empty($aggregate[$info['group_type']]['handler'][$type])) {
            $override = $aggregate[$info['group_type']]['handler'][$type];
          }

The handler is overridden from that aggregation info. We would have to create a new display plugin which attempted to override this, using its own handler to support SUM on the field while GROUP on the currency code.

This looks to be blocked, partially, by core #2975149: When using aggregation, additional fields should not be included in the grouping function

Here is a patch which implements the core patch fix to commerce_order_report views. It unsets aggregate functions to additional fields added in. Now we need to fix the formatting, which should be possible since we are grouping by the currency code, now.

Okay, it looks like we can't format the output in the pre_render Views hook. The \Drupal\views\Plugin\views\field\NumericField::render method calls $value = round($value, $precision); which causes the formatter price to return 0.

This makes it work! Swaps out the field handler later on.

Whoops, that had other cruft in it.

+++ b/commerce_reports.module
@@ -10,3 +15,62 @@ function commerce_reports_query_commerce_reports_alter(AlterableInterface $query
+  // Swap out the NumericField handler with our special Price one.
+  $view->field['amount'] = \Drupal\commerce_reports\Plugin\views\field\PriceNumericField::createFromNumericField(
+    $view->field['amount']
+  );

Forgot I didn't make this dynamic and just hardcoded it for testing.

Using an array_intersect we can check if there are matching additional fields and determine the price fields.

      $intersect_test = array_intersect([
        $field_plugin->field . '_number',
        $field_plugin->field . '_currency_code'
      ], $field_plugin->additional_fields);

      if (!empty($intersect_test)) {
        // Swap out the NumericField handler with our special Price one.
        $view->field[$key] = PriceNumericField::createFromNumericField($field_plugin);
      }

Committed.