Example Dynamic node route in drupal 8.

example.info.yml

name: Example
type: module
description: Provides a homepage route based on a publish schedule date range field.
package: Example
core: 8.x

dependencies:
  - node

example.routing.yml

example.home:
  path: '/home'
  defaults:
    _controller: '\Drupal\node\Controller\NodeViewController::view'
    _title_callback: '\Drupal\node\Controller\NodeViewController::title'
  requirements:
    _entity_access: 'node.view'
  options:
    _route_enhancers: 'route_enhancer.example.homepage'

example.services.yml

services:
  route_enhancer.example.homepage:
    class: Drupal\example\Routing\Enhancer\HomepageEnhancer
    arguments: ['@entity.query', '@entity_type.manager']
    tags:
      - { name: route_enhancer }

ExampleHomepageResolverTest.php

<?php
/**
 * @file `tests/src/Kernel/ExampleHomepageResolverTest.php`
 *
 * Provides kernel tests for the HomepageEnhancer.
 */

namespace Drupal\Tests\example\Kernel;

use Drupal\Core\Datetime\DrupalDateTime;
use Drupal\datetime_range\Plugin\Field\FieldType\DateRangeItem;
use Drupal\field\Entity\FieldConfig;
use Drupal\field\Entity\FieldStorageConfig;
use Drupal\node\Entity\Node;
use Drupal\simpletest\ContentTypeCreationTrait;
use Drupal\simpletest\UserCreationTrait;
use Drupal\Tests\field\Kernel\FieldKernelTestBase;
use Symfony\Component\HttpFoundation\Request;

/**
 * Tests homepage resolution.
 *
 * @group example
 * @coversDefaultClass \Drupal\example\Routing\Enhancer\HomepageEnhancer
 */
class ExampleHomepageResolverTest extends FieldKernelTestBase {

  use UserCreationTrait;
  use ContentTypeCreationTrait;

  /**
   * A field storage to use in this test class.
   *
   * @var \Drupal\field\Entity\FieldStorageConfig
   */
  protected $fieldStorage;

  /**
   * The field used in this test class.
   *
   * @var \Drupal\field\Entity\FieldConfig
   */
  protected $field;

  /**
   * {@inheritdoc}
   */
  public static $modules = [
    'node',
    'datetime',
    'datetime_range',
    'example',
  ];

  /**
   * {@inheritdoc}
   */
  protected function setUp() {
    parent::setUp();

    $this->installEntitySchema('node');
    $this->installSchema('node', 'node_access');
    $this->installConfig('node');
    // Create a node type.
    $this->createContentType(array(
      'type' => 'homepage',
      'name' => 'Homepage',
      'display_submitted' => FALSE,
    ));

    // Add a datetime range field.
    $this->fieldStorage = FieldStorageConfig::create([
      'field_name' => 'field_schedule',
      'entity_type' => 'node',
      'type' => 'daterange',
      'settings' => ['datetime_type' => DateRangeItem::DATETIME_TYPE_DATE],
    ]);
    $this->fieldStorage->save();

    $this->field = FieldConfig::create([
      'field_storage' => $this->fieldStorage,
      'bundle' => 'homepage',
      'required' => TRUE,
    ]);
    $this->field->save();
  }

  /**
   * Tests the homepage resolves according to the date.
   */
  public function testHomepageResolver() {
    $this->fieldStorage->setSetting('datetime_type', DateRangeItem::DATETIME_TYPE_DATE);
    $field_name = $this->fieldStorage->getName();

    $start_date = new DrupalDateTime('-3 Days');
    $end_date = new DrupalDateTime('-2 Days');

    // Create an expired homepage node.
    $homepage_expired = Node::create([
      'title' => $this->randomMachineName(),
      'type' => 'homepage',
      $field_name => [
        'value' => $start_date->format(DATETIME_DATE_STORAGE_FORMAT),
        'end_value' => $end_date->format(DATETIME_DATE_STORAGE_FORMAT),
      ],
    ]);
    $homepage_expired->save();

    $start_date = new DrupalDateTime('-15 Days');
    $end_date = new DrupalDateTime('+15 Days');
    // Create a valid homepage node.
    $homepage_current = Node::create([
      'title' => $this->randomMachineName(),
      'type' => 'homepage',
      $field_name => [
        'value' => $start_date->format(DATETIME_DATE_STORAGE_FORMAT),
        'end_value' => $end_date->format(DATETIME_DATE_STORAGE_FORMAT),
      ],
    ]);
    $homepage_current->save();

    $authenticated_user = $this->createUser(['access content']);
    \Drupal::service('account_switcher')->switchTo($authenticated_user);

    $request = Request::create('/home');
    $kernel = \Drupal::getContainer()->get('http_kernel');
    $response = $kernel->handle($request);

    // Make sure access content is enough to see the homepage node.
    self::assertSame(200, $response->getStatusCode());
    // Make sure the current homepage is the one that resolves.
    self::assertSame($homepage_current->id(), $request->attributes->get('node')->id(), 'The homepage is resolved');

    // Used for text assertions.
    $this->setRawContent($response->getContent());

    // Make sure the correct title is rendered.
    $this->assertText($homepage_current->getTitle());
  }
}

HomepageEnhancer.php

<?php
/**
 * @file `src/Routing/Enhancer/HomepageEnhancer.php`
 *
 * The HomepageEnhancer class is responsible for supplying the current homepage
 * node that should be displayed dependent on the schedule.
 *
 * This module assumes the `homepage` content type with the `field_schedule`
 * daterange field has been created.
 */

namespace Drupal\example\Routing\Enhancer;

use Drupal\Core\Datetime\DrupalDateTime;
use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\Core\Entity\Query\QueryFactory;
use Drupal\Core\Routing\Enhancer\RouteEnhancerInterface;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\Route;

class HomepageEnhancer implements RouteEnhancerInterface {

  /**
   * The query factory.
   *
   * @var \Drupal\Core\Entity\Query\QueryFactoryInterface
   */
  protected $entity_query;

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entity_type_manager;

  /**
   * Constructs an HomepageEnhancer instance.
   *
   * @param \Drupal\Core\Entity\Query\QueryFactory $entity_query
   *   The entity resolver manager.
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   */
  public function __construct(QueryFactory  $entity_query, EntityTypeManagerInterface $entity_type_manager) {
    $this->entity_query = $entity_query;
    $this->entity_type_manager = $entity_type_manager;
  }

  /**
   * {@inheritdoc}
   */
  public function enhance(array $defaults, Request $request) {

    if (empty($defaults['node'])) {
      // Use a datetime object to get the current time.
      $now = new DrupalDateTime('now');
      $sql_time = $now->format(DATETIME_DATE_STORAGE_FORMAT);
      // Get the latest published homepage.
      $homepage_result = $this->entity_query->get('node')
        ->condition('type', 'homepage')
        ->condition('field_schedule', $sql_time, '<=')
        ->condition('field_schedule.end_value', $sql_time, '>=')
        ->condition('status', 1)
        ->sort('field_schedule', 'DESC')
        ->range(0,1)
        ->execute();

      $nid = reset($homepage_result);

      if (!empty($nid)) {
        // Get the Symfony route object.
        $route = $defaults[RouteObjectInterface::ROUTE_OBJECT];
        // If we don't set the default nid route match won't work meaning that access checks will fail and node context won't be available.
        $route->setDefault('node', $nid);
        // This is the enhancement part, setting the node object.
        $defaults['node'] = $this->entity_type_manager->getStorage('node')->load($nid);
      }
    }

    return $defaults;
  }

  /**
   * {@inheritdoc}
   */
  public function applies(Route $route) {
    // Only applies to the homepage route.
    return TRUE;
  }

}