Tighten validation of `experience_builder.generated_field_explicit_input_ux: prop_field_definitions.[%key].default_value`

Overview

In HEAD:

          default_value:
            # TRICKY: this MUST be a sequence, to allow for a multi-value default for `type: array` prop shapes.
            type: sequence
            label: 'Default values'
            sequence:
              type: field.value.[%parent.%parent.field_type]
            # @todo Add validation constraint because this is only *conditionally* nullable: if the SDC prop is optional
            nullable: true

This issue is about adding that missing validation.

Proposed resolution

Take inspiration from:

• XB's KeyForEverySdcProp validation constraint
• core's NotNull validation constraint

⇒

1. Add a new NotNullValueForEveryRequiredSdcProp validation constraint. That should be able to follow the lead of the logic for KeyForEverySdcProp's validator. However, that uses \Drupal\experience_builder\PropShape\PropShape::getComponentProps(), which only looks at shapes, not required vs optional. To do that, use
   

   assert($component_plugin instanceof Drupal\Core\Plugin\Component);
   $component_schema = $component_plugin->metadata->schema ?? [];
   $required_props = $component_schema['required'] ?? [];
   

   For each of $required_props, a key must exist in the sequence, and it must have a not-null value. That's the validation logic we need 😊

2. Add new ComponentValidationTest::testInvalidWidgetSettings() test that does
   

       $settings = $this->entity->getSettings();
       assert($settings['prop_field_definitions']['text']['default_value'] !== NULL);
       $settings['prop_field_definitions']['text']['default_value'] = NULL;
       $this->entity->setSettings($settings);
       $this->assertValidationErrors(['settings.prop_field_definitions.text.default_value' => 'a meaningfulerror message']);
   

User interface changes

None.