Aggregated entity fields cause SchemaIncompleteException

Problem/Motivation

While working on #2976147: Create a sales report supporting daily, weekly, monthly, and yearly breakdowns., my tests failed due to configuration schema validation.

Schema errors for views.view.sales_report with the following errors: views.view.sales_report:display.default.display_options.fields.report_id.set_precision missing schema

The report_id is the entity identifier base field. The View has aggregation enabled, and the report_id is set to COUNT.

In Views, the handler is swapped to numeric as an override when the display is built. This is causing a SchemaIncompleteException exception to be thrown.

This following code is what changes the handler and causes the schema error

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

        // If aggregation is on, the group type might override the actual
        // handler that is in use. This piece of code checks that and,
        // if necessary, sets the override handler.
        $override = NULL;
        if ($this->useGroupBy() && !empty($info['group_type'])) {
          if (empty($this->view->query)) {
            $this->view->initQuery();
          }
          $aggregate = $this->view->query->getAggregationInfo();
          if (!empty($aggregate[$info['group_type']]['handler'][$type])) {
            $override = $aggregate[$info['group_type']]['handler'][$type];
          }
        }

Proposed resolution

No idea.

Remaining tasks

• Write test which aggregates an entity ID
• ???

User interface changes

API changes

Data model changes